Eur Radiol DOI 10.1007/s00330-014-3585-z

CARDIAC

Characteristics of aortic valve dysfunction and ascending aorta dimensions according to bicuspid aortic valve morphology Hong Ju Shin & Je Kyoun Shin & Hyun Kun Chee & Jun Suk Kim & Sung Min Ko

Received: 10 June 2014 / Revised: 19 November 2014 / Accepted: 22 December 2014 # European Society of Radiology 2015

Abstract Objective To characterize aortic valve dysfunction and ascending aorta dimensions according to bicuspid aortic valve (BAV) morphology using computed tomography (CT) and surgical findings. Methods We retrospectively enrolled 209 patients with BAVs who underwent transthoracic echocardiography (TTE) and CT. BAVs were classified as anterior-posterior (BAV-AP) or lateral (BAV-LA) orientation of the cusps and divided according to the presence (raphe+) or absence (raphe–) of a raphe. Ascending aortic dimensions were measured by CT at four levels. Results BAV-AP was present in 129 patients (61.7 %) and raphe+ in 120 (57.4 %). Sixty-nine patients (33.0 %) had aortic regurgitation (AR), 70 (33.5 %) had aortic stenosis (AS), and 58 (27.8 %) had combined AS and AR. AR was more common in patients with BAV-AP and raphe+; AS was more common with BAV-LA and raphe–.Annulus/body surface area and tubular portion/body surface area diameters in patients with BAV-AP (17.1±2.3 mm/m2 and 24.2±5.3 mm/m2, respectively) and raphe+ (17.3±2.2 mm/m2 and 24.2±5.5 mm/m2, respectively) were significantly different from those with BAV-LA (15.8± 1.9 mm/m2 and 26.4±5.5 mm/m2, respectively) and raphe– (15.7±1.9 mm/m2 and 26.2±5.4 mm/m2, respectively).

Conclusion The morphological characteristics of BAV might be associated with the type of valvular dysfunction, and degree and location of an ascending aorta dilatation. Key points • The BAV-AP type had more frequent aortic regurgitation, raphe, and a larger aortic annulus. • BAV without raphe had more frequent aortic stenosis and mid-ascending aorta dilatation. • CT allows assessment of the morphological characteristics of BAV and associated aortopathy. Keywords Computed tomography . Transthoracic echocardiography . Bicuspid aortic valve . Aortic stenosis . Aortic regurgitation

H. J. Shin : J. K. Shin : H. K. Chee : J. S. Kim Department of Cardiovascular Surgery, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Korea

Abbreviations AA Ascending aorta AR Aortic regurgitation AS Aortic stenosis ASR Aortic stenosis and regurgitation BAV Bicuspid aortic valve BPM Beats per minute CCTA Coronary computed tomography angiography CT Computed tomography ECG Electrocardiography HR Heart rate MDCT Multidetector computed tomography TAV Tricuspid aortic valve TTE Transthoracic echocardiography

S. M. Ko (*) Department of Radiology, Konkuk University Medical Center, Konkuk University School of Medicine, 4-12 Hwayang-dong, Gwangjin-gu, Seoul 143-729, Korea e-mail: [email protected]

Introduction

H. J. Shin Department of Cardiovascular Surgery, Yonsei University College of Medicine, Seoul, Korea

A bicuspid aortic valve (BAV) is the most common congenital cardiac malformation, affecting 0.5–2 % of the general

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population. Patients with a BAV have an increased risk for serious valvular lesions, including aortic stenosis (AS), aortic regurgitation (AR), and infective endocarditis, as well as aortic wall abnormalities such as ascending aorta dilatation, aneurysm, and dissection [1]. BAVs have various phenotypes according to the presence and orientation of cusps and raphes. The morphological features of a BAV may affect valve dysfunction and aortic elastic properties [2, 3]. Therefore, patients with a BAV need a careful assessment of the morphological patterns, valve-related complications, ascending aorta dimensions, and the rate of increase in the ascending aorta dimension to determine an appropriate surveillance and treatment plan. Transthoracic echocardiography (TTE) is the standard diagnostic tool for identifying the morphologic features of BAVs and assessing valvular dysfunction and aortic root diameters. However, findings of a prominent raphe, extensively calcified valve cusps, poor acoustic windows, and technical limitations prohibit adequately visualizing the cusp, leading to misdiagnosis as tricuspid aortic valve (TAV) disease [4]. In addition, TTE has difficulty obtaining an adequate view of the mid and distal ascending aorta and aortic arch [5]. Transesophageal echocardiography (TEE) is very accurate at detecting BAVs and coexisting cardiovascular malformations. However, it is a semi-invasive procedure and is not free of risk. Retrospective electrocardiography (ECG)-gated multidetector computed tomography (MDCT) provides morphological information and functional cine imaging of the aortic valve. Cardiac MDCT is an accurate imaging modality for discriminating between a BAV and a TAV [4, 6–9]. Compared with aortic valve surgical findings, sensitivity, specificity, and positive and negative predictive values for differentiating TAVs and non-TAVs are 97 %, 95 %, 98 %, and 94 % with MDCT in 262 patients and 98 %, 88 %, 95 %, and 96 % with TTE in 249 patients [8]. In particular, MDCT provides clues about differentiating between the raphe in BAVs and degenerative commissural fusion in TAVs compared with surgical findings in patients with severe valvular calcification [9]. In addition, detailed and accurate information on the ascending aorta dimensions provided by MDCT may be valuable for decision-making concerning simultaneous repair of a dilated ascending aorta in patients with a BAV [5, 10]. Evaluation of the association between BAV morphology and the pattern of aortic valve dysfunction or ascending aorta dimensions is currently performed mostly with TTE [2, 3, 11]; MDCT data are lacking in the literature [12]. Therefore, we characterized aortic valve dysfunction and ascending aorta dimensions according to BAV morphology in a larger number of patients with a BAV using dual-source CT and surgical findings.

Methods Patient population Our institutional review board approved this retrospective study and informed consent was exempted. A computerized search of medical and radiological records from October 2007 to November 2012 identified 209 patients (152 men; mean age, 51.7 ±14.4 years) with a BAV who underwent both TTE and cardiac CT evaluation at our institution. One hundred eighty-four patients underwent aortic valve surgery in the inclusion period. However, 15 patients who underwent aortic valve surgery did not undergo cardiac CT (TTE only) because of combined severe aortic valvular dysfunction and severe left ventricular dysfunction. In 169 patients (80.9 %), BAV diagnosis was made upon surgery and, in the remaining 40 patients who were not treated surgically, the diagnosis was made via cardiac CT. Cardiac CT was performed as the preoperative coronary artery anatomy evaluation, determining the aortic valve morphology, the presence and extent of aortic valve cusp calcification, and ascending aorta dimensions. Baseline clinical characteristics, results of cardiac evaluations, and detailed surgery information were determined from the medical and radiological records.

CT imaging protocol All CT examinations were performed using a dual-source CT scanner (Somatom Definition, Siemens Medical Solutions, Forchheim, Germany). Prior to the examination, the heart rate (HR) of each patient was measured. Patients with a pre-scan HR >65 beats per min (bpm) and without contraindications for using beta-blockers were given 50–100 mg of metoprolol orally 1 hr prior to coronary CT angiography (CCTA). All patients received 0.6 mg of nitroglycerin sublingually 1 min before the examination. Calcium scoring started 2 cm below the carina to just below the diaphragm. CCTA was performed from 2 cm above the carina to the diaphragm without including the entire aortic arch. Data acquisition was performed in a craniocaudal direction with a detector collimation of 2×32×0.6 mm, a slice acquisition of 2 × 64 × 0.6 mm, a gantry rotation time of 330 ms, a pitch of 0.20–0.43 adapted to HR, a tube voltages of 120 kV for the calcium score and 100 or 120 kV for CCTA (depending on patient age and body mass index), and a tube current-time product of 80 mAs per rotation for calcium scoring and 330 mAs per rotation for CCTA. A non-enhanced ECG-gated CT, prospectively triggered at 75 % of the R-R interval, was performed to measure the coronary artery and aortic valve calcium score. ECG-based tube current modulation was implemented for CCTA, except for patients with mean HRs >80 bpm or those with arrhythmia. The full dose

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window of 20–70 % of the cardiac cycle was used in patients with a HR ≤80 bpm. Contrast agent application was controlled by a bolus tracking technique. A Stellant D dual-head power injector (Medrad, Indianola, PA, USA) was used for all CT examinations to administer a three-phase bolus at a rate of 4.5 mL/s. First, 70–80 mL of undiluted contrast media (Iopromide, Ultravist 370 mg I/mL, Bayer-Schering Pharma, Berlin, Germany) was administered after optimal timing was determined using a bolus tracking technique. Forty-five cc of a mixture of 70 % contrast and 30 % saline was administered with a saline chaser for CCTA. CT image reconstruction and analysis Ten transaxial datasets were reconstructed with retrospective ECG gating at 10 % steps, from 0 to 90 % of the R-R interval for each patient to assess BAV morphology and function. CCTA images were reconstructed with a slice thickness of 1.0 mm, and the reconstruction increment was set to 0.5 mm. Images were reconstructed with a section thickness of 3 mm and a reconstruction internment of 1.5 mm to quantify the coronary artery and aortic valve calcium score, such as the Agatston score. CCTA datasets reconstructed every 10 % of the cardiac cycle were then transferred to an external workstation (Vitrea 2, Vital Images, Plymouth, MN, USA) and reviewed by applying multiplanar reformations and a fourdimensional cine technique. Post-processing included both Fig. 1 Bicuspid aortic valve (BAV) classification. BAV-AP is defined as an anterior-posterior orientation of the cusps (a) or raphe (b, arrow). BAV-LA is defined as a right-left orientation of the cusps (c) or raphe (d, arrow). BAV phenotype is divided according to presence (b, d) or absence (a, c) of a raphe

