Congenital Anomalies of the Coronary Arteries

Introduction

Congenital anomalies of the coronary arteries represent a varied group of lesions. Taken together, they are relatively common, seen in 1% to 5% of the population, depending on the method of detection. Many lesions are incidental findings with little or no consequences, but approximately 20% have the potential to cause coronary ischemia and its sequelae.

Box 46-1 presents a useful classification of all congenital coronary artery lesions. Some of these—an anomalous or eccentric location of a coronary artery ostium, multiple ostia, and duplication of coronary arteries—have no physiologic importance but may be important if other cardiac procedures are required. Others lesions such as myocardial bridging, ectasia or aneurysm, and small fistulas may or may not have to be surgically repaired, depending on whether or not they have physiologic consequences.

The most important lesions include large coronary arteriovenous fistula, anomalous connection of a coronary artery to the pulmonary trunk, and anomalous connection of a coronary artery to the wrong aortic sinus. All require surgical correction, or occasionally other intervention. This chapter focuses on these three lesions. A discussion of the more minor and incidental lesions outlined in Box 46-1 can be found in the review by Kayalar and colleagues.

Definition

A congenital coronary arteriovenous (AV) fistula is a direct communication between a coronary artery and the lumen of any one of the four cardiac chambers, the coronary sinus or its tributary veins, or the superior vena cava, pulmonary artery, or pulmonary veins close to the heart. Fistulous coronary connections that occur in congenital pulmonary and aortic atresia (see “Right Ventricular Coronary Artery Fistulae” under Morphology in Chapter 40 and “Other Associated Cardiac Anomalies” under Morphology in Chapter 49 ) are excluded from this chapter.

Historical Note

A congenital coronary AV fistula was first described by Krause in 1865. The first report in the English literature was that of Trevor in 1912, who described autopsy findings in a case with a fistula from the right coronary artery into the right ventricle. The patient died from associated endocarditis. Autopsy reports from Blakeway and from Halpert followed. The first report of surgical correction was in 1947 by Biorck and Crafoord, who discovered a fistulous connection to the pulmonary trunk at thoracotomy in a patient presumed to have a patent ductus arteriosus. It was closed with sutures. Probably the first reported case of a fistula that was correctly diagnosed preoperatively was that of Fell and colleagues in 1958, and the first report of repair using cardiopulmonary bypass (CPB) was that of Swan and colleagues in 1959. Currarino and colleagues described the use of angiography in diagnosis in 1959.

Morphology

Coronary Artery Site

The right coronary artery or its branches are the site of the fistula in 50% to 55% of cases. The left coronary artery is involved in about 35%, and both coronary arteries in 5%. The fistulous artery is almost invariably part of a normally distributed coronary artery with a normal branching pattern. The fistula occurs either in the main vessel that continues beyond the fistula (a side-to-side pattern) or at the termination of the main vessel itself, or at a branch (an end artery). Rarely, the involved artery is anomalous. The coronary artery proximal to the fistula is always dilated and elongated and may be serpiginous, and the degree of these changes is roughly proportional to the size of shunt through the fistula. Usually, dilatation is uniform throughout, but it may become aneurysmal anywhere along its course. Rarely, a giant aneurysm occurs involving the whole artery. This is particularly prone to occur in fistulae from the right coronary artery entering either the posterior wall of the left ventricle or right ventricle ( Fig. 46-1 ). Although such aneurysms enlarge progressively, rupture is rare. Should the artery continue beyond the fistula, it reduces abruptly to a diameter smaller than expected. It is probable that in such cases a coronary steal phenomenon occurs. There is no convincing evidence that these “feeding arteries” are unusually susceptible to developing arteriosclerosis.

Size and Multiplicity of Fistulae

In surgically treated cases, the fistulous opening, when single, is seldom larger than 2 to 5 mm ( Fig. 46-2 ) and usually has fibrous margins, although uncommonly it may itself be aneurysmal as in the first reported case. Occasionally there may be several openings or a localized angiomatous network of vessels. Among the 58 patients reported from the Texas Heart Institute, multiple fistulae were identified in 16% and an angiomatous lesion in 10%; the fistula was aneurysmal in 19%. In a number of instances (no doubt many times the number reported in surgical series), the fistula is small and is recognized only because of high-quality cineangiography. As in other sites, most fistulae to the left ventricle are single. In a small group of patients, however, there is a diffuse spongework of tiny connections from a number of, if not most, branches of the left coronary and sometimes also the right coronary artery ( Fig. 46-3 ). These presumably represent persistence of embryonic trabecular spaces.

