Anomalous Left Coronary Artery From the Pulmonary Artery

Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare but serious congenital cardiac anomaly.

ALCAPA was first described in 1866. The first clinical description in conjunction with autopsy findings was described by Bland and colleagues in 1933, so the anomaly is also called Bland-White-Garland syndrome.[1] In 1962, Fontana and Edwards reported a series of 58 postmortem specimens that demonstrated that most patients had died at a young age.[2]

The prognosis for patients with ALCAPA has dramatically improved as a result of both early diagnosis using echocardiography with color flow mapping and improvements in surgical techniques, including myocardial preservation.

The ALCAPA anomaly may result from (1) abnormal septation of the conotruncus into the aorta and pulmonary artery, or from (2) persistence of the pulmonary buds together with involution of the aortic buds that eventually form the coronary arteries.

ALCAPA is usually an isolated cardiac anomaly but, in rare incidences, has been described with patent ductus arteriosus, ventricular septal defect, tetralogy of Fallot, and coarctation of the aorta. Extremely rare variations of anomalous origin of the coronary arteries from the main pulmonary artery include the following:

• The left anterior descending or circumflex branches

• The right coronary, often discovered as an incidental finding on autopsy

• Both the right and left coronary arteries, a circumstance not compatible with survival

Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) does not present prenatally because of the favorable fetal physiology that includes (1) equivalent pressures in the main pulmonary artery and aorta secondary to a nonrestrictive patent ductus arteriosus and high pulmonary vascular resistance, and (2) relatively similar oxygen concentrations due to parallel circulations. This results in normal myocardial perfusion and, therefore, no stimulus for collateral vessel formation between the right and left coronary artery systems is present.

Shortly after birth, as the circulation becomes one in series, pulmonary artery pressure and resistance decrease, as does oxygen content of pulmonary blood flow. This results in the left ventricular myocardium being perfused by relatively desaturated blood under low pressure, leading to myocardial ischemia; low pressure is more important in causing decreased myocardial perfusion.

Initially, myocardial ischemia is transient, occurring during periods of increased myocardial demands, such as when the infant is feeding and crying. Further increases in myocardial oxygen consumption lead to infarction of the anterolateral left ventricular free wall. This often causes mitral valve papillary muscle dysfunction and variable degrees of mitral insufficiency.

Collateral circulation between the right and left coronary systems ensues. Left coronary artery flow reverses and enters the pulmonic trunk due to the low pulmonary vascular resistance (coronary steal phenomena). As a result, left ventricular myocardium remains underperfused. Consequently, the combination of left ventricular dysfunction and significant mitral valve insufficiency leads to congestive heart failure (CHF) symptoms (eg, tachypnea, poor feeding, irritability, diaphoresis) in the young infant. Inadequate myocardial perfusion likely causes significant chest pain and these symptoms of myocardial ischemia may be misinterpreted as routine infantile colic.[3]

Inheritance is not a factor for anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA). For example, if two family members are affected, the fact that they are within the same family did not have a role in their development of the condition. The condition is generally considered to be on the basis of multifactorial inheritance, similar to other congenital heart defects.

In utero exposure to teratogens, chromosomal abnormalities, or other risk factors are unrelated to ALCAPA.

Other congenital cardiac defects, such as patent ductus arteriosus, ventricular septