Pe d i a t r i c I m a g i n g • R ev i ew Ghadimi Mahani et al. MRI of Pediatric Cardiac Masses
FOCUS ON:
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Pediatric Imaging Review
Maryam Ghadimi Mahani1 Jimmy C. Lu2 Cynthia K. Rigsby 3 Rajesh Krishnamurthy4 Adam L. Dorfman2 Prachi P. Agarwal1 Ghadimi Mahani M, Lu JC, Rigsby CK, Krishnamurthy R, Dorfman AL, Agarwal PP
Keywords: cardiac MRI, pediatric cardiac tumor DOI:10.2214/AJR.13.10680 Received February 1, 2013; accepted after revision October 13, 2013. 1 Department of Radiology, C. S. Mott Children’s Hospital, 1540 E Hospital Dr, SPC 4252, Ann Arbor, MI 48109-4252. Address correspondence to M. Ghadimi Mahani ([email protected]). 2 Department of Pediatrics, Division of Cardiology, C. S. Mott Children’s Hospital, Ann Arbor, MI. 3 Department of Medical Imaging, Ann and Robert H. Lurie Children’s Hospital of Chicago, Chicago, IL. 4 Departments of Radiology and Pediatrics, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX.
Supplemental Data Available online at www.ajronline.org. AJR 2014; 202:971–981 0361–803X/14/2025–971 © American Roentgen Ray Society
MRI of Pediatric Cardiac Masses OBJECTIVE. The purpose of this article is to describe the characteristic cardiac MRI features of primary and secondary cardiac tumors, including differentiation from masslike lesions, such as thrombus or focal myocardial hypertrophy. CONCLUSION. The frequency and type of cardiac tumors in children differ from those in adults. Although transthoracic echocardiography is the initial imaging technique of choice for evaluation of cardiac tumors, cardiac MRI is an important complementary modality for characterization of the mass and effect on cardiac function.
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ardiac tumors are rare, with a reported prevalence range of 0.0017–0.28% in autopsy series for all ages [1, 2]. The frequency and type of cardiac tumors in children differ from adults. The prevalence of pediatric primary cardiac tumors has been reported as 0.08% in infants and children under 5 years old by one institute during a 20-year interval [2–4]; the incidence of cardiac tumors detected by fetal echocardiography has been reported as 0.14% [1]. Pediatric cardiac tumors are being diagnosed more frequently with increased use of noninvasive imaging modalities, such as fetal echocardiography and MRI. Although cardiac tumors are rare, familiarity with the imaging appearance is important to distinguish cardiac neoplasms from other common masses, such as thrombi. Furthermore, despite the varied histologic types, cardiac MRI has been shown to be predictive of the tumor type on the basis of imaging characteristics [2]. Among pediatric cardiac neoplasms, secondary tumors are more common than primary tumors. Most primary pediatric cardiac tumors are benign, with only about 10% malignant [5]. Cardiac tumors can be asymptomatic and discovered incidentally during fetal anatomic imaging, by ultrasound, or during fetal MRI. When symptomatic, tumors can present in fetal life with hydrops, congestive heart failure, arrhythmia, and even stillbirth or in postnatal life with decreased cardiac output (due to ventricular inflow or outflow obstruction), cyanosis, murmur, myocardial dysfunction,
respiratory distress, valvular insufficiency, arrhythmia, thromboembolic events, and rarely sudden death [5]. The treatment of symptomatic cardiac tumors is surgical resection; sometimes palliative surgical debulking of the mass can be performed to relieve symptoms. The mainstay of imaging cardiac tumors is echocardiography. ECG-gated CT also enables assessment of cardiac masses, although it is generally less favored, particularly in the pediatric age group, because of concern for ionizing radiation. In addition, CT has lower temporal resolution compared with echocardiography and MRI. Cardiac MRI offers a noninvasive alternative for comprehensive cardiac assessment, including tissue characterization and evaluation of tumor size, extent, and physiologic impact [2]. Additionally, MRI provides better soft-tissue contrast resolution compared with both echocardiography and CT. Tissue sampling remains the reference standard for diagnosis but may not be necessary in all cases. This article will review the MRI protocol for comprehensive cardiac mass assessment, describe the spectrum of MRI appearances of pediatric cardiac tumors and masslike lesions, and elucidate the relevant key features that can help characterize a mass. Suggested MRI Protocol for Evaluation of the Cardiac Mass The first step in planning a cardiac MRI examination and determining the optimal imaging planes is to review any available imaging. Table 1 summarizes our institutional protocol for evaluation of pediatric cardiac masses. We
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Ghadimi Mahani et al. TABLE 1: Suggested MRI Protocol for Evaluation of Cardiac Masses at Our Institution Pulse Sequence
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Technical Parameters
Utility and Characteristics
Cine steady-state free precession imaging in multiple planes
TR/TE, 3.0/1.5; FOV, 250 × 150 mm (depending on the size of the patient); slice thickness, 6–7 mm; gap, 0 mm; flip angle, 60°; 30 phases per cardiac cycle. Various planes of acquisition can be used based on location of the lesion, such as axial, two- chamber left, two-chamber right, four-chamber, horizontal long-axis, short-axis, right ventricular outflow tract, and left ventricular outflow tract. The best plane is decided after reviewing any prior studies, such as echocardiography. If no prior studies are available, an axial stack of cine MRI is obtained, which helps decide optimal plane of imaging.
High temporal and contrast resolution and signal-to-noise ratio to assess tumor location, potential effect on function and blood flow, and mobility of the mass, in multiple planes
Double inversion-recovery T1-weighted turbo spin-echo imaging
TR/TE, 1 beat/10; flip angle, 90°; number of signals acquired, 2; slice thickness, 5 mm (based on tumor and patient size and can be decreased to 3 mm as needed); matrix, 200 × 194; FOV, 250 × 150 mm (depending on patient size); inversion time, 350 ms; black blood thickness, 10 mm
Helps in tissue characterization; better delineation of mass and relation to adjacent structures
T1-weighted imaging with SPIR fat suppression
Same as double inversion-recovery T1-weighted turbo spin-echo Helps in evaluation of fat in the lesion imaging with added fat-saturation prepulse, SPIR
T2-weighted STIR turbo spin-echo imaging
TR/TE, 2 beats/70; flip angle, 90°; FOV, 300 × 300 mm; matrix, 200 × 153; slice thickness, 6–8 mm; number of signals acquired, 1; added fat-saturation STIR
Helps in tissue characterization; evaluates presence of fat in the lesion; evaluates for presence of edema
First-pass perfusion imaging
TR/TE, 2.3/1.15; FOV, 250 × 178 mm; slice thickness, 10 mm; number of slices, 3; matrix, 96 × 69 mm; flip angle, 50°; contrast administration, 3 mL/ s using 0.1 mmol/kg IV gadolinium
Evaluates vascularity, as well as presence and pattern of lesion enhancement and helps in differentiation from thrombus
Gadolinium-enhanced double inversion-recovery T1- weighted turbo spin-echo imaging immediately after contrast injection
Usually 2–3 minutes after perfusion scanning; decrease inversion time and black blood pulse slice thickness to 5 mm, otherwise exactly the same parameters as before contrast injection
Evaluates enhancement of lesion; hyperenhancement favors vascular or malignant tumor; mild contrast enhancement is seen in 40–50% of benign tumors
Scout T1-weighted TI imaging (Look-Locker)
TR/TE, 8.1/3.0; matrix, 104 × 84; flip angle, 12°; one slice repeated Allows identification of optimal TI by visual inspection 41 times; slice thickness, 10 mm; incremental increase in TI starting from 125 ms
Late gadolinium-enhanced TR/TE, 6.1/3.0; 2D segmented inversion-recovery–prepared imaging 10 min after injection fast gradient-echo sequence with TE, 3 ms; flip angle, 25°; of contrast material, average number of slices, 8–12; slice thickness, 6–8 mm. TI is segmented double inversiondetermined using Look-Locker sequence, which is performed recovery fast spin-echo in perpendicular planes in which mass is best visualized.
For presence and pattern of enhancement, myocardial scar, and differentiation from thrombus, specifically with long inversion time (600ms)
Phase contrast imaging (optional)
Phase contrast imaging perpendicular to inflow (atrioventricular valve) or outflow tract of the ventricles (above aortic or pulmonic valves) can be performed to calculate flow volumes and regurgitation; depending on location of tumor, in-plane phase contrast imaging may be helpful to assess for increased velocity
2D fast-field echo with TR/TE, 4.6/2.8; flip angle, 12°; slice thickness, 6 mm; number of signals acquired, 3; heart phases, 40; phase contrast velocity, 150–250 cm/s
Note— SPIR = spectral presaturation with inversion-recovery.
use a cumulative dose of 0.1–0.2 mmol/kg IV of a gadolinium contrast agent. First-pass perfusion imaging is acquired dynamically during contrast injection, and, subsequently, late gadolinium-enhanced images are acquired 10 minutes after contrast injection. We use a 2D cine steady-state free precession (SSFP) sequence in appropriate imaging planes to assess for tumor size and motion with the cardiac cycle and potential impedance to flow and cardiac function (Fig. 1). Black blood imaging (T1-weighted imaging with and without fat suppression and T2-weighted imaging with fat suppression) as well as enhancement of the mass using first-pass perfusion imaging
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and delayed enhancement are used for mass characterization. When differentiation from thrombus is necessary, delayed enhancement with a long inversion time (600 ms) is preferred. Additional sequences can be used on the basis of the precise clinical question, such as 3D SSFP (particularly for assessing relationship to coronary arteries), MR angiography (MRA) for relationship to vascular structures, and flow velocity mapping for assessing impedance to blood flow. Pediatric Cardiac Tumors This article will focus mainly on primary cardiac neoplasms and their mimics. Imaging
Fig. 1—Screen capture from video of horizontal longaxis steady-state free precession cardiac video (see Fig. S1 in supplemental data online).
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Solitary or multiple, associated with tuberous sclerosis Solitary, well-defined border with thin rim of myocardium Cystic, multilobulated, pericardial effusion, tamponade, fetal hydrops
Pedunculated mobile mass with irregular border Intramural or endocardial
Usually solitary, multiple can be seen in association with other congenital heart disease Small in size; 1- to 2-mm, yellowish nodule on endocardium, epicardium, or valve Single unilocular cystic lesion
Irregular ill-defined border; pericardial or pleural involvement
Multiple, large pericardial effusion; no central necrosis Multiple lesions, large size, irregular ill-defined border; pericardial or pleural involvement
Fibroma
Teratoma
Myxoma
Hemangioma
Lipoma
Purkinje cell tumor
Pleuropericardial cyst
Rhabdomyosarcoma, symptoms associated with periradial and pleural disease and embolic phenomena
Lymphoma
Cardiac metastasis
Appearance and Characteristics
Rhabdomyoma
Tumor Type
Mostly right heart
Mostly involves right heart
Any chamber of the heart
Usually in right cardiophrenic angle; can be seen anywhere in mediastinum
Left ventricle and along conduction system
Mostly arises from epicardial surface; can involve all three layers of heart
Anywhere in heart; minimal predilection for ventricular septum and right atrium
Sporadic in left atrium, interatrial septum near fossa ovalis, familial in any chamber
Usually in pericardial cavity attached to pulmonary artery and aorta or arising from atrial or ventricular wall protruding into cardiac chamber
Intramyocardial ventricular septum or free wall
Intramyocardial or intracavitary, any chamber of the heart
Location
Heterogeneous
Homogeneous
Homogenous with occasional central necrosis
Homogeneous
Homogeneous
Heterogeneous
Heterogeneous, encapsulated, complex cystic mass
Heterogeneous
Homogeneous in all sequences
Imaging Characteristics on MRI
TABLE 2: Imaging Characteristics of Pediatric Cardiac Tumors
Hypointense
Iso- to slightly hypointense
Isointense
Hypointense; hyperintense if hemorrhagic or proteinaceous fluid
Hyperintense
Hyperintense, signal loss (hypointense) on fat-saturated sequence
Intermediate
Hypointense, hyperintense if proteinaceous
Isointense
T1-Weighted
Heterogeneous
Isointense
Hypointense
Hypointense
Hyperintense
Hypointense
Hypointense core with periphery isointense
Minimal hyperintense or variable
Contrast-Enhanced T1-Weighted
Hyperintense
Isointense
Hyperintense
Iso- or hypointense
Hyperintense
Hyperintense
Hyperintense
Mildly hyperintense
T2-Weighted
Pulse Sequence
Heterogeneous
Variable, minimal uptake
Hypointense
Hypointense
Variable, iso- to mildly hyperintense
Heterogeneous, variable
Hyperintense with or without dark center (hypointense)
Isointense
Late GadoliniumEnhanced
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MRI of Pediatric Cardiac Masses
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Ghadimi Mahani et al.
Primary Benign Pediatric Cardiac Tumors Most primary cardiac tumors are benign in children. These include rhabdomyoma, fibroma, teratoma, myxoma, hemangioma, and other rare tumors, with rhabdomyoma the most common [6, 7]. Rhabdomyoma—The most common benign pediatric cardiac tumor is rhabdomyoma, a hamartoma of the myocardium. It is frequently associated with tuberous sclerosis; half of the patients with rhabdomyomas also have tuberous sclerosis [8]. Partial or complete regression occurs in fetal life and in children less than 4 years old [1, 8, 9]. This fact coupled with a better survival of tuberous sclerosis patients without rhabdomyomas explains the decreased prevalence of this tumor with advancing age. Rhabdomyoma can be asymptomatic or may present with outflow tract obstruction, arrhythmia, and heart failure. In fetal life, presentation may be with hydrops fetalis or stillbirth. If asymptomatic, treatment is not needed because most tumors typically regress. If intervention is necessary, for instance in patients with left ventricular outflow tract obstruction or arrhythmia, the prognosis is good after excision. Rhabdomyomas are either intramyocardial or intracavitary and attached to the myocardium. On cardiac MRI, rhabdomyomas (Fig. 2) [2] are homogeneous on all sequences, mildly hyperintense on T2-weighted imaging, isointense to myocardium on T1weighted sequences, and show minimal or no
enhancement after administration of gadolinium-based contrast agents with hypointensity on first-pass perfusion imaging and isointensity on late gadolinium-enhanced sequences. Cardiac MRI and echocardiography are complementary modalities for diagnosing rhabdomyomas. Some rhabdomyomas detected with ultrasound may be missed with MRI, especially small (< 0.5 cm) or completely intramural lesions. However, MRI is superior to echocardiography in detecting intracavitary tumors and delineation of the extracardiac extension of the tumors [10]. MRI assessment of rhabdomyomas and other cardiac tumors is particularly helpful when surgical resection is being considered [11] because the anatomy and location of the mass or masses with respect to adjacent vital structures in the heart can be better evaluated with cardiac MRI. Fibroma—Cardiac fibroma is the second most common cardiac tumor in children and is typically located in the ventricular septum. These masses are derived from connective tissue fibroblasts and may invade the functional ventricular myocardium, resulting in congestive heart failure. They may also invade the conducting system and cause arrhythmia or even sudden cardiac death. Unlike rhabdomyomas, cardiac fibromas rarely regress, and surgery is often indicated. Partial resection may be the only option in patients with a widespread tumor that is not fully resectable [5, 8] (Fig. 3). Calcification within the center of the mass reflects poor blood supply and is considered pathognomonic for fibroma [5, 12]. Calcification is seen in 50% of pathologic specimens;
however, the radiographic evidence of tumor calcification is seen in 25% of cases [8] (Fig. 3). On CT, the tumor is seen as a heterogeneous mural mass with areas of calcification. Although cardiac fibroma usually occurs in isolation, there is increased risk of cardiac fibroma in patients with Gorlin syndrome (basal cell nevus syndrome, which is characterized by multiple nevoid basal cell carcinomas of skin, mandibular cysts, and bifid ribs) [13]. Cardiac fibroma also has a rare association with familial adenomatous polyposis and its subtype Gardner syndrome [14, 15]. The characteristic features of cardiac fibromas have been described as follows [2] (Fig. 3): usually solitary intramyocardial mass with well-defined borders involving the ventricular septum or free wall with a heterogeneous appearance and variable areas of mildly hypo- or hyperintense signal on T1-weighted and T2weighted sequences, hypointense on first-pass perfusion imaging, and hyperenhancement on late gadolinium-enhanced sequences with or without a hypoenhancing (dark) center. On MRA, fibromas have also been described to have a strongly hypointense core with isointense shell at the periphery [2, 16]. Fibromas associated with familial polyposis syndrome have also been seen in atria [15]. Areas of calcification can be seen as signal voids on MRI; however, in general, MRI is less sensitive compared with CT in detecting areas of calcification. Teratoma—Cardiac teratoma is an extremely rare tumor in the pediatric population [17]. It is usually extracardiac, located in the pericardium, and attached to the root
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characteristics of cardiac masses on specific pulse sequences are summarized in Table 2.
Fig. 2—Rhabdomyoma in 1-day-old boy with prenatal diagnosis of cardiac tumor. A–C, Cardiac MR images show that mass (arrow) arises from lateral wall of left ventricle and is isointense to myocardium on T1-weighted images without fat saturation before (not shown) and after contrast administration (A), mildly hyperintense on T2-weighted fat-saturated image (B), and isointense on late gadolinium-enhanced image (C). Patient remained asymptomatic. These features are most consistent with rhabdomyoma.
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MRI of Pediatric Cardiac Masses Fig. 3—Cardiac fibroma in 13-month-old girl under workup for prominent heart murmur. A, After abnormal echocardiogram that showed large heterogeneous probably calcified mass compressing right ventricular outflow tract, frontal chest radiograph obtained before cardiac MRI shows heterogeneous calcification in region of ventricle (arrow). B–D, Patient underwent cardiac MRI for further evaluation, which revealed large mass (arrows) involving right ventricular outflow tract and free wall of right ventricle. Mass has well-defined border and is mainly isointense to hypointense on T1-weighted sequence (B) and heterogeneous and mainly hyperintense with hypointense areas on T2weighted sequence with fat saturation (C). Mass is in close relationship to right coronary artery, and 3D steady-state free precession image (D) shows right coronary artery in right atrioventricular groove directly over mass. E, Late gadolinium-enhanced image shows peripheral late gadolinium enhancement (black arrow), with dark core of hypoenhancement (white arrow).
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of the aorta and pulmonary trunk. It rarely involves the myocardium, presenting as an intracardiac mass arising from the atrial or ventricular wall [18] (Fig. 4). Pericardial teratoma is easily detected by fetal echocardiography as a heterogeneous and encapsulated cystic mass, typically positioned on the right side of the heart [8]. Associated pericardial effusion is frequent [19, 20]. Teratomas involving the anterior mediastinum may grow rapidly. Chest radiography may reveal an enlarged cardiomediastinal silhouette and rarely may show calcification or formed teeth [8]. Macroscopically, teratomas have cystic and solid components with a multilocular appearance (Fig. 5). Microscopically, teratomas contain elements derived from all three germ layers. The main clinical findings result from mass effect of the tumor on the heart and
Fig. 4—Intramyocardial teratoma in 10-day-old girl with tachypnea, harsh murmur, and cardiomegaly. A and B, Cardiac MR images obtained after abnormal echocardiogram show multicystic mass invading entire interventricular septum (arrow, A) on short-axis steady-state free precession image (A). First-pass perfusion image (B) shows septal mass of decreased signal intensity without significant perfusion (arrows, B).
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Ghadimi Mahani et al. from the associated pericardial effusion. Fetal hydrops and stillbirth have been reported [5]. Surgical total or partial resection of teratoma has a favorable outcome [21]. The characteristic features include multilocular mass with cystic and solid components usually in intrapericardial location compressing the superior vena cava or right atrium (Fig. 5). They show heterogeneous signal intensity on T1-weighted and T2weighted sequences with areas of high signal intensity on T2-weighted imaging and hypointensity on first-pass perfusion imaging. Myxoma—Although myxoma is the most common primary benign tumor in adults, typically presenting between the fourth and seventh decades [22], it rarely occurs in children [23]. Myxoma can occur sporadically or may be seen in association with syndromes. The sporadic forms are more common in females [24] and in the left atrium, although myxoma can also occur in the right atrium [25] or in the ventricles. There is a predilection for the interatrial septum, in a region near the fossa ovalis [26] (Fig. 6). A small percentage (7%) of myxomas are syndromic. In these cases, tumors are multifocal, seen in chambers of the heart other than the left atrium, have a higher recurrence rate after surgical resection, and are more often seen in males and at younger ages. There may also be a familial predisposition for cardiac myxoma [27]. Clinical presentations of cardiac myxoma include breathlessness, syncope, embolism, congestive heart failure, arrhythmia, and constitutional symptoms. Right-sided myxomas are rare and can cause pulmonary embolism, tricuspid and pulmonary artery ob-
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Fig. 5—Pericardial teratoma in 13-year-old boy. A and B, Pericardial teratoma presenting as large multicystic tumor (arrows) appears mildly hyperintense on echo-planar T1-weighted image (A) due to proteinaceous-mucinous content, hyperintense on T2-weighted owing sequence (not shown), and with eccentric enhancement of solid component along medial aspect of tumor along with enhancement of septa on gadolinium-enhanced coronal echo-planar T1-weighted image (B). There is extrinsic mass effect on lateral wall of right atrium and cavoatrial junction.
struction, and right-heart failure [5]. Because the presenting symptoms can be nonspecific, myxomas may be clinically unsuspected and diagnosed late. Surgical resection has a favorable outcome with minimal or no recurrence. The characteristic features include pedunculated mobile mass with irregular borders commonly arising from the leftward aspect of the interatrial septum, hyperintensity on T2-weighted sequences (Fig. 6), heterogeneous enhancement with predominantly hypointensity on first-pass perfusion sequences, and iso- to hyperintense areas on late gadolinium-enhanced sequences. Hemangioma—Hemangiomas are rare benign vascular tumors that affect all age
groups [8, 22] and can be located anywhere in the heart, with a minimal predilection for the ventricular septum and right atrium [5]. Hemangiomas may be intramural or endocardial and can present as subendocardial nodules in the size range of 2–4 cm [28]. Cardiac hemangiomas are microscopically classified as cavernous, capillary, and arteriovenous. Clinically, hemangiomas are usually asymptomatic but can present with ventricular tachycardia, high-output cardiac failure, hemorrhage, pericardial effusion, cardiac tamponade, or thrombocytopenia [5]. Cardiac hemangiomas can be associated with hemangiomas in other sites, such as bowel, oral cavity, or skin [29].
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Fig. 6—Myxoma in 13-year-old boy. A–C, Cardiac MR images show myxoma as pedunculated oval-shaped mass (arrows) arising from interatrial septum and protruding superior to septal leaflet of mitral valve. Mass appears hyperintense on T2-weighted image (A), isointense to myocardium on echo-planar T1-weighted image (B), and with hyperintense rim enhancement on contrast-enhanced echo-planar T1-weighted image (C). RA = right atrium, RV = right ventricle, LV = left ventricle, LA = left atrium, VS = ventricular septum, AS = atrial septum, AO = aortic root.
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MRI of Pediatric Cardiac Masses Differentiation of hemangiomas from malignant vascular tumors may not be possible by MRI unless frank signs of invasion or metastases are seen [2]. Cardiac hemangiomas respond well to surgical excision if clinically necessary, such as when associated with obstructive symptoms [29–31]. Surgery is not necessary for asymptomatic hemangiomas because spontaneous regression has been reported [32]. The characteristic features include intermediate signal on T1-weighted and hyperintense signal on T2-weighted sequences, avid enhancement on first-pass perfusion sequences (Fig. 7) (a feature that will differentiate these from teratomas), and isointense or mildly hyperintense on late gadoliniumenhanced sequences. Lipoma—Lipomas have been reported in a wide age range of patients [33, 34] but are more common in adults. Most lesions arise from the epicardial surface; however, they can involve all three layers of the heart, including myocardium and endocardium [8, 22, 35]. Lipomas are usually solitary, but multiple lipomas have been reported in conjunction with congenital heart diseases, tuberous sclerosis, or sometimes sporadically in otherwise normal hearts [35, 36]. The characteristic features include homogeneous high signal intensity on T1weighted sequences, mildly hyperintense on T2-weighted sequences, loss of signal on fat suppression sequences, and no enhancement on first-pass perfusion sequences. Purkinje cell tumor—Purkinje cell tumor is considered a cardiac hamartoma [37] and has been described only in infants and children. It is distinct from rhabdomyoma and is known by different names, including foamy myocardial transformation of infancy, infantile xanthomatous cardiomyopathy, infantile cardiomyopathy with histiocytoid change, and histiocytoid cardiomyopathy in infancy [18]. Morphologically, it consists of focal collections of altered myocytes that are round and similar to histiocytes. Macroscopically, the tumor presents as yellowish nodules on the endocardium, epicardium, or valves ranging between 1–2 mm in size [38], with a propensity for the left ventricle and the conduction system [5]. Refractory arrhythmia is the most common clinical presentation [5, 39]. There are some reports of association with congenital heart disease, such as hypoplastic heart syndrome and atrial and ventricular septal defects [40], and with extracardiac anomalies [41].
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Fig. 7—13-year-old girl with septal mass noted on echocardiogram. A–D, Cardiac MR images show hemangioma (arrow), which is heterogeneous mass in ventricular septum mainly isointense to hypointense on axial T1-weighted image (A) and hyperintense on T2-weighted image with fat saturation (B), with enhancement on contrast-enhanced image (not shown). Septal mass (hemangioma) is hyperintense on T1-weighted late gadolinium-enhanced image (C) and shows strong enhancement on firstpass perfusion image (D).
The characteristic features include hyperintensity on T1-weighted sequences, isointensity to hypointensity on T2-weighted sequences, and no significant enhancement on first-pass perfusion sequences [2]. Other Benign Cardiac Tumors Papillary fibroelastomas—Papillary fibroelastomas are benign endocardial papillomas that predominantly affect the cardiac valves at a mean age of 60 years [42]. These tumors are very rare in children and manifest as pedunculated or mobile masses arising from endocardial cavity or valve on imaging [2]. Pleuropericardial cysts—Pleuropericardial cysts are benign congenital cystic lesions that arise from the pericardium but do not communicate with the pericardial space. They are most commonly found at the right cardiophrenic angle, but approximately one third of them can be found anywhere in the mediastinum. They are
usually unilocular simple cystic lesions with low signal intensity on T1-weighted sequences and high signal intensity on T2-weighted sequences with no enhancement on first-pass perfusion or contrast-enhanced sequences. Occasionally they contain proteinaceous material and have high signal intensity on both T1- and T2-weighted sequences [22, 43, 44]. Patients are usually asymptomatic, but approximately one third may complain of chest pain, dyspnea, or persistent cough [44]. Malignant Cardiac Tumors Malignant cardiac tumors are very rare in children and constitute a small proportion of cardiac masses, with 95% sarcomas (Fig. 8) and the rest lymphomas [5]. Cardiac sarcoma has several histologic subtypes, including angiosarcoma, rhabdomyosarcoma, malignant fibrous histiocytoma, undifferentiated sarcoma, and fibrosarcoma [45].
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Ghadimi Mahani et al. Secondary involvement of the heart by extracardiac primary malignancies is much more common than primary malignant cardiac tumors (Fig. 9). In the pediatric age group, metastases can be secondary to leukemia, lymphoma, Wilms tumor, hepatoblastoma, neuroblastoma, Ewing sarcoma, and osteosarcoma. Malignancies can involve the heart by lymphatic extension, hematogenous spread, or direct contiguous extension, or it can be spread via large vessels, such as the inferior vena cava [46]. The characteristic features of malignant cardiac tumors include heterogeneous signal intensity on all MRI sequences; infiltrative appearance crossing an annular or tissue plane within the heart or involving both cardiac and extracardiac structures, for example, extension to the mediastinum and great vessels; history of extracardiac malignancy (often present); arising from the right atrium; hemorrhagic pericardial effusion, and large size (more than 5 cm). It should be noted that none of the cardiac MRI features are very sensitive or specific for the diagnosis of the malignant cardiac masses [43]. Rhabdomyosarcoma—Rhabdomyosarcoma is the most common primary cardiac malignancy of childhood. There are two histologic subtypes of rhabdomyosarcoma: embryonal type, which is more common, and pleomorphic type, which is less frequent and mainly occurs in adults. There is no pre-
Fig. 9—Metastatic medulloblastoma in 12-year-old girl with known primary tumor in brain. Four-chamber gadolinium-enhanced echo-planar image shows heterogeneous enhancement of mass (arrow). Mass is centered on inferior atrial septum extending into crux of heart, encasing aortic annulus and septal leaflets of tricuspid and mitral valves, causing obstruction to atrioventricular valve inflow and aortic outflow. RA = right atrium, RV = right ventricle, LV = left ventricle, LA = left atrium, VS = ventricular septum, AS = atrial septum, AO = aortic root.
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Fig. 8—Primary cardiac sarcoma in 8-year-old boy. Axial T1-weighted image with fat saturation after IV administration of gadoliniumbased contrast agent shows infiltrating poorly defined mass (white arrow) centered on posterior atrial wall, with extension into pericardial cavity and heterogeneous enhancement. Associated malignant effusion of pericardium is also present with abnormal enhancement (black arrow). Small right pleural effusion is also seen (asterisk). RA = right atrium, RV = right ventricle, LV = left ventricle, LA = left atrium,
dilection for any specific cardiac chamber, although it more often involves the cardiac valves compared with other sarcomas and has a tendency to be multicentric [22, 43]. The characteristic features include a large infiltrative mass with irregular margin and central necrosis or cavitation, isointensity on T1-weighted sequences, hyperintensity in the center of the mass on T2-weighted sequences, heterogeneous enhancement on T1-weighted contrast-enhanced sequences because of central necrosis and cavitation, and peripheral hyperintensity on late gadolinium-enhanced sequences [22]. Primary cardiac lymphoma—Primary cardiac lymphoma is typically non-Hodgkin B cell type and is more common in adults and immunocompromised patients, with a mean age of 60 years and reported age range of 13–90 years [43]. Cardiac lymphoma is multicentric in 75% of cases and commonly involves the right side of the heart, especially the right atrium followed by the right ventricle, left ventricle, left atrium, atrial septum, and ventricular septum. There can be invasion of the pericardium, with possible massive pericardial effusion [8, 47]. The characteristic features include isointense to slightly hypointense on T1-weighted sequences, isointense on T2-weighted sequences, and minimal enhancement after gadolinium administration with areas of relatively lower enhancement in the center compared with the periphery [48, 49]. Nonneoplastic Cardiac Masses and Masslike Lesions Several cardiac lesions can mimic neoplasms on imaging. MRI can help facilitate differentiation and direct management.
Cardiac thrombus—Cardiac thrombus is by far the most common cardiac mass. Thrombi can occur in any cardiac chamber and are seen in the left atrial appendage in the setting of atrial fibrillation, in the right atrium in the presence of a central venous catheter, and in the ventricles (particularly the left) with aneurysmal dilatation after acute myocardial infarction. Although it should be noted that myocardial infarction is very rare in children, it can occur in some groups of children, for example, in anomalous origin of the left coronary artery, Kawasaki disease, idiopathic or congenital cardiomyopathies, nephrotic syndrome, and as a complication of surgical repair of congenital heart disease [50, 51]. The typical imaging appearance of a thrombus is that of a hypointense nonenhancing mass. The precise MRI characteristics depend on the age of the thrombus. Subacute thrombi are homogeneously low in signal intensity on gradient-echo sequences and do not enhance after gadolinium administration. However, organized chronic thrombi can be heterogeneous with intermediate signal intensity on gradient-echo sequences and with areas of enhancement after administration of contrast material, especially at the periphery because of the presence of vascular channels [52]. Differentiation of a cardiac thrombus from tumors, such as myxoma, can be difficult on echocardiography. Both lesions can occur in the left atrium and may be associated with atrial fibrillation. Low signal intensity and nonenhancement after gadolinium administration are useful clues that favor thrombus, although sometimes differentiation can be difficult. Late gadolinium-enhanced sequenc-
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MRI of Pediatric Cardiac Masses
Fig. 10—Short-axis late gadolinium-enhanced image in 12-year-old boy with osteosarcoma and right atrial thrombosis. Late gadolinium-enhanced cardiac MR image, which was obtained to evaluate right atrial mass seen on echocardiogram (not shown), shows lack of enhancement of thrombus (arrow).
es with a long inversion time (600 ms) can null the avascular tissue and have been found to be useful and sensitive for diagnosing thrombus. Thrombus will remain low in signal intensity, and myocardium and tumor may show an increase in signal intensity [53, 54]. The characteristic features include nonenhancing hypointense lesions on first-pass perfusion sequences, hypointensity on late gadolinium-enhanced sequences (Fig. 10), and hypointensity relative to the myocardium on late gadolinium-enhanced sequences with a long inversion time of 600 ms. Hypertrophic cardiomyopathy—Hypertrophic cardiomyopathy (HCM) is a myocardial disorder characterized by left ventricular hypertrophy in the absence of causes such as pressure overload or storage-infiltrative disease. The pathognomonic histologic features are myocyte disarray and fibrosis [55, 56]. HCM has a spectrum of manifestations, both clinically and morphologically. Clinical presentation ranges from asymptomatic to sudden cardiac death. Different morphologic imaging subtypes of HCM have been described in the literature, for example, asymmetric HCM with predominant involvement of the basal septum, HCM with midventricular obstruction (with or without a left ventricular apical diverticulum), apical HCM, symmetric (concentric) HCM, and masslike HCM. Sometimes HCM may present in the burned-out stage with focal or diffuse thinning of the myocardium. Right ventricular involvement occurs in 17.6% of cases of HCM [56, 57]. In many of its morphologic subtypes, particularly in the focal mass like
A
B
Fig. 11—17-year-old boy with idiopathic hypertrophic cardiomyopathy. A and B, Cardiac MR images show asymmetric masslike thickening of inferior interventricular septum and areas of hyperenhancement on late gadolinium-enhanced image (arrow, A) in short-axis plane. Note decreased contraction in area of hypertrophied myocardium compared with adjacent normal myocardium revealed by decreased distortion of tagging (arrows, B) compared with adjacent normal myocardium during systole.
type of HCM, the disorder can mimic a cardiac tumor (Fig. 11). MRI can help in differentiation of focal HCM from a true mass. The signal intensity of focal HCM follows that of the adjacent myocardium on the black blood and cine images with midmyocardial patchy areas of enhancement on late gadolinium-enhanced sequences. In contrast, cardiac tumors can be recognized by their characteristic appearance on MRI as detailed earlier. Additional sequences, such as myocardial tagging, can show decreased contractility compared with adjacent myocardium in the area of focal HCM with fibrosis; however, cardiac masses typically do not show any contractility. Further investigation to define the sensitivity and specificity of this application of cardiac MRI is still needed [58]. Future Directions in Cardiac Tumor Imaging Diffusion-weighted MRI (DWI) has been widely used in whole-body tumor imaging, but its utility in cardiac imaging is limited because of signal loss from cardiac motion. Recently, DWI has been used to differentiate pericardial cysts from other solid tumors [59]. However, further research is required to determine the appropriate clinical applications and scope of this promising technique in cardiac tumor imaging. MRI-PET fusion imaging is also common in neurologic imaging but rarely performed for cardiac imaging because of challenges in image registration. It has been shown that, at least in some cases, showing the extent of cardiac tumoral involvement can help with
patient management [60]. The clinical uses of this new technology to further characterize cardiac mass lesions and cost-benefit ratio need further investigation [61]. Conclusion Cardiac MRI is an important imaging modality for assessment of cardiac tumors because it enables noninvasive tissue characterization of tumors and determination of the extent of involvement and impact on cardiac flow and function. Familiarity with the characteristic MRI features of primary cardiac neoplasms and masslike conditions is essential for proper diagnosis and management. References 1. Holley DG, Martin GR, Brenner JI, et al. Diagnosis and management of fetal cardiac tumors: a multicenter experience and review of published reports. J Am Coll Cardiol 1995; 26:516–520 2. Beroukhim RS, Prakash A, Buechel ER, et al. Characterization of cardiac tumors in children by cardiovascular magnetic resonance imaging: a multicenter experience. J Am Coll Cardiol 2011; 58:1044–1054 3. Isaacs H Jr. Fetal and neonatal cardiac tumors. Pediatr Cardiol 2004; 25:252–273 4. Simcha A, Wells BG, Tynan MJ, Waterston DJ. Primary cardiac tumours in childhood. Arch Dis Child 1971; 46:508–514 5. Uzun O, Wilson DG, Vujanic GM, Parsons JM, De Giovanni JV. Cardiac tumours in children. Orphanet J Rare Dis 2007; 2:11 6. Chan HS, Sonley MJ, Moes CA, Daneman A, Smith CR, Martin DJ. Primary and secondary tu-
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Ghadimi Mahani et al. mors of childhood involving the heart, pericardium, and great vessels: a report of 75 cases and review of the literature. Cancer 1985; 56:825–836 7. McAllister HA Jr. Primary tumors of the heart and pericardium. Pathol Annu 1979; 14:325–355 8. Grebenc ML, Rosado de Christenson ML, Burke AP, Green CE, Galvin JR. Primary cardiac and pericardial neoplasms: radiologic-pathologic correlation. RadioGraphics 2000; 20:1073–1103; quiz, 1110–1112 9. Nir A, Tajik AJ, Freeman WK, et al. Tuberous sclerosis and cardiac rhabdomyoma. Am J Cardiol 1995; 76:419–421 10. Rienmüller R, Lloret JL, Tiling R, et al. MR imaging of pediatric cardiac tumors previously diagnosed by echocardiography. J Comput Assist Tomogr 1989; 13:621–626 11. Berkenblit R, Spindola-Franco H, Frater RW, Fish BB, Glickstein JS. MRI in the evaluation and management of a newborn infant with cardiac rhabdomyoma. Ann Thorac Surg 1997; 63:1475– 1477 12. Soler-Soler J, Romero-Gonzalez R. Calcified intramural fibroma of the left ventricle. Eur J Cardiol 1975; 3:71–73 13. Vidaillet HJ Jr. Cardiac tumors associated with hereditary syndromes. Am J Cardiol 1988; 61:1355 14. Yang HS, Arabia FA, Chaliki HP, De Petris G, Khandheria BK, Chandrasekaran K. Images in cardiovascular medicine: left atrial fibroma in Gardner syndrome—real-time 3-dimensional transesophageal echo imaging. Circulation 2008; 118:e692–e696 15. O’Donnell DH, Abbara S, Chaithiraphan V, et al. Cardiac tumors: optimal cardiac MR sequences and spectrum of imaging appearances. AJR 2009; 193:377–387 16. Kiaffas MG, Powell AJ, Geva T. Magnetic resonance imaging evaluation of cardiac tumor characteristics in infants and children. Am J Cardiol 2002; 89:1229–1233 17. Ali SZ, Susin M, Kahn E, Hajdu SI. Intracardiac teratoma in a child simulating an atrioventricular nodal tumor. Pediatr Pathol 1994; 14:913–917 18. Becker AE. Primary heart tumors in the pediatric age group: a review of salient pathologic features relevant for clinicians. Pediatr Cardiol 2000; 21:317–323 19. Aldousany AW, Joyner JC, Price RA, Boulden T, Watson D, DiSessa TG. Diagnosis and treatment of intrapericardial teratoma. Pediatr Cardiol 1987; 8:51–53 20. Seguin JR, Coulon P, Huret C, Grolleau-Roux R, Chaptal PA. Intrapericardial teratoma in infancy: a rare disease. J Cardiovasc Surg (Torino) 1986; 27:509–511 21. Molina JE, Edwards JE, Ward HB. Primary car-
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diac tumors: experience at the University of Minnesota. Thorac Cardiovasc Surg 1990; 38(suppl 2):183–191 22. Sparrow PJ, Kurian JB, Jones TR, Sivananthan MU. MR imaging of cardiac tumors. RadioGraphics 2005; 25:1255–1276 23. Arciniegas E, Hakimi M, Farooki ZQ, Truccone NJ, Green EW. Primary cardiac tumors in children. J Thorac Cardiovasc Surg 1980; 79:582–591 24. Reynen K. Cardiac myxomas. N Engl J Med 1995; 333:1610–1617 25. Bulkley BH, Hutchins GM. Atrial myxomas: a fifty year review. Am Heart J 1979; 97:639–643 26. Tazelaar HD, Locke TJ, McGregor CG. Pathology of surgically excised primary cardiac tumors. Mayo Clin Proc 1992; 67:957–965 27. McCarthy PM, Piehler JM, Schaff HV, et al. The significance of multiple, recurrent, and “complex” cardiac myxomas. J Thorac Cardiovasc Surg 1986; 91:389–396 28. Cartagena AM, Levin TL, Issenberg H, Goldman HS. Pericardial effusion and cardiac hemangioma in the neonate. Pediatr Radiol 1993; 23:384–385 29. Burke A, Johns JP, Virmani R. Hemangiomas of the heart: a clinicopathologic study of ten cases. Am J Cardiovasc Pathol 1990; 3:283–290 30. Brizard C, Latremouille C, Jebara VA, et al. Cardiac hemangiomas. Ann Thorac Surg 1993; 56:390–394 31. Lo LJ, Nucho RC, Allen JW, Rohde RL, Lau FY. Left atrial cardiac hemangioma associated with shortness of breath and palpitations. Ann Thorac Surg 2002; 73:979–981 32. Palmer TE, Tresch DD, Bonchek LI. Spontaneous resolution of a large, cavernous hemangioma of the heart. Am J Cardiol 1986; 58:184–185 33. Hananouchi GI, Goff WB 2nd. Cardiac lipoma: six-year follow-up with MRI characteristics, and a review of the literature. Magn Reson Imaging 1990; 8:825–828 34. Beghetti M, Gow RM, Haney I, Mawson J, Williams WG, Freedom RM. Pediatric primary benign cardiac tumors: a 15-year review. Am Heart J 1997; 134:1107–1114 35. Zingas AP, Carrera JD, Murray CA 3rd, Kling GA. Lipoma of the myocardium. J Comput Assist Tomogr 1983; 7:1098–1100 36. Conces DJ Jr, Vix VA, Tarver RD. Diagnosis of a myocardial lipoma by using CT. AJR 1989; 153:725–726 37. Kearney DL, Titus JL, Hawkins EP, Ott DA, Garson A Jr. Pathologic features of myocardial hamartomas causing childhood tachyarrhythmias. Circulation 1987; 75:705–710 38. Malhotra V, Ferrans VJ, Virmani R. Infantile histiocytoid cardiomyopathy: three cases and literature review. Am Heart J 1994; 128:1009–1021 39. Keller BB, Mehta AV, Shamszadeh M, et al. On-
cocytic cardiomyopathy of infancy with WolffParkinson-White syndrome and ectopic foci causing tachydysrhythmias in children. Am Heart J 1987; 114:782–792 40. Franciosi RA, Singh A. Oncocytic cardiomyopathy syndrome. Hum Pathol 1988; 19:1361–1362 41. Silver MM, Burns JE, Sethi RK, Rowe RD. Oncocytic cardiomyopathy in an infant with oncocytosis in exocrine and endocrine glands. Hum Pathol 1980; 11:598–605 42. Edwards FH, Hale D, Cohen A, Thompson L, Pezzella AT, Virmani R. Primary cardiac valve tumors. Ann Thorac Surg 1991; 52:1127–1131 43. Randhawa K, Ganeshan A, Hoey ET. Magnetic resonance imaging of cardiac tumors. Part 2. Malignant tumors and tumor-like conditions. Curr Probl Diagn Radiol 2011; 40:169–179 44. Feigin DS, Fenoglio JJ, McAllister HA, Madewell JE. Pericardial cysts: a radiologic-pathologic correlation and review. Radiology 1977; 125:15–20 45. Best AK, Dobson RL, Ahmad AR. Best cases from the AFIP: cardiac angiosarcoma. RadioGraphics 2003; 23(spec no):S141–S145 46. Chiles C, Woodard PK, Gutierrez FR, Link KM. Metastatic involvement of the heart and pericardium: CT and MR imaging. RadioGraphics 2001; 21:439–449 47. Ceresoli GL, Ferreri AJ, Bucci E, Ripa C, Ponzoni M, Villa E. Primary cardiac lymphoma in immunocompetent patients: diagnostic and therapeutic management. Cancer 1997; 80:1497–1506 48. Tada H, Asazuma K, Ohya E, et al. Images in cardiovascular medicine: primary cardiac B-cell lymphoma. Circulation 1998; 97:220–221 49. Dorsay TA, Ho VB, Rovira MJ, Armstrong MA, Brissette MD. Primary cardiac lymphoma: CT and MR findings. J Comput Assist Tomogr 1993; 17:978–981 50. Celermajer DS, Sholler GF, Howman-Giles R, Celermajer JM. Myocardial infarction in childhood: clinical analysis of 17 cases and medium term follow up of survivors. Br Heart J 1991; 65:332–336 51. Suryawanshi SP, Das B, Patnaik AN. Myocardial infarction in children: two interesting cases. Ann Pediatr Cardiol 2011; 4:81–83 52. Paydarfar D, Krieger D, Dib N, et al. In vivo magnetic resonance imaging and surgical histopathology of intracardiac masses: distinct features of subacute thrombi. Cardiology 2001; 95:40–47 53. Srichai MB, Junor C, Rodriguez LL, et al. Clinical, imaging, and pathological characteristics of left ventricular thrombus: a comparison of contrast-enhanced magnetic resonance imaging, transthoracic echocardiography, and transesophageal echocardiography with surgical or pathological validation. Am Heart J 2006;
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F O R YO U R I N F O R M AT I O N
A data supplement for this article can be viewed in the online version of the article at: www.ajronline.org.
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FOCUS ON:
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Pediatric Imaging Review
Maryam Ghadimi Mahani1 Jimmy C. Lu2 Cynthia K. Rigsby 3 Rajesh Krishnamurthy4 Adam L. Dorfman2 Prachi P. Agarwal1 Ghadimi Mahani M, Lu JC, Rigsby CK, Krishnamurthy R, Dorfman AL, Agarwal PP
Keywords: cardiac MRI, pediatric cardiac tumor DOI:10.2214/AJR.13.10680 Received February 1, 2013; accepted after revision October 13, 2013. 1 Department of Radiology, C. S. Mott Children’s Hospital, 1540 E Hospital Dr, SPC 4252, Ann Arbor, MI 48109-4252. Address correspondence to M. Ghadimi Mahani ([email protected]). 2 Department of Pediatrics, Division of Cardiology, C. S. Mott Children’s Hospital, Ann Arbor, MI. 3 Department of Medical Imaging, Ann and Robert H. Lurie Children’s Hospital of Chicago, Chicago, IL. 4 Departments of Radiology and Pediatrics, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX.
Supplemental Data Available online at www.ajronline.org. AJR 2014; 202:971–981 0361–803X/14/2025–971 © American Roentgen Ray Society
MRI of Pediatric Cardiac Masses OBJECTIVE. The purpose of this article is to describe the characteristic cardiac MRI features of primary and secondary cardiac tumors, including differentiation from masslike lesions, such as thrombus or focal myocardial hypertrophy. CONCLUSION. The frequency and type of cardiac tumors in children differ from those in adults. Although transthoracic echocardiography is the initial imaging technique of choice for evaluation of cardiac tumors, cardiac MRI is an important complementary modality for characterization of the mass and effect on cardiac function.
C
ardiac tumors are rare, with a reported prevalence range of 0.0017–0.28% in autopsy series for all ages [1, 2]. The frequency and type of cardiac tumors in children differ from adults. The prevalence of pediatric primary cardiac tumors has been reported as 0.08% in infants and children under 5 years old by one institute during a 20-year interval [2–4]; the incidence of cardiac tumors detected by fetal echocardiography has been reported as 0.14% [1]. Pediatric cardiac tumors are being diagnosed more frequently with increased use of noninvasive imaging modalities, such as fetal echocardiography and MRI. Although cardiac tumors are rare, familiarity with the imaging appearance is important to distinguish cardiac neoplasms from other common masses, such as thrombi. Furthermore, despite the varied histologic types, cardiac MRI has been shown to be predictive of the tumor type on the basis of imaging characteristics [2]. Among pediatric cardiac neoplasms, secondary tumors are more common than primary tumors. Most primary pediatric cardiac tumors are benign, with only about 10% malignant [5]. Cardiac tumors can be asymptomatic and discovered incidentally during fetal anatomic imaging, by ultrasound, or during fetal MRI. When symptomatic, tumors can present in fetal life with hydrops, congestive heart failure, arrhythmia, and even stillbirth or in postnatal life with decreased cardiac output (due to ventricular inflow or outflow obstruction), cyanosis, murmur, myocardial dysfunction,
respiratory distress, valvular insufficiency, arrhythmia, thromboembolic events, and rarely sudden death [5]. The treatment of symptomatic cardiac tumors is surgical resection; sometimes palliative surgical debulking of the mass can be performed to relieve symptoms. The mainstay of imaging cardiac tumors is echocardiography. ECG-gated CT also enables assessment of cardiac masses, although it is generally less favored, particularly in the pediatric age group, because of concern for ionizing radiation. In addition, CT has lower temporal resolution compared with echocardiography and MRI. Cardiac MRI offers a noninvasive alternative for comprehensive cardiac assessment, including tissue characterization and evaluation of tumor size, extent, and physiologic impact [2]. Additionally, MRI provides better soft-tissue contrast resolution compared with both echocardiography and CT. Tissue sampling remains the reference standard for diagnosis but may not be necessary in all cases. This article will review the MRI protocol for comprehensive cardiac mass assessment, describe the spectrum of MRI appearances of pediatric cardiac tumors and masslike lesions, and elucidate the relevant key features that can help characterize a mass. Suggested MRI Protocol for Evaluation of the Cardiac Mass The first step in planning a cardiac MRI examination and determining the optimal imaging planes is to review any available imaging. Table 1 summarizes our institutional protocol for evaluation of pediatric cardiac masses. We
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Ghadimi Mahani et al. TABLE 1: Suggested MRI Protocol for Evaluation of Cardiac Masses at Our Institution Pulse Sequence
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Technical Parameters
Utility and Characteristics
Cine steady-state free precession imaging in multiple planes
TR/TE, 3.0/1.5; FOV, 250 × 150 mm (depending on the size of the patient); slice thickness, 6–7 mm; gap, 0 mm; flip angle, 60°; 30 phases per cardiac cycle. Various planes of acquisition can be used based on location of the lesion, such as axial, two- chamber left, two-chamber right, four-chamber, horizontal long-axis, short-axis, right ventricular outflow tract, and left ventricular outflow tract. The best plane is decided after reviewing any prior studies, such as echocardiography. If no prior studies are available, an axial stack of cine MRI is obtained, which helps decide optimal plane of imaging.
High temporal and contrast resolution and signal-to-noise ratio to assess tumor location, potential effect on function and blood flow, and mobility of the mass, in multiple planes
Double inversion-recovery T1-weighted turbo spin-echo imaging
TR/TE, 1 beat/10; flip angle, 90°; number of signals acquired, 2; slice thickness, 5 mm (based on tumor and patient size and can be decreased to 3 mm as needed); matrix, 200 × 194; FOV, 250 × 150 mm (depending on patient size); inversion time, 350 ms; black blood thickness, 10 mm
Helps in tissue characterization; better delineation of mass and relation to adjacent structures
T1-weighted imaging with SPIR fat suppression
Same as double inversion-recovery T1-weighted turbo spin-echo Helps in evaluation of fat in the lesion imaging with added fat-saturation prepulse, SPIR
T2-weighted STIR turbo spin-echo imaging
TR/TE, 2 beats/70; flip angle, 90°; FOV, 300 × 300 mm; matrix, 200 × 153; slice thickness, 6–8 mm; number of signals acquired, 1; added fat-saturation STIR
Helps in tissue characterization; evaluates presence of fat in the lesion; evaluates for presence of edema
First-pass perfusion imaging
TR/TE, 2.3/1.15; FOV, 250 × 178 mm; slice thickness, 10 mm; number of slices, 3; matrix, 96 × 69 mm; flip angle, 50°; contrast administration, 3 mL/ s using 0.1 mmol/kg IV gadolinium
Evaluates vascularity, as well as presence and pattern of lesion enhancement and helps in differentiation from thrombus
Gadolinium-enhanced double inversion-recovery T1- weighted turbo spin-echo imaging immediately after contrast injection
Usually 2–3 minutes after perfusion scanning; decrease inversion time and black blood pulse slice thickness to 5 mm, otherwise exactly the same parameters as before contrast injection
Evaluates enhancement of lesion; hyperenhancement favors vascular or malignant tumor; mild contrast enhancement is seen in 40–50% of benign tumors
Scout T1-weighted TI imaging (Look-Locker)
TR/TE, 8.1/3.0; matrix, 104 × 84; flip angle, 12°; one slice repeated Allows identification of optimal TI by visual inspection 41 times; slice thickness, 10 mm; incremental increase in TI starting from 125 ms
Late gadolinium-enhanced TR/TE, 6.1/3.0; 2D segmented inversion-recovery–prepared imaging 10 min after injection fast gradient-echo sequence with TE, 3 ms; flip angle, 25°; of contrast material, average number of slices, 8–12; slice thickness, 6–8 mm. TI is segmented double inversiondetermined using Look-Locker sequence, which is performed recovery fast spin-echo in perpendicular planes in which mass is best visualized.
For presence and pattern of enhancement, myocardial scar, and differentiation from thrombus, specifically with long inversion time (600ms)
Phase contrast imaging (optional)
Phase contrast imaging perpendicular to inflow (atrioventricular valve) or outflow tract of the ventricles (above aortic or pulmonic valves) can be performed to calculate flow volumes and regurgitation; depending on location of tumor, in-plane phase contrast imaging may be helpful to assess for increased velocity
2D fast-field echo with TR/TE, 4.6/2.8; flip angle, 12°; slice thickness, 6 mm; number of signals acquired, 3; heart phases, 40; phase contrast velocity, 150–250 cm/s
Note— SPIR = spectral presaturation with inversion-recovery.
use a cumulative dose of 0.1–0.2 mmol/kg IV of a gadolinium contrast agent. First-pass perfusion imaging is acquired dynamically during contrast injection, and, subsequently, late gadolinium-enhanced images are acquired 10 minutes after contrast injection. We use a 2D cine steady-state free precession (SSFP) sequence in appropriate imaging planes to assess for tumor size and motion with the cardiac cycle and potential impedance to flow and cardiac function (Fig. 1). Black blood imaging (T1-weighted imaging with and without fat suppression and T2-weighted imaging with fat suppression) as well as enhancement of the mass using first-pass perfusion imaging
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and delayed enhancement are used for mass characterization. When differentiation from thrombus is necessary, delayed enhancement with a long inversion time (600 ms) is preferred. Additional sequences can be used on the basis of the precise clinical question, such as 3D SSFP (particularly for assessing relationship to coronary arteries), MR angiography (MRA) for relationship to vascular structures, and flow velocity mapping for assessing impedance to blood flow. Pediatric Cardiac Tumors This article will focus mainly on primary cardiac neoplasms and their mimics. Imaging
Fig. 1—Screen capture from video of horizontal longaxis steady-state free precession cardiac video (see Fig. S1 in supplemental data online).
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Solitary or multiple, associated with tuberous sclerosis Solitary, well-defined border with thin rim of myocardium Cystic, multilobulated, pericardial effusion, tamponade, fetal hydrops
Pedunculated mobile mass with irregular border Intramural or endocardial
Usually solitary, multiple can be seen in association with other congenital heart disease Small in size; 1- to 2-mm, yellowish nodule on endocardium, epicardium, or valve Single unilocular cystic lesion
Irregular ill-defined border; pericardial or pleural involvement
Multiple, large pericardial effusion; no central necrosis Multiple lesions, large size, irregular ill-defined border; pericardial or pleural involvement
Fibroma
Teratoma
Myxoma
Hemangioma
Lipoma
Purkinje cell tumor
Pleuropericardial cyst
Rhabdomyosarcoma, symptoms associated with periradial and pleural disease and embolic phenomena
Lymphoma
Cardiac metastasis
Appearance and Characteristics
Rhabdomyoma
Tumor Type
Mostly right heart
Mostly involves right heart
Any chamber of the heart
Usually in right cardiophrenic angle; can be seen anywhere in mediastinum
Left ventricle and along conduction system
Mostly arises from epicardial surface; can involve all three layers of heart
Anywhere in heart; minimal predilection for ventricular septum and right atrium
Sporadic in left atrium, interatrial septum near fossa ovalis, familial in any chamber
Usually in pericardial cavity attached to pulmonary artery and aorta or arising from atrial or ventricular wall protruding into cardiac chamber
Intramyocardial ventricular septum or free wall
Intramyocardial or intracavitary, any chamber of the heart
Location
Heterogeneous
Homogeneous
Homogenous with occasional central necrosis
Homogeneous
Homogeneous
Heterogeneous
Heterogeneous, encapsulated, complex cystic mass
Heterogeneous
Homogeneous in all sequences
Imaging Characteristics on MRI
TABLE 2: Imaging Characteristics of Pediatric Cardiac Tumors
Hypointense
Iso- to slightly hypointense
Isointense
Hypointense; hyperintense if hemorrhagic or proteinaceous fluid
Hyperintense
Hyperintense, signal loss (hypointense) on fat-saturated sequence
Intermediate
Hypointense, hyperintense if proteinaceous
Isointense
T1-Weighted
Heterogeneous
Isointense
Hypointense
Hypointense
Hyperintense
Hypointense
Hypointense core with periphery isointense
Minimal hyperintense or variable
Contrast-Enhanced T1-Weighted
Hyperintense
Isointense
Hyperintense
Iso- or hypointense
Hyperintense
Hyperintense
Hyperintense
Mildly hyperintense
T2-Weighted
Pulse Sequence
Heterogeneous
Variable, minimal uptake
Hypointense
Hypointense
Variable, iso- to mildly hyperintense
Heterogeneous, variable
Hyperintense with or without dark center (hypointense)
Isointense
Late GadoliniumEnhanced
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MRI of Pediatric Cardiac Masses
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Primary Benign Pediatric Cardiac Tumors Most primary cardiac tumors are benign in children. These include rhabdomyoma, fibroma, teratoma, myxoma, hemangioma, and other rare tumors, with rhabdomyoma the most common [6, 7]. Rhabdomyoma—The most common benign pediatric cardiac tumor is rhabdomyoma, a hamartoma of the myocardium. It is frequently associated with tuberous sclerosis; half of the patients with rhabdomyomas also have tuberous sclerosis [8]. Partial or complete regression occurs in fetal life and in children less than 4 years old [1, 8, 9]. This fact coupled with a better survival of tuberous sclerosis patients without rhabdomyomas explains the decreased prevalence of this tumor with advancing age. Rhabdomyoma can be asymptomatic or may present with outflow tract obstruction, arrhythmia, and heart failure. In fetal life, presentation may be with hydrops fetalis or stillbirth. If asymptomatic, treatment is not needed because most tumors typically regress. If intervention is necessary, for instance in patients with left ventricular outflow tract obstruction or arrhythmia, the prognosis is good after excision. Rhabdomyomas are either intramyocardial or intracavitary and attached to the myocardium. On cardiac MRI, rhabdomyomas (Fig. 2) [2] are homogeneous on all sequences, mildly hyperintense on T2-weighted imaging, isointense to myocardium on T1weighted sequences, and show minimal or no
enhancement after administration of gadolinium-based contrast agents with hypointensity on first-pass perfusion imaging and isointensity on late gadolinium-enhanced sequences. Cardiac MRI and echocardiography are complementary modalities for diagnosing rhabdomyomas. Some rhabdomyomas detected with ultrasound may be missed with MRI, especially small (< 0.5 cm) or completely intramural lesions. However, MRI is superior to echocardiography in detecting intracavitary tumors and delineation of the extracardiac extension of the tumors [10]. MRI assessment of rhabdomyomas and other cardiac tumors is particularly helpful when surgical resection is being considered [11] because the anatomy and location of the mass or masses with respect to adjacent vital structures in the heart can be better evaluated with cardiac MRI. Fibroma—Cardiac fibroma is the second most common cardiac tumor in children and is typically located in the ventricular septum. These masses are derived from connective tissue fibroblasts and may invade the functional ventricular myocardium, resulting in congestive heart failure. They may also invade the conducting system and cause arrhythmia or even sudden cardiac death. Unlike rhabdomyomas, cardiac fibromas rarely regress, and surgery is often indicated. Partial resection may be the only option in patients with a widespread tumor that is not fully resectable [5, 8] (Fig. 3). Calcification within the center of the mass reflects poor blood supply and is considered pathognomonic for fibroma [5, 12]. Calcification is seen in 50% of pathologic specimens;
however, the radiographic evidence of tumor calcification is seen in 25% of cases [8] (Fig. 3). On CT, the tumor is seen as a heterogeneous mural mass with areas of calcification. Although cardiac fibroma usually occurs in isolation, there is increased risk of cardiac fibroma in patients with Gorlin syndrome (basal cell nevus syndrome, which is characterized by multiple nevoid basal cell carcinomas of skin, mandibular cysts, and bifid ribs) [13]. Cardiac fibroma also has a rare association with familial adenomatous polyposis and its subtype Gardner syndrome [14, 15]. The characteristic features of cardiac fibromas have been described as follows [2] (Fig. 3): usually solitary intramyocardial mass with well-defined borders involving the ventricular septum or free wall with a heterogeneous appearance and variable areas of mildly hypo- or hyperintense signal on T1-weighted and T2weighted sequences, hypointense on first-pass perfusion imaging, and hyperenhancement on late gadolinium-enhanced sequences with or without a hypoenhancing (dark) center. On MRA, fibromas have also been described to have a strongly hypointense core with isointense shell at the periphery [2, 16]. Fibromas associated with familial polyposis syndrome have also been seen in atria [15]. Areas of calcification can be seen as signal voids on MRI; however, in general, MRI is less sensitive compared with CT in detecting areas of calcification. Teratoma—Cardiac teratoma is an extremely rare tumor in the pediatric population [17]. It is usually extracardiac, located in the pericardium, and attached to the root
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characteristics of cardiac masses on specific pulse sequences are summarized in Table 2.
Fig. 2—Rhabdomyoma in 1-day-old boy with prenatal diagnosis of cardiac tumor. A–C, Cardiac MR images show that mass (arrow) arises from lateral wall of left ventricle and is isointense to myocardium on T1-weighted images without fat saturation before (not shown) and after contrast administration (A), mildly hyperintense on T2-weighted fat-saturated image (B), and isointense on late gadolinium-enhanced image (C). Patient remained asymptomatic. These features are most consistent with rhabdomyoma.
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MRI of Pediatric Cardiac Masses Fig. 3—Cardiac fibroma in 13-month-old girl under workup for prominent heart murmur. A, After abnormal echocardiogram that showed large heterogeneous probably calcified mass compressing right ventricular outflow tract, frontal chest radiograph obtained before cardiac MRI shows heterogeneous calcification in region of ventricle (arrow). B–D, Patient underwent cardiac MRI for further evaluation, which revealed large mass (arrows) involving right ventricular outflow tract and free wall of right ventricle. Mass has well-defined border and is mainly isointense to hypointense on T1-weighted sequence (B) and heterogeneous and mainly hyperintense with hypointense areas on T2weighted sequence with fat saturation (C). Mass is in close relationship to right coronary artery, and 3D steady-state free precession image (D) shows right coronary artery in right atrioventricular groove directly over mass. E, Late gadolinium-enhanced image shows peripheral late gadolinium enhancement (black arrow), with dark core of hypoenhancement (white arrow).
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of the aorta and pulmonary trunk. It rarely involves the myocardium, presenting as an intracardiac mass arising from the atrial or ventricular wall [18] (Fig. 4). Pericardial teratoma is easily detected by fetal echocardiography as a heterogeneous and encapsulated cystic mass, typically positioned on the right side of the heart [8]. Associated pericardial effusion is frequent [19, 20]. Teratomas involving the anterior mediastinum may grow rapidly. Chest radiography may reveal an enlarged cardiomediastinal silhouette and rarely may show calcification or formed teeth [8]. Macroscopically, teratomas have cystic and solid components with a multilocular appearance (Fig. 5). Microscopically, teratomas contain elements derived from all three germ layers. The main clinical findings result from mass effect of the tumor on the heart and
Fig. 4—Intramyocardial teratoma in 10-day-old girl with tachypnea, harsh murmur, and cardiomegaly. A and B, Cardiac MR images obtained after abnormal echocardiogram show multicystic mass invading entire interventricular septum (arrow, A) on short-axis steady-state free precession image (A). First-pass perfusion image (B) shows septal mass of decreased signal intensity without significant perfusion (arrows, B).
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Ghadimi Mahani et al. from the associated pericardial effusion. Fetal hydrops and stillbirth have been reported [5]. Surgical total or partial resection of teratoma has a favorable outcome [21]. The characteristic features include multilocular mass with cystic and solid components usually in intrapericardial location compressing the superior vena cava or right atrium (Fig. 5). They show heterogeneous signal intensity on T1-weighted and T2weighted sequences with areas of high signal intensity on T2-weighted imaging and hypointensity on first-pass perfusion imaging. Myxoma—Although myxoma is the most common primary benign tumor in adults, typically presenting between the fourth and seventh decades [22], it rarely occurs in children [23]. Myxoma can occur sporadically or may be seen in association with syndromes. The sporadic forms are more common in females [24] and in the left atrium, although myxoma can also occur in the right atrium [25] or in the ventricles. There is a predilection for the interatrial septum, in a region near the fossa ovalis [26] (Fig. 6). A small percentage (7%) of myxomas are syndromic. In these cases, tumors are multifocal, seen in chambers of the heart other than the left atrium, have a higher recurrence rate after surgical resection, and are more often seen in males and at younger ages. There may also be a familial predisposition for cardiac myxoma [27]. Clinical presentations of cardiac myxoma include breathlessness, syncope, embolism, congestive heart failure, arrhythmia, and constitutional symptoms. Right-sided myxomas are rare and can cause pulmonary embolism, tricuspid and pulmonary artery ob-
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Fig. 5—Pericardial teratoma in 13-year-old boy. A and B, Pericardial teratoma presenting as large multicystic tumor (arrows) appears mildly hyperintense on echo-planar T1-weighted image (A) due to proteinaceous-mucinous content, hyperintense on T2-weighted owing sequence (not shown), and with eccentric enhancement of solid component along medial aspect of tumor along with enhancement of septa on gadolinium-enhanced coronal echo-planar T1-weighted image (B). There is extrinsic mass effect on lateral wall of right atrium and cavoatrial junction.
struction, and right-heart failure [5]. Because the presenting symptoms can be nonspecific, myxomas may be clinically unsuspected and diagnosed late. Surgical resection has a favorable outcome with minimal or no recurrence. The characteristic features include pedunculated mobile mass with irregular borders commonly arising from the leftward aspect of the interatrial septum, hyperintensity on T2-weighted sequences (Fig. 6), heterogeneous enhancement with predominantly hypointensity on first-pass perfusion sequences, and iso- to hyperintense areas on late gadolinium-enhanced sequences. Hemangioma—Hemangiomas are rare benign vascular tumors that affect all age
groups [8, 22] and can be located anywhere in the heart, with a minimal predilection for the ventricular septum and right atrium [5]. Hemangiomas may be intramural or endocardial and can present as subendocardial nodules in the size range of 2–4 cm [28]. Cardiac hemangiomas are microscopically classified as cavernous, capillary, and arteriovenous. Clinically, hemangiomas are usually asymptomatic but can present with ventricular tachycardia, high-output cardiac failure, hemorrhage, pericardial effusion, cardiac tamponade, or thrombocytopenia [5]. Cardiac hemangiomas can be associated with hemangiomas in other sites, such as bowel, oral cavity, or skin [29].
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Fig. 6—Myxoma in 13-year-old boy. A–C, Cardiac MR images show myxoma as pedunculated oval-shaped mass (arrows) arising from interatrial septum and protruding superior to septal leaflet of mitral valve. Mass appears hyperintense on T2-weighted image (A), isointense to myocardium on echo-planar T1-weighted image (B), and with hyperintense rim enhancement on contrast-enhanced echo-planar T1-weighted image (C). RA = right atrium, RV = right ventricle, LV = left ventricle, LA = left atrium, VS = ventricular septum, AS = atrial septum, AO = aortic root.
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MRI of Pediatric Cardiac Masses Differentiation of hemangiomas from malignant vascular tumors may not be possible by MRI unless frank signs of invasion or metastases are seen [2]. Cardiac hemangiomas respond well to surgical excision if clinically necessary, such as when associated with obstructive symptoms [29–31]. Surgery is not necessary for asymptomatic hemangiomas because spontaneous regression has been reported [32]. The characteristic features include intermediate signal on T1-weighted and hyperintense signal on T2-weighted sequences, avid enhancement on first-pass perfusion sequences (Fig. 7) (a feature that will differentiate these from teratomas), and isointense or mildly hyperintense on late gadoliniumenhanced sequences. Lipoma—Lipomas have been reported in a wide age range of patients [33, 34] but are more common in adults. Most lesions arise from the epicardial surface; however, they can involve all three layers of the heart, including myocardium and endocardium [8, 22, 35]. Lipomas are usually solitary, but multiple lipomas have been reported in conjunction with congenital heart diseases, tuberous sclerosis, or sometimes sporadically in otherwise normal hearts [35, 36]. The characteristic features include homogeneous high signal intensity on T1weighted sequences, mildly hyperintense on T2-weighted sequences, loss of signal on fat suppression sequences, and no enhancement on first-pass perfusion sequences. Purkinje cell tumor—Purkinje cell tumor is considered a cardiac hamartoma [37] and has been described only in infants and children. It is distinct from rhabdomyoma and is known by different names, including foamy myocardial transformation of infancy, infantile xanthomatous cardiomyopathy, infantile cardiomyopathy with histiocytoid change, and histiocytoid cardiomyopathy in infancy [18]. Morphologically, it consists of focal collections of altered myocytes that are round and similar to histiocytes. Macroscopically, the tumor presents as yellowish nodules on the endocardium, epicardium, or valves ranging between 1–2 mm in size [38], with a propensity for the left ventricle and the conduction system [5]. Refractory arrhythmia is the most common clinical presentation [5, 39]. There are some reports of association with congenital heart disease, such as hypoplastic heart syndrome and atrial and ventricular septal defects [40], and with extracardiac anomalies [41].
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Fig. 7—13-year-old girl with septal mass noted on echocardiogram. A–D, Cardiac MR images show hemangioma (arrow), which is heterogeneous mass in ventricular septum mainly isointense to hypointense on axial T1-weighted image (A) and hyperintense on T2-weighted image with fat saturation (B), with enhancement on contrast-enhanced image (not shown). Septal mass (hemangioma) is hyperintense on T1-weighted late gadolinium-enhanced image (C) and shows strong enhancement on firstpass perfusion image (D).
The characteristic features include hyperintensity on T1-weighted sequences, isointensity to hypointensity on T2-weighted sequences, and no significant enhancement on first-pass perfusion sequences [2]. Other Benign Cardiac Tumors Papillary fibroelastomas—Papillary fibroelastomas are benign endocardial papillomas that predominantly affect the cardiac valves at a mean age of 60 years [42]. These tumors are very rare in children and manifest as pedunculated or mobile masses arising from endocardial cavity or valve on imaging [2]. Pleuropericardial cysts—Pleuropericardial cysts are benign congenital cystic lesions that arise from the pericardium but do not communicate with the pericardial space. They are most commonly found at the right cardiophrenic angle, but approximately one third of them can be found anywhere in the mediastinum. They are
usually unilocular simple cystic lesions with low signal intensity on T1-weighted sequences and high signal intensity on T2-weighted sequences with no enhancement on first-pass perfusion or contrast-enhanced sequences. Occasionally they contain proteinaceous material and have high signal intensity on both T1- and T2-weighted sequences [22, 43, 44]. Patients are usually asymptomatic, but approximately one third may complain of chest pain, dyspnea, or persistent cough [44]. Malignant Cardiac Tumors Malignant cardiac tumors are very rare in children and constitute a small proportion of cardiac masses, with 95% sarcomas (Fig. 8) and the rest lymphomas [5]. Cardiac sarcoma has several histologic subtypes, including angiosarcoma, rhabdomyosarcoma, malignant fibrous histiocytoma, undifferentiated sarcoma, and fibrosarcoma [45].
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Ghadimi Mahani et al. Secondary involvement of the heart by extracardiac primary malignancies is much more common than primary malignant cardiac tumors (Fig. 9). In the pediatric age group, metastases can be secondary to leukemia, lymphoma, Wilms tumor, hepatoblastoma, neuroblastoma, Ewing sarcoma, and osteosarcoma. Malignancies can involve the heart by lymphatic extension, hematogenous spread, or direct contiguous extension, or it can be spread via large vessels, such as the inferior vena cava [46]. The characteristic features of malignant cardiac tumors include heterogeneous signal intensity on all MRI sequences; infiltrative appearance crossing an annular or tissue plane within the heart or involving both cardiac and extracardiac structures, for example, extension to the mediastinum and great vessels; history of extracardiac malignancy (often present); arising from the right atrium; hemorrhagic pericardial effusion, and large size (more than 5 cm). It should be noted that none of the cardiac MRI features are very sensitive or specific for the diagnosis of the malignant cardiac masses [43]. Rhabdomyosarcoma—Rhabdomyosarcoma is the most common primary cardiac malignancy of childhood. There are two histologic subtypes of rhabdomyosarcoma: embryonal type, which is more common, and pleomorphic type, which is less frequent and mainly occurs in adults. There is no pre-
Fig. 9—Metastatic medulloblastoma in 12-year-old girl with known primary tumor in brain. Four-chamber gadolinium-enhanced echo-planar image shows heterogeneous enhancement of mass (arrow). Mass is centered on inferior atrial septum extending into crux of heart, encasing aortic annulus and septal leaflets of tricuspid and mitral valves, causing obstruction to atrioventricular valve inflow and aortic outflow. RA = right atrium, RV = right ventricle, LV = left ventricle, LA = left atrium, VS = ventricular septum, AS = atrial septum, AO = aortic root.
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Fig. 8—Primary cardiac sarcoma in 8-year-old boy. Axial T1-weighted image with fat saturation after IV administration of gadoliniumbased contrast agent shows infiltrating poorly defined mass (white arrow) centered on posterior atrial wall, with extension into pericardial cavity and heterogeneous enhancement. Associated malignant effusion of pericardium is also present with abnormal enhancement (black arrow). Small right pleural effusion is also seen (asterisk). RA = right atrium, RV = right ventricle, LV = left ventricle, LA = left atrium,
dilection for any specific cardiac chamber, although it more often involves the cardiac valves compared with other sarcomas and has a tendency to be multicentric [22, 43]. The characteristic features include a large infiltrative mass with irregular margin and central necrosis or cavitation, isointensity on T1-weighted sequences, hyperintensity in the center of the mass on T2-weighted sequences, heterogeneous enhancement on T1-weighted contrast-enhanced sequences because of central necrosis and cavitation, and peripheral hyperintensity on late gadolinium-enhanced sequences [22]. Primary cardiac lymphoma—Primary cardiac lymphoma is typically non-Hodgkin B cell type and is more common in adults and immunocompromised patients, with a mean age of 60 years and reported age range of 13–90 years [43]. Cardiac lymphoma is multicentric in 75% of cases and commonly involves the right side of the heart, especially the right atrium followed by the right ventricle, left ventricle, left atrium, atrial septum, and ventricular septum. There can be invasion of the pericardium, with possible massive pericardial effusion [8, 47]. The characteristic features include isointense to slightly hypointense on T1-weighted sequences, isointense on T2-weighted sequences, and minimal enhancement after gadolinium administration with areas of relatively lower enhancement in the center compared with the periphery [48, 49]. Nonneoplastic Cardiac Masses and Masslike Lesions Several cardiac lesions can mimic neoplasms on imaging. MRI can help facilitate differentiation and direct management.
Cardiac thrombus—Cardiac thrombus is by far the most common cardiac mass. Thrombi can occur in any cardiac chamber and are seen in the left atrial appendage in the setting of atrial fibrillation, in the right atrium in the presence of a central venous catheter, and in the ventricles (particularly the left) with aneurysmal dilatation after acute myocardial infarction. Although it should be noted that myocardial infarction is very rare in children, it can occur in some groups of children, for example, in anomalous origin of the left coronary artery, Kawasaki disease, idiopathic or congenital cardiomyopathies, nephrotic syndrome, and as a complication of surgical repair of congenital heart disease [50, 51]. The typical imaging appearance of a thrombus is that of a hypointense nonenhancing mass. The precise MRI characteristics depend on the age of the thrombus. Subacute thrombi are homogeneously low in signal intensity on gradient-echo sequences and do not enhance after gadolinium administration. However, organized chronic thrombi can be heterogeneous with intermediate signal intensity on gradient-echo sequences and with areas of enhancement after administration of contrast material, especially at the periphery because of the presence of vascular channels [52]. Differentiation of a cardiac thrombus from tumors, such as myxoma, can be difficult on echocardiography. Both lesions can occur in the left atrium and may be associated with atrial fibrillation. Low signal intensity and nonenhancement after gadolinium administration are useful clues that favor thrombus, although sometimes differentiation can be difficult. Late gadolinium-enhanced sequenc-
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MRI of Pediatric Cardiac Masses
Fig. 10—Short-axis late gadolinium-enhanced image in 12-year-old boy with osteosarcoma and right atrial thrombosis. Late gadolinium-enhanced cardiac MR image, which was obtained to evaluate right atrial mass seen on echocardiogram (not shown), shows lack of enhancement of thrombus (arrow).
es with a long inversion time (600 ms) can null the avascular tissue and have been found to be useful and sensitive for diagnosing thrombus. Thrombus will remain low in signal intensity, and myocardium and tumor may show an increase in signal intensity [53, 54]. The characteristic features include nonenhancing hypointense lesions on first-pass perfusion sequences, hypointensity on late gadolinium-enhanced sequences (Fig. 10), and hypointensity relative to the myocardium on late gadolinium-enhanced sequences with a long inversion time of 600 ms. Hypertrophic cardiomyopathy—Hypertrophic cardiomyopathy (HCM) is a myocardial disorder characterized by left ventricular hypertrophy in the absence of causes such as pressure overload or storage-infiltrative disease. The pathognomonic histologic features are myocyte disarray and fibrosis [55, 56]. HCM has a spectrum of manifestations, both clinically and morphologically. Clinical presentation ranges from asymptomatic to sudden cardiac death. Different morphologic imaging subtypes of HCM have been described in the literature, for example, asymmetric HCM with predominant involvement of the basal septum, HCM with midventricular obstruction (with or without a left ventricular apical diverticulum), apical HCM, symmetric (concentric) HCM, and masslike HCM. Sometimes HCM may present in the burned-out stage with focal or diffuse thinning of the myocardium. Right ventricular involvement occurs in 17.6% of cases of HCM [56, 57]. In many of its morphologic subtypes, particularly in the focal mass like
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Fig. 11—17-year-old boy with idiopathic hypertrophic cardiomyopathy. A and B, Cardiac MR images show asymmetric masslike thickening of inferior interventricular septum and areas of hyperenhancement on late gadolinium-enhanced image (arrow, A) in short-axis plane. Note decreased contraction in area of hypertrophied myocardium compared with adjacent normal myocardium revealed by decreased distortion of tagging (arrows, B) compared with adjacent normal myocardium during systole.
type of HCM, the disorder can mimic a cardiac tumor (Fig. 11). MRI can help in differentiation of focal HCM from a true mass. The signal intensity of focal HCM follows that of the adjacent myocardium on the black blood and cine images with midmyocardial patchy areas of enhancement on late gadolinium-enhanced sequences. In contrast, cardiac tumors can be recognized by their characteristic appearance on MRI as detailed earlier. Additional sequences, such as myocardial tagging, can show decreased contractility compared with adjacent myocardium in the area of focal HCM with fibrosis; however, cardiac masses typically do not show any contractility. Further investigation to define the sensitivity and specificity of this application of cardiac MRI is still needed [58]. Future Directions in Cardiac Tumor Imaging Diffusion-weighted MRI (DWI) has been widely used in whole-body tumor imaging, but its utility in cardiac imaging is limited because of signal loss from cardiac motion. Recently, DWI has been used to differentiate pericardial cysts from other solid tumors [59]. However, further research is required to determine the appropriate clinical applications and scope of this promising technique in cardiac tumor imaging. MRI-PET fusion imaging is also common in neurologic imaging but rarely performed for cardiac imaging because of challenges in image registration. It has been shown that, at least in some cases, showing the extent of cardiac tumoral involvement can help with
patient management [60]. The clinical uses of this new technology to further characterize cardiac mass lesions and cost-benefit ratio need further investigation [61]. Conclusion Cardiac MRI is an important imaging modality for assessment of cardiac tumors because it enables noninvasive tissue characterization of tumors and determination of the extent of involvement and impact on cardiac flow and function. Familiarity with the characteristic MRI features of primary cardiac neoplasms and masslike conditions is essential for proper diagnosis and management. References 1. Holley DG, Martin GR, Brenner JI, et al. Diagnosis and management of fetal cardiac tumors: a multicenter experience and review of published reports. J Am Coll Cardiol 1995; 26:516–520 2. Beroukhim RS, Prakash A, Buechel ER, et al. Characterization of cardiac tumors in children by cardiovascular magnetic resonance imaging: a multicenter experience. J Am Coll Cardiol 2011; 58:1044–1054 3. Isaacs H Jr. Fetal and neonatal cardiac tumors. Pediatr Cardiol 2004; 25:252–273 4. Simcha A, Wells BG, Tynan MJ, Waterston DJ. Primary cardiac tumours in childhood. Arch Dis Child 1971; 46:508–514 5. Uzun O, Wilson DG, Vujanic GM, Parsons JM, De Giovanni JV. Cardiac tumours in children. Orphanet J Rare Dis 2007; 2:11 6. Chan HS, Sonley MJ, Moes CA, Daneman A, Smith CR, Martin DJ. Primary and secondary tu-
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