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Ann Thorac Surg 2000;70:119-123
© 2000 The Society of Thoracic Surgeons

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Original articles: Cardiovascular

Coronary to pulmonary artery collaterals in patients with pulmonary atresia and ventricular septal defect

^a Department of Pediatrics, University of California, San Francisco, San Francisco, California, USA
^b Department of Surgery, University of California, San Francisco, San Francisco, California, USA

Address reprint requests to Dr Amin, Joint Division of Pediatric Cardiology, UN/CU, Children’s Hospital, 8301 Dodge St, Omaha, NE 68114
e-mail: zamin{at}pcard.unmc.edu

	Abstract

Top Abstract Introduction Patients and methods Results Comment References

 
Background. The frequency, distribution, and surgical importance of coronary artery to pulmonary artery (CAPA) collaterals have not been established. The aim of this study was to establish prevalence, anatomical pattern, and significance of CAPA in patients with pulmonary atresia and ventricular septal defect (PA/VSD).

Methods. We reviewed cardiac catheterization and operative data of 87 consecutive, unselected patients who underwent one-stage complete unifocalization for PA/VSD and assessed major systemic to pulmonary collaterals from July 1992 to June 1998.

Results. CAPA collaterals were diagnosed in 9 of 87 patients (10%). The collaterals originated from the left coronary artery system in 7 patients and the right in 2. Collaterals from the left coronary system arose from the left main coronary artery in 3 patients and the circumflex in 4. All collaterals joined the central pulmonary artery, which bifurcated and supplied both lungs. One collateral from the right coronary system joined the stump of the main pulmonary artery and the other gave origin to a true left pulmonary artery, which was the sole supply to 75% of the left lung. Coronary artery enlargement was seen in 2 patients only. No patient had evidence of myocardial ischemia. Coronary collaterals comprised a dual source of pulmonary blood flow in all but 1 patient. During unifocalization, the CAPA collaterals were ligated at its origin in all cases, and the collateral from the right coronary to the left pulmonary artery was unifocalized.

Conclusions. The prevalence of CAPA collaterals in patients with PA/VSD is approximately 10%. The diagnosis may be missed without appropriate angiograms. We recommend selective ascending aortogram or selective coronary angiogram in all patients.

	Introduction

Top Abstract Introduction Patients and methods Results Comment References

 
Pulmonary atresia with ventricular septal defect and major systemic to pulmonary arterial collaterals is a complex congenital heart lesion with an incidence of 4.2 per 100,000 live births [1]. Pulmonary blood flow in these patients may arise from different segments of the aorta or its branches. The majority of collaterals originate from the descending thoracic aorta at the level of carina, the lower descending thoracic and abdominal aorta, and the subclavian artery and its branches [2, 3]. Occasionally, collaterals may arise from the left or right coronary artery [3]. Although a number of cases of coronary artery to pulmonary artery (CAPA) collaterals have been reported in patients with pulmonary atresia and ventricular septal defect [3–13], the incidence, anatomy, distribution patterns, and surgical significance of CAPA have not been established.

Since 1992, our approach to the management of pulmonary atresia with ventricular septal defect and systemic to pulmonary collaterals (SPCAs) has focused on one stage complete unifocalization of pulmonary blood supply early in life [2, 14]. With the development of this management program, preoperative cardiac catheterization is critical, and is carried out with an emphasis on identifying and characterizing all sources of pulmonary arterial blood supply. This aggressive approach allows for observations regarding the incidence and anatomical patterns of CAPA in this group of patients. In this report, we describe our experience with CAPA in patients with pulmonary atresia and ventricular septal defect.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment References

 
From July 1992 to June 1998, 87 consecutive, unselected patients underwent unifocalization procedures for pulmonary atresia with ventricular septal defect and SPCAs. The median age at repair was 7 months (10 days to 37 years). All patients had preoperative cardiac catheterization performed at our institution.