static and cine images of the aortic valve in double-oblique short-axis planes. Several cross-sectional transverse images of the aortic valve during early-systole and mid-diastole were reconstructed for the morphologic and functional aspects of the BAV in a craniocaudal direction ranging from the top of the cusps to the infundibulum. Regurgitant orifice area and stenotic aortic valve area were measured using CT planimetry at mid-diastole and early systole, respectively. Double-oblique coronal images of the ascending aorta were reconstructed at 10 % or 20 % of the cardiac cycle (early to mid-systole) to measure the ascending aorta dimensions. All CT images were analyzed by a consensus of two radiologists. The presence of a BAV was confirmed with visualization of two cusps and commissures with or without a raphe in both systole and diastole. BAV morphology was classified into anterior-posterior orientation of cusps (BAV-AP) and lateral orientation of cusps (BAV-LA) by the orientation of the free edge [12] and divided into the presence of raphe (raphe+) or the absence of raphe (raphe–) (Fig. 1). We measured the ascending aorta dimensions manually with electronic calipers at the following four different levels: level 1, the aortic annulus, defined as the hinge points of the aortic valve cusps; level 2, the mid-point of the aortic sinus of Valsalva; level 3, the sinotubular junction; and level 4, the tubular portion of the ascending aorta at the level of the maximal dimension. The ascending aorta was assigned to one of four main anatomical types according to the segment of the vessel exclusively or

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predominantly involved in dilatation, as follows: (1) normal aorta; (2) mid-ascending consisting of dilatation at the tubular ascending portion (with normal sinuses or markedly lower dimensions at the root level; ascending aorta >4 cm); (3) dilated root (flask-like dilatation, isolated or prevailing at the sinusal portion, sinus of Valsalva diameter >4 cm); and (4) combined dilated root and mid-ascending type (diameter of root and ascending aorta >4 cm) [12] (Fig. 2).

Echocardiographic evaluation Aortic valve morphology and the presence and severity of AS/ AR were recorded by cardiologists from the patient’s electronic medical records. Two-dimensional TTE was performed with a Vivid 7 device (GE Healthcare; Wauwatosa, WI, USA) and an Acuson Sequoia C512 apparatus (Siemens, Erlangen, Germany) with 2.5–3.5 MHz imaging transducers. AS/AR severity was determined to be mild, moderate, or severe by including some or all of the following parameters according to American College of Cardiology/American Heart Association guidelines [13]. A proximal regurgitation jet width of 65 % of LVOT as severe AR. A vena contracta length of 0.6 cm as severe AR. Using the pressure half-time technique, a pressure half-time of >500 ms was considered mild AR, 200–500 ms as moderate AR, and 1.5 cm2 was taken as mild AS, 1.0–1.5 cm 2 as moderate AS, and 1.0 cm2 mmHg as severe AS.

Operation A total of 169 patients (80.9 %) underwent open-heart surgery with aortic valvuloplasty (n=158 (93.5 %), our specific approach, differing from other institutions [14], and aortic valve replacement (n=11, 6.5 %). From the operative records, we reviewed the presence or absence of a raphe, the spatial cusp positions, the relative cusp sizes, the extent of valve calcification, and the location of the dilated ascending aorta. Seventy-

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three patients underwent concomitant ascending aorta wrapping (n=66) or graft replacement (n=7). Patients who had valvular dysfunction symptoms that were AS or AR greater than mild underwent surgery. Operation was also performed when ascending aorta dilation was >45 mm, even if the valvular dysfunction was mild. Calcification of the aortic valve was observed in most of the patients with dominant AS. After excising the aortic valve, we examined the commissure from the ventricular side and distinguished BAVs from severe calcified TAVs, which are similar to BAVs. Statistical analyses Continuous variables are presented as mean ± standard deviation (SD) or median and range depending on the normality of their distribution. Categorical variables are summarized as frequencies and percentages. Patient characteristics according to the morphologic BAV subtype were compared using the chi-square test or Fisher’s exact test for categorical variables and the two-sample ttest for continuous variables. Kappa statistics were used to determine intermodality diagnostic agreement. This analysis was performed with SAS 9.2 software (SAS Institute, Cary, NC, USA). All reported P-values are two sided; a P-value

Characteristics of aortic valve dysfunction and ascending aorta dimensions according to bicuspid aortic valve morphology.

To characterize aortic valve dysfunction and ascending aorta dimensions according to bicuspid aortic valve (BAV) morphology using computed tomography ...
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