Clinical Features and Diagnostic Criteria

Diagnosis

Diagnosis is often strongly suspected from physical signs, but it may be difficult to distinguish coronary AV fistula from other lesions with rapid aortic runoff and continuous murmurs such as patent ductus arteriosus, ventricular septal defect with aortic regurgitation, ruptured sinus of Valsalva aneurysm, and in infancy, aortico–left ventricular tunnel. In coronary AV fistula, there is usually a continuous murmur that is maximal to the right of the sternum when the fistula enters the right atrium, and usually at the lower left sternal edge when it enters the right ventricle or left ventricle. However, when the pulmonary trunk is involved, the murmur is situated as in a patent ductus arteriosus. When the fistula enters the left ventricle, the murmur is usually only diastolic.

A systolic thrill is occasionally palpable when the fistula lies anteriorly (entry into right atrium or right ventricle). When the shunt and aortic diastolic runoff are large, pulse pressure is wide and the pulse jerky. Rarely, infants with a connection to the left ventricle may present with full-blown signs of severe aortic regurgitation.

The electrocardiogram (ECG) is entirely normal in about half of surgical patients and shows evidence of right or left ventricular overload in the remainder. The chest radiograph may also be normal or may show mild cardiomegaly and plethora. Cardiomegaly is more marked when heart failure appears. There may be evidence of right or left atrial enlargement, and occasionally the dilated and tortuous or aneurysmal coronary artery or fistulous site may distort the cardiac silhouette. This is most obvious when a giant aneurysm of the right coronary artery drains to the left ventricle, although this is rare.

Two-dimensional (2D) echocardiography can detect importantly enlarged coronary arteries and may also confirm specific chamber enlargement. Thus, diagnosis of a coronary AV fistula can be made by 2D and Doppler echocardiography if the fistula is large enough ( Fig. 46-4 ). Echocardiography, however, is not definitive.

Cardiac catheterization, aortography, and selective coronary angiography have long been the gold standard for definitive diagnosis and planning of either surgical repair or coil occlusion by interventional catheterization ( Figs. 46-5 and 46-6 ; also see Figs. 46-2 and 46-3 ). Left-to-right shunts are calculated, and right heart pressures are measured.

Computed tomography angiography (CTA) can accurately define the morphology of the fistula in both adults and young children ; in cases that will not require hemodynamic measurements to make management decisions, it may be the diagnostic procedure of choice.

Natural History

The natural history of coronary AV fistula is not known precisely, but its general outlines are clear. The fistula, if not present at birth, develops early in life. Likely, small fistulae remain small, and moderate fistulae slowly increase in size, although there may be little change over 10 to 15 years. Onset of dyspnea, heart failure, and angina can occur in young patients with large fistulae. However, because the shunt is usually only moderate, symptoms often do not appear until later in life consequent to long-standing moderate left ventricular volume overload. Daniel and colleagues found from a review of the literature that if heart failure did not occur early in infancy, it would be virtually unknown until age 20. The maximum prevalence of heart failure occurs in the fifth and sixth decades.

The other event that may precipitate symptoms and cause premature death is infective endocarditis, which occurs in about 5% of patients and may develop at any age. Aneurysm formation develops with increasing frequency over time, occurring in 9% of children and 14% to 29% of adults. Spontaneous rupture is rare, even though the feeding coronary artery or the fistula itself may become aneurysmal, and as with other aneurysms, there is progressive dilatation of the sac. Rupture has not been reported in children. Liberthson and colleagues found that among 173 reported patients with mean age 24 years, fistula-related death occurred in 6%: 1% in those presenting younger than age 20, and 14% in those presenting later (mean age 43 years). Spontaneous closure of a fistula has been recorded but is rare.