The nature of blood supply (unifocal or dual) to all lung segments was established at the time of catheterization by angiography. All preoperative catheterization data and angiograms were reviewed for this study in order to identify CAPA. Cardiac catheterization was performed through the femoral vein and artery. After obtaining hemodynamic measurements, a high descending aortogram was performed with a pigtail catheter passed retrograde through the femoral artery. In our earlier experience, which included a total of 15 patients, an ascending aortogram was obtained in patients in whom there was the suspicion of a CAPA on the initial high descending aortogram. We now perform an ascending aortogram in all patients. Selective angiograms were performed in the innominate and subclavian arteries if collateral vessels could not be excluded by the central aortic angiogarms. After all SPCAs were delineated, a coaxial catheter system, consisting of a Transit (Cordis Corp, Miami, FL) catheter placed through a Glide catheter (Terumo Corp, Tokyo, Japan) was used to enter the collaterals individually for measurement of distal pressures. Selective angiograms were then obtained at the origin of the collaterals using the Glidecath. The coronary arteries were not entered routinely, even if a CAPA was identified. In the 1 patient in whom the majority of pulmonary blood flow arose from a dilated right coronary artery, the pulmonary artery was entered through the CAPA to obtain pressure data and an angiogram. Electrocardiograms were reviewed to evaluate for ischemic changes. Since patients with this diagnosis invariably undergo catheterization, extensive efforts to delineate the collateral arteries by echocardiography were not made. Operative records were reviewed to determine the specific technique of unifocalization and the management of CAPA in these patients.

	Results

Top Abstract Introduction Patients and methods Results Comment References

 
Among the overall cohort of 87 patients who had cardiac catheterization prior to unifocalization, 9 were found to have CAPA. Seven of the 9 patients were infants (median age 9 months). The number of total collaterals in these patients (median 4, range 3 to 5) was the same as in patients without CAPA. All patients had true central pulmonary arteries, which were confluent in all but 1. The origin and supply of CAPA varied considerably. Seven CAPA arose from the left coronary system, 3 from the left main coronary artery, and 4 from the circumflex, while 2 arose from the right coronary system. All CAPA from the left coronary system ranged from small (< 2 mm) to medium (< 4 mm) in size, and joined the central pulmonary artery to supply both lung fields (Fig 1). One of the CAPA from the right coronary joined the stump of the main pulmonary artery just proximal to the bifurcation and served as a dual source of supply to 70% of lung segments. The other gave origin to the true left pulmonary artery (Fig 2) and was the sole blood supply to 75% of the left lung. Mild distal coronary artery enlargement was seen in 2 patients, both of who had CAPA originating from the left coronary artery system.

View larger version (72K): [in this window] [in a new window]   Fig 1. Left coronary angiography demonstrating CAPA collateral from the left main coronary to central pulmonary artery in anterior posterior (A) and lateral (B) view.

View larger version (81K): [in this window] [in a new window]   Fig 2. Ascending aortogram in left anterior oblique (A) and lateral (B) view. CAPA from the right coronary artery, which gave origin to the true left pulmonary artery, is seen.

All CAPA from the left coronary artery system and the CAPA from the right coronary artery to main pulmonary artery were ligated, because these vessels constituted a dual source of blood to the involved lung segments. The CAPA that served as the sole supply of blood flow to the left lung was unifocalized. There was no operative mortality, and 8 of the 9 patients were alive at most recent follow-up (5 to 61 months postoperatively). The remaining patient died following conduit replacement 49 months after the unifocalization procedure.

	Comment

Top Abstract Introduction Patients and methods Results Comment References

 
SPCAs are thought to represent remnants of the splanchnic vascular system supplying the primordial lung beds, which are derived from the embryonic foregut [15]. These vessels normally regress with the formation of the normal pulmonary arterial system later in development. However, they may persist when there is early maldevelopment of the central pulmonary arterial system, derived from the truncus arteriosus, aortic sac, and proximal segments of the sixth aortic arches, as occurs in pulmonary atresia and ventricular septal defect (PA/VSD). The central pulmonary arterial system does not develop proper continuity with the embryonic lung, and consequently a normal pulmonary arterial tree is not formed. At the same time, SPCAs predominate and create a vast array of arterial connections to various lung segments. These SPCA may be true bronchial arteries, which run along the airway and arise primarily from the descending thoracic aorta, or other primitive vessels that arise from the brachiocephalic vessels or thoracic and abdominal segments of the descending aorta. On the other hand, pulmonary blood flow in patients with PA/VSD may also have vessels that communicate with the true central pulmonary arterial system. A ductus arteriosus is an example of such a vessel. Similarly, the coronary arteries may communicate with the arch-derived central pulmonary arteries both in otherwise normal anatomy (eg, coronary to pulmonary artery fistula [16]) and in pulmonary atresia with ventricular septal defect. Although CAPA may provide sole supply to the pulmonary arterial system, typically they do not, presumably because they are either too small to conduct enough blood or the connections occur at too late an embryological stage. Thus, although CAPA are generally categorized as SPCAs in the setting of pulmonary atresia with ventricular septal defect, we hypothesize that they are physiologically and embryologically more similar to a ductus arteriosus than to SPCAs. CAPA join the central arch-derived pulmonary arteries in an antegrade fashion, as is the case with a ductus arteriosus but not with SPCA, which generally are not in continuity with the true pulmonary arteries, and typically make connections within the lung parenchyma or at the hilum when they are. Clear definition of this system may be associated with better surgical outcome and fewer subsequent interventions [17], because a reconstituted central system tends to grow better and faster if composed of true central pulmonary arteries. Therefore, a clear definition of CAPA will help in defining the true central pulmonary arterial system.

Since 1992, our approach to PA/VSD and SPCA has been complete unifocalization of the pulmonary blood supply through a midline one-stage approach. The emphasis has been on repair in early infancy using native tissue to tissue reconstruction. A one-stage repair has been possible in 93% of our patients, with early [2] and midterm [14] results that have been encouraging. In order to optimize the use of native tissue in the unifocalization and to ensure that as many lung segments as possible are supplied by the unifocalized neopulmonary artery system, it is imperative that every collateral vessel is accounted for prior to surgery. Thus, in all of our patients, a standard aggressive approach to cardiac catheterization is employed. An attempt is made to enter every collateral vessel to measure pressures and perform an angiogram to ascertain the nature of blood supply to all lung segments. This strategy has allowed complete detection of all patients with CAPA.

Prevalence of coronary to pulmonary artery collaterals
In this retrospective study of cardiac catheterization data and operative reports, we found a prevalence of 10% at the time of preoperative catheterization in a population of 87 consecutive patients with PA/VSD and SPCAs. Although CAPA have been reported in approximately 23 patients prior to this [3–13], a true prevalence cannot be derived from these reports, because the population of patients with pulmonary atresia were neither reported nor rigorously screened for CAPA. Hofbeck and colleagues [13], in a review of 32 patients with pulmonary atresia and ventricular septal defect, reported 1 with CAPA. This retrospective study spanned a 14-year period. Almost 88% percent of the patients underwent cardiac catheterization, but it was not evident whether ascending aortograms were performed. Liao and associates [3] reviewed 31 autopsy cases seen over a period of 8 years and found 2 patients (7%) with CAPA. Dabizzi and colleagues [18] reported 11% of their patients with tetralogy of Fallot to have small fistulous connections between the coronary and pulmonary artery systems. Pahl and coworkers [5] described 4 patients with CAPA over a 33-year period, but no mention was made of the total number of patients with pulmonary atresia. One of their patients developed pulmonary hypertension thought to be secondary to increased flow through the CAPA, which reinforces the need for a thorough diagnostic cardiac catheterization. They recommended that CAPA should be considered as a possible source of pulmonary blood flow in all patients with pulmonary atresia and ventricular septal defect. Most other reports of CAPA have been simply case reports.

