Coronary-pulmonary artery fistula in tetralogy of Fallot with pulmonary atresia
Asian Cardiovascular & Thoracic Annals 2014, Vol. 22(8) 1003–1009 ß The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0218492313505101 aan.sagepub.com
Sachin Talwar1, Robert H Anderson2, Vikas Kumar Keshri1, Shiv Kumar Choudhary1, Gurpreet Singh Gulati1 and Balram Airan1
Abstract Surgical correction of patients with tetralogy of Fallot with pulmonary atresia is now one of the routine procedures performed by pediatric cardiac surgeons. In one variant, the pulmonary arterial supply is derived from a fistulous communication from the coronary arteries. This rare and interesting situation poses a diagnostic and therapeutic dilemma, as well as providing specific management challenges to the surgical team. Here, we discuss important aspects of this rare variant, specifically its morphology, presentation, evaluation and management.
Keywords Arterio-arterial fistula, heart defects, congenital, fistula, pulmonary atresia, tetralogy of Fallot
Introduction Tetralogy of Fallot with pulmonary atresia is deﬁned as no direct continuity between the cavities of the right ventricle and the pulmonary trunk. Of necessity in such circumstances, there must be alternative sources of ﬂow of blood to the lungs. In most instances, the ﬂow is through a persistently patent arterial duct or large systemicto-pulmonary collateral arteries. Much less frequently, the supply is derived via an aortopulmonary window or ﬁstulous communication from the coronary arteries.1–5 The latter arrangement was ﬁrst reported in 1950 by Allanby and colleagues6 from Guy’s Hospital in London. Subsequently, there have been several accounts of ﬁstulous communications as the predominant source of pulmonary arterial supply.7–13 Dabizzi and colleagues,4 perhaps surprisingly, argued that one-tenth of their large series of patients studied angiocardiographically had such ﬁstulous communications from the coronary arteries, but all the identiﬁed ﬁstulas were small. The presence of such collateral channels nonetheless has important clinical and surgical implications.
Sources of pulmonary blood flow in tetralogy of Fallot with pulmonary atresia A persistently patent arterial duct is the major source of arterial ﬂow to the lungs in approximately
two-thirds of cases.1,2 In most other patients, the major source is through collateral arteries, most of which arise from the descending thoracic aorta.1 The collateral arteries can also arise from the abdominal aorta or one of its branches, the subclavian vessels, or the coronary arteries. Other rare sources of collateral supply include aortopulmonary windows and persistence of the evanescent artery of the ﬁfth aortic arch.1,6 It is very rare for major collateral arteries to supply a lung that was initially fed through a persistently patent arterial duct.1–3,15–17 We are aware of less than 40 patients reported in the English medical literature in whom ﬁstulous communication from the coronary arteries have provided the predominant or a signiﬁcant source of pulmonary arterial supply.7–9,12,18 In physiological and hemodynamic terms, ﬁstulous communications from the coronary
1 Cardiothoracic Centre, All India Institute of Medical Sciences, New Delhi, India 2 Institute of Genetic Medicine, Newcastle upon Tyne, UK
Corresponding author: Sachin Talwar, MCh, Department of Cardiothoracic and Vascular Surgery, All India Institute of Medical Sciences, New Delhi 110029, India. Email: [email protected]
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arteries are more likely to supply through the arterial duct than the more usual systemic-to-pulmonary collateral arteries. The ﬁstulous communications typically supply the entirety of intrapericardial pulmonary arterial bed, feeding the arteries in antegrade fashion, as does the arterial duct. The systemic-to-pulmonary collateral arteries in contrast either do not make any connections with the intrapericardial pulmonary arteries or else feed the pulmonary arteries within the lung parenchyma or at the hilum.
Morphology Blood supply via ﬁstulous communications from the coronary arteries exists either when the ﬁstula is the solitary or predominant source of supply,8,9 or when it exists along with additional sources of pulmonary ﬂow.18 Among the reported cases of patients with predominant arterial supply through ﬁstulous communications, only three-ﬁfths had additional associated major collateral arteries.19 The ﬁstulous communication itself can arise from either the left or right coronary artery. Among the cases we reviewed, three-quarters had the ﬁstula arising from the left coronary artery.7–9,12,18 In a few cases, the ﬁstula was described as arising from a solitary coronary artery, most commonly the left, which then supplied both coronary arterial systems.7,9 In most cases involving the left coronary arterial system, the ﬁstula arose from the anterior interventricular artery, followed by the main stem of the left coronary artery, and less frequently from the circumﬂex artery.9,18 When the right coronary arterial system has been involved, the ﬁstula was always described as arising from its proximal segment. Most frequently, the ﬁstula itself terminates in the pulmonary trunk, typically after taking a varying tortuous course. More rarely, the ﬁstula itself can give rise to major systemic-to-pulmonary collateral arteries that then extend into the pulmonary parenchyma, rather than supplying the lungs through the intrapericardial pulmonary arteries.18,19 This is an important distinction because the latter type of collateral arteries can regress spontaneously.7 In most instances, the intrapericardial pulmonary arteries are conﬂuent and of good size, although rarely, they may be hypoplastic. It is almost certainly the presence of antegrade ﬂow that permits growth of the intrapericardial pulmonary arteries despite pulmonary atresia.7 The pattern of ﬂow in the intrapericardial pulmonary arteries in these cases is similar to the duct-dependent ﬂow seen in the majority of patients with tetralogy of Fallot and pulmonary atresia.22 In all cases, the coronary artery giving rise to the ﬁstula is dilated proximally (Figure 1).13 The distal course of the coronary artery giving rise to the ﬁstula is otherwise normal in terms of caliber, ﬂow and function.8,9
Figure 1. An angiogram obtained by injecting the main stem of the left coronary artery, shown in left lateral view, reveals the dilated main stem (LMCA) and its proximal anterior interventricular branch (LAD) proximal to the site of the fistulous communication, with the pulmonary arteries filling through the fistula. The circumflex artery and LAD distal to the site of the fistulous communication are of normal calibre.8
Hemodynamic and physiologic effects In all cases reported to date, the coronary artery proximal to the site of the ﬁstula has been enlarged, supplying blood to both the pulmonary and coronary arteries.8 This leads to transmission of unrestricted systemic pressures to both distal beds. Thus the coronary arterial ﬂow is not dependent on the pulmonary ﬂow. Rather, it is more dependent on ﬂow to the distal coronary arterial bed. Because of this, there is no coronary steal phenomenon, and as far as we are aware, no reported instances of myocardial ischemia. Because these patients have signiﬁcant ﬂow into their pulmonary arteries, they usually have minimal or mild cyanosis, along with relatively well-developed and conﬂuent intrapericardial pulmonary arteries.18 If untreated, long-standing hypoxemia and their inability to increase the ﬂow of blood to the lungs during exercise, eventually results in dyspnea. The size of the communication between the coronary artery and the pulmonary arteries is typically restrictive, and hence there is only mildto-moderate elevation of pulmonary arterial pressures.9 The theoretical risk of development of pulmonary vascular disease cannot be excluded. Indeed, we are aware of at least 3 patients with features of pulmonary arterial hypertension.7,8,20 Of these 3 patients, 2 were in their fourth to ﬁfth decade of life,8,20 and the other was found to be inoperable at the age of 7 years due to severe pulmonary arterial hypertension.10 In the overall group of patients, ﬂow to the lungs is dependent on the size of the pulmonary arteries and their capacity to accommodate the ﬂow. In patients with hypoplastic and restrictive pulmonary arteries the pulmonary ﬂow is therefore reduced.12 It is important to identify such
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Figure 2. (a) Volume-rendered reconstruction of a computed tomogram showing confluent pulmonary arteries of good size, and the pulmonary end of the fistula (*). (b) An axial thick multiplanar reconstruction revealing the fistula originating from the anterior interventricular coronary artery (*). Ao: aorta; PA: pulmonary trunk.8
situations as early as possible, even if there are other potential sources of pulmonary ﬂow.
Clinical presentation and diagnosis Age at presentation can vary from early infancy to late adulthood.20,22 The mode of clinical presentation is no less variable. The presenting features range from asymptomatic patients to those exhibiting severe cyanosis, or the ﬁnding being diagnosed incidentally at the time of open heart surgery. Cyanosis is the most common presenting feature.7,22 Should there be excessive pulmonary ﬂow, then patients may present with congestive failure.22 As we have already discussed, pulmonary hypertension can develop, but this is also very rare.23 The presence of a ﬁstulous communication can be suspected after echocardiographic investigation, but diagnosis is made most often on cardiac catheterization, and conﬁrmed in the operating room. In some reported cases, the diagnosis was not established until after death. In some patients, a ﬁstula may be suspected if repeated attempts to advance a catheter into the distal pulmonary arteries result in repeated slipping of the catheter from the pulmonary trunk into a distal coronary artery. A selective root angiogram along with a selective coronary angiogram is then all that is required to conﬁrm the diagnosis. The major lesions to be excluded in the diﬀerential diagnosis are aortopulmonary window and a common arterial trunk. In the
setting of a window, there is usually pulmonary hypertension and dilation of the intrapericardial pulmonary arteries. The ﬁnding of low to normal pulmonary arterial pressures favors the presence of a ﬁstulous communication.13 In patients with a common arterial trunk, the pulmonary arteries arise directly from the trunk itself, which exits from the base of the heart through a common truncal valve.13
Evaluation and management Clinical evaluation should aim to conﬁrm the diagnosis, deﬁne the anatomy, evaluate the coronary arteries, conﬁrm the presence or absence of additional collateral arteries and their physiological signiﬁcance, and deﬁne the precise nature of the pulmonary arterial supply and the structure of the outﬂow tract from the right ventricle. To achieve these aims, a complete workup requires angiocardiography to deﬁne the cardiac anatomy and demonstrate the ﬁstula, selective root aortography to determine the anatomy of the ﬁstula for better delineation of the collateral arteries, selective coronary angiography to delineate the origin, course, and connection of the ﬁstula along with the coronary arterial distribution, and an injection into the descending thoracic aorta to conﬁrm the presence or absence of additional collateral arteries.8,9 Selective injections into the brachiocephalic, carotid, and subclavian arteries are often needed to exclude additional collateral arteries.24 For the success of one-stage correction and
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Figure 3. Multiplanar reconstructions in the coronal oblique plane, showing the aorta (Ao), pulmonary trunk (PA), fistula (*), and left anterior descending artery (arrow).
Figure 4. Volume-rendered reconstruction of the fistula (*) from the main stem of the left coronary artery to the pulmonary trunk (PA).
unifocalization, it is essential to identify the pulmonary arterial supply to all lung segments. Hence an aggressive approach to cardiac catheterization is recommended, entering each collateral vessel to measure the pressure and perform angiography. This provides a roadmap to subsequent unifocalization.24 Computed tomographic angiography is becoming increasingly important in delineating all sources of pulmonary ﬂow, and in ascertaining whether collateral arteries are providing the sole supply to the lung (Figures 2– 5). These investigations of course supplement standard echocardiography which remains the mainstay of deﬁning the intracardiac anatomy.
Surgical correction The essential goals of surgical correction are to close the ﬁstulous communication, to ensure unhindered coronary arterial ﬂow, to close the ventricular septal defect
Figure 5. Computed tomography angiogram showing the right coronary artery (*) arising from the aorta (Ao) and forming a fistulous tract that continues into the right pulmonary artery (R). The left pulmonary artery (L) is very small.
with relief of right ventricular outﬂow obstruction, and to establish unobstructed continuity between the right ventricle and the intrapericardial pulmonary arteries. Often, this may be combined with ligation or unifocalization of additional collateral arteries. Closure of the ﬁstulous communication depends on whether there is an additional source of supply to the lungs. If found, additional sources are treated by ligation and division immediately upon institution of cardiopulmonary bypass and prior to administration of cardioplegia. If providing the sole source of supply, the ﬁstula needs to be surgically unifocalized.8,18,24 This is best achieved by oversewing the ﬁstula from within the pulmonary trunk. This avoids any dissection of the coronary arteries, especially of the dilated upstream portion, and prevents injury or interruption of important branches. This approach also decreases the chances of
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Figure 6. A diagram of the patient anatomy depicted in Figures 1 and 2, showing (a) the fistula from the LAD crossing the right ventricular outflow tract, (b) the opened pulmonary trunk and the opened right ventricular outflow tract, with a gap of 1 cm between the openings crossed by the dilated LAD, and (c) direct closure of the fistula with the gap now bridged by a fresh autologous pericardial patch. CAPA: fistulous communication; LAD: anterior interventricular coronary artery.8
iatrogenic coronary arterial injury. Closure through this approach also means that the opening of the ﬁstula is readily accessible, and the approximation and closure of its margins is possible with fairly low tension on the suture line.18,23 The standard approach to a one-stage repair is through a median sternotomy, using hypothermic cardiopulmonary bypass. Upon opening the thoracic cavity, any additional collateral arteries are identiﬁed and looped. The aorta and the pulmonary trunk are separated from each other, and the intrapericardial pulmonary arteries are dissected and mobilized to the hilum of both lungs, and looped. Immediately after institution of cardiopulmonary bypass with bicaval cannulation, any additional collateral arteries are ligated. The right and left pulmonary arteries are temporarily occluded with vascular loops to prevent runoﬀ into the pulmonary circulation as well as coronary arterial steal. It is only after these maneuvers that
cardioplegia is administered. The pulmonary trunk is then opened between stays to identify the opening of the ﬁstula, and the ﬁstula is closed using a patch. The ﬁnal step is to close the ventricular septal defect and reconstruct the right ventricular outﬂow tract, following the usual protocol for any patient with tetralogy of Fallot.23 In cases where detachment of the pulmonary trunk is likely to result in kinking or damage to the coronary arteries, the posterior wall of the outﬂow tract is constructed using a pericardial patch, and the anterior portion is hooded with a homograft or pericardial patch (Figure 6). Use of a valved homograft conduit also remains an option in such cases.8
Staged vs. single-stage repair The need for staging may sometimes arise due to various presentations and variations in the anatomy of the disease. In neonates, early ligation of ﬁstula with
1008 establishment of antegrade pulmonary blood ﬂow through a systemic-to-pulmonary arterial shunt, or placement of a conduit from the right ventricle to the pulmonary arteries, are alternative options. This is followed by intracardiac repair when the child is older and gains weight.8 In such patients, if the situation demands, the procedures are staged in 3 phases. The ﬁrst involves creation of a shunt and division of the ﬁstula, preserving the native tissue. The second stage is to reconstruct the right ventricular outﬂow tract using the native tissue, along with occlusion of the prosthetic shunt. The ﬁnal stage is to close the ventricular septal defect.19 Alternatively, in children with large collateral arteries, when there may be concern about the development of obstructive pulmonary vascular disease, the ﬁrst stage may involve ligation of the collateral arteries to decrease the pulmonary blood ﬂow, followed by division of the ﬁstula, ﬁxing the stump of the pulmonary trunk to the right ventricle and creation of a systemic-to pulmonary-arterial shunt, followed by closure of the ventricular septal defect, reconstruction of the outﬂow tract, and plugging of the prosthetic shunt in the third stage.19 In most of these patients, a single-stage operation remains the preferred approach.8,24 This is reported to be possible in almost all patients, with encouraging early and midterm results.24–26 The recommended requirements for single-stage repair include a central pulmonary arterial area at least half of normal, and at least one whole lung’s worth of pulmonary segments.25 Patients who do not meet these criteria are subjected to staged repair. The advantage of a single-stage repair is that it shortens the duration over which the collateral arteries are exposed to systemic pressures, thus decreasing the chances of myointimal hyperplasia and eventual occlusion.21,26 It also prevents the development of pulmonary vascular occlusive disease in the segments supplied by the large collateral arteries or prosthetic systemic-to-pulmonary arterial shunts. In addition, the scarring and distortion of the pulmonary arteries by multiple surgical procedures and prosthetic conduits is prevented, as well as loss of recruitable lung segments.
Follow-up and outcomes As yet, there has been no reported large series with which to deﬁne the adequacy of follow-up and outcomes. However, various case reports have described a favorable outcome subsequent to surgical correction.
Funding This research received no speciﬁc grant from any funding agency in the public, commercial, or not-for-proﬁt sectors.
Asian Cardiovascular & Thoracic Annals 22(8) Conflicts of interest statement None declared.
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