Technique Of Operation

Approach in all patients is through a median sternotomy, with preparation made for use of CPB (see “Preparation for Cardiopulmonary Bypass” in Section III of Chapter 2 ). After opening the pericardium, site of the fistula and location, size, and pathology of the coronary artery leading to it are noted. CPB is indicated:

• 1

  When the artery is dilated and tortuous, to prevent catastrophic hemorrhage during closure of the fistula

• 2

  When the fistula is relatively inaccessible, such as when it is in the left atrioventricular groove or distribution of the circumflex or distal right coronary artery

• 3

  When the fistula is in the course of the coronary artery rather than at its termination, so that the fistula itself can be closed without ligation of the coronary artery

• 4

  When an aneurysm requires excision

Precise location of the coronary AV fistula is determined and marked with a stitch before establishing CPB, because this is difficult to do later. After establishing CPB, the aorta is clamped. While the fistula is digitally closed, cold cardioplegic solution is administered. When the chamber into which the fistula opens is an atrium or the pulmonary trunk, the chamber is opened and the fistula closed from within with over-and-over sutures supplemented with a pledgeted mattress suture.

Cold cardioplegic solution can be infused both to identify the entry point of the fistula in the opened chamber and to test security of closure. When the fistula enters a ventricle or when the coronary artery is large and continues beyond the fistula, the coronary artery itself is opened and the fistula closed with a running suture, followed by closure of the arteriotomy with 6-0 or 7-0 polypropylene sutures. Use of a running mattress suture beneath the artery through the fistulous site is not recommended because this may lead to fistula recurrence.

Alternatively, if the fistula enters the right ventricle, right atrium, or pulmonary trunk, once CPB is established, the pulmonary trunk or right atrium, as appropriate, is opened without clamping the aorta. A pressurized blood stream emitted from the fistula makes its identification easy. This technique is especially helpful if the fistula enters the trabeculations of the right atrium or right ventricle. Closure from within the chamber is performed, and elimination of the blood stream confirms efficacy of closure.

When a large aneurysm is present (see Fig. 46-1 ), it should be excised. If the aneurysm is localized over the fistula site, excision entails trimming away the edges of the dilated vessel and resuturing its walls to create an artery of near-normal size. This is possible because the posterior wall invariably consists of strong tissue. This is necessary only when the artery continues beyond the site of the fistula. When it is an end artery, the aneurysm is completely excised and the vessel remnants oversewn. When the aneurysm involves most of the feeding coronary artery (see Fig. 46-1 ), there is usually no option but to unroof it completely and close the coronary artery proximal and distal to the sac, the latter closure including the fistula site. In such circumstances, it is always appropriate to consider use of coronary artery bypass grafting (CABG) using either a saphenous vein or internal thoracic artery to the vessel beyond the fistula, but this may not be possible when the coronary artery is too small.

After completing the repair, if a left-sided chamber has been opened, it is aspirated for air. The remainder of the operation is completed as usual (see “Completing Cardiopulmonary Bypass” in Section III of Chapter 2 ). Fistulous connection may be safely closed without CPB when it represents the termination of a major coronary artery branch into an easily accessible site and indicators for CPB are absent. In such instances, a suture ligature is placed around the “feeding” coronary artery very close to the fistulous connection. The fistula is then temporarily completely closed (verified by complete ablation of the thrill), and the ECG is monitored for several minutes. If there are no ECG changes, the ligature is tied down and another suture ligature placed for additional security. When the fistula is less clearly localized and consists of multiple vessels, secure closure requires a running suture that encompasses all involved vessels and the underlying wall.

Special Features of Postoperative Care

Patients are managed as described in Chapter 5 .

Results

Indications For Operation

Some believe that prognosis of a surgically untreated coronary AV fistula is excellent, and operation is indicated only if symptoms are present. However, in view of the probability that at least some of these fistulae will increase in size and therefore eventually produce symptoms and heart failure, the tendency for development of infective endocarditis, the low probability of spontaneous closure, and the safety and efficacy of operation, it is recommended that diagnosis of a coronary AV fistula is an indication for operation unless the shunt is small ( < 1.3).

Special Situations and Controversies

Use of various interventional catheter-delivered occluding devices and coils has been reported to treat coronary AV fistulae successfully. These techniques are increasingly being considered the therapy of choice for appropriately selected patients. In a nationwide survey conducted between 1996 and 2003, 85% of treated patients were managed surgically and 15% with interventional techniques.

Definition

In anomalous connection of left coronary artery to pulmonary trunk, the whole of the left main coronary artery or only the left anterior descending or circumflex branch connects anomalously to the proximal pulmonary trunk or very rarely to the proximal right pulmonary artery. Branching pattern of the anomalously connecting left coronary artery remains normal. The right coronary artery arises normally from the aorta and has a normal branching pattern. Collaterals from the right coronary artery feed the left coronary artery, in which flow is reversed, so that the left coronary artery drains into the pulmonary artery. Very rarely, both coronary arteries connect to the pulmonary artery by a single trunk.

Historical Note

In 1886, Brooks in Dublin described, apparently for the first time, anomalous connection of a coronary artery to the pulmonary trunk, and in 1908, Abbott described anomalous connection of left coronary artery to pulmonary trunk. Bland, White, and Garland in 1933 described the clinical syndrome associated with the anomaly, based on their experience with a 3-month-old infant who died from it. The pathophysiology, as suggested by Brooks in his original paper, is impoverished left ventricular myocardial blood flow—despite good collaterals between right and left coronary arteries—because of retrograde flow from left coronary artery to pulmonary trunk. Edwards supported this hypothesis, as did Case and colleagues in 1958. The latter also reported the postmortem observation that radiopaque dye injected into the ascending aorta passed out through the normal right coronary artery and, by collaterals, filled the left coronary artery in retrograde fashion.

Sabiston and colleagues verified retrograde flow at the first successful operation for the anomaly in 1959 by measuring a striking increase in left coronary artery pressure when its anomalous connection to the pulmonary trunk was occluded. Actual demonstration of left-to-right shunt into the pulmonary trunk was by Augustasson and colleagues in 1962 and by Rudolph and colleagues in 1963.

Earliest surgical attempts to ameliorate the condition were indirect. The first attempt was apparently by W.J. Potts, who created an aortopulmonary (AP) fistula to increase saturation in the pulmonary trunk (personal communication, 1955). Kittle and colleagues banded the pulmonary artery, and Paul and Robbins used pericardial poudrage. These procedures are obsolete.

Successful ligation of the anomalous left coronary artery connection by Sabiston and colleagues in 1959 was followed by a similar report from Rowe and Young in 1960. As early as 1953, Mustard reported attempts to anastomose the turned-down left common carotid artery to the anomalous left coronary artery that he detached from the pulmonary trunk together with a button of pulmonary trunk wall. Apley and colleagues attempted a similar procedure using the left subclavian artery in 1957. Meyer and colleagues first used this latter procedure successfully to create a two-artery coronary system in 1968, and others including Pinsky and colleagues reported such a repair.

In 1966, Cooley and colleagues reported use of coronary artery bypass vein grafting from the aorta to the left main or proximal left anterior descending artery, after closing the left coronary ostium from within the pulmonary trunk. The next procedure to evolve was translocation of the anomalous coronary artery from pulmonary trunk to ascending aorta. Such a procedure was performed unsuccessfully in 1972 using hypothermic circulatory arrest. This was first performed successfully for the rare condition of anomalous connection of the right coronary artery to pulmonary trunk (where the artery lies anteriorly and is more readily translocated) by Tingelstad and colleagues in 1971, and for the left coronary artery by Neches and colleagues in 1974. The latter also described successful interposition of a free left subclavian artery segment between the left coronary artery and the back of the ascending aorta.

In 1979, use of a tunnel within the pulmonary trunk to connect the ostium of the anomalous coronary artery to the aorta via an AP window was introduced. It was created either of pericardium, as described by Hamilton and colleagues, or of pulmonary artery wall, as described by Takeuchi and colleagues. Arciniegas and colleagues modified this concept by placing a free subclavian artery graft inside the pulmonary trunk. Reconstructive techniques have been devised to permit implanting coronary arteries that are remote from the aorta. Use of temporary ventricular assistance in infants has been an important adjunct to postoperative management. The aneurysmal left ventricular wall was excised unsuccessfully in 1960. This procedure, combined with ligation of the left coronary artery, was subsequently performed successfully by Turina and colleagues in 1973 and Fleming and colleagues in 1975.

Morphogenesis and Morphology