Anatomical patterns
CAPA can arise from either the left or right coronary systems and take a variety of forms. Of the 9 patients with CAPA in our experience, the CAPA arose from the left coronary system in 7 and from the right in 2. This is similar to the distribution of previously reported CAPA, of which a large majority has originated from the left coronary artery system. Among our 9 patients, the CAPA was a redundant source of flow to confluent central pulmonary arteries in 8. In the remaining patient, 75% of the left lung was supplied by the CAPA, which originated from the right coronary system. It is interesting to note that all patients with CAPA in our experience have had a favorable anatomy for one-stage unifocalization, insofar as they all had confluent central pulmonary arteries. In this respect, our patients are characteristic of the cumulative reported experience, as all CAPA described in previous reports have connected with the true pulmonary arteries centrally, usually constituting dual supply to one or both lungs, but sometimes providing sole supply from only a few segments to as much as both lungs. Compared with our entire population of patients with PA/VSD and SPCAs, those with CAPA were not found to differ in terms of the total number or anatomy of the non-CAPA collaterals. In previous reports, most patients have had additional SPCAs, but the number and distribution of these have not been described.

Clinical implications
The physiological importance of CAPA in patients with pulmonary atresia and ventricular septal defect has not been well defined. There have been no reported cases of ischemia in patients with CAPA, even in those who survive into adulthood. Vigneswaran and Pollock [10] reported a 41-year-old patient who had CAPA but no history of chest pain, electrocardiographic changes indicative of ischemia, or myocardial infarction. Although, at first glance, coronary steal by the pulmonary bed may seem likely with CAPA, coronary perfusion should be independent of the pulmonary bed, dependent only on the distal coronary bed as long as the proximal coronary is widely patent without limitation to flow. In fact, all of our patients with CAPA had either normal or enlarged proximal coronaries on the involved side, which has been a common finding in previously reported cases as well. From the perspective of the distal coronary bed, the physiology of this condition is no different than a patient with a large patent ductus arteriosus, a Blalock-Taussig shunt, or SPCA. It is not surprising then that the presence of CAPA in our patients did not influence the preoperative presentation.

From an operative point of view, the implications of CAPA appear to be minor as long as they are well-delineated preoperatively. CAPA can and should be treated as any other collateral artery. That is, the collateral should be ligated prior to the institution of cardiopulmonary bypass and incorporated into the unifocalization if it does not constitute redundant supply or can facilitate native tissue-to-tissue reconstruction. In our experience, CAPA were a redundant source of pulmonary blood flow with little independent tissue in all but 1 patient, so they were ligated. We encountered no complications or difficulties specific to CAPA in these 9 patients, and postoperative outcome did not differ between these patients and those without CAPA. However, the small number of patients confounds comparison between patients with and without CAPA.

The most significant clinical implication of CAPA is the need for accurate preoperative recognition in order to ensure that the connections can be dealt with appropriately at surgery. For a one-stage unifocalization procedure, appropriate surgical management will range from ligation of the CAPA if dual supply is present to incorporation of the proximal vessel into the unifocalization of the central pulmonary arteries. Krongrad and coworkers [4] suggested that an aortic root injection be performed for better definition of the collaterals in patients in whom CAPA are suspected. We concur with this suggestion and recommend that an ascending aortogram or selective coronary arteriogram be performed in all patients with pulmonary atresia, ventricular septal defect, and SPCA, to ensure that these important vessels are not overlooked. In addition, we recommend selective injections in the innominate, carotid, and subclavian arteries because of the significant incidence of isolated large collaterals originating from these vessels.

Study limitation
The first 15 patients did not have an ascending aortogram, and therefore we may have missed CAPA in some of the patients. However, all of these patients have had repeat cardiac catheterization and none were found to have CAPA.

	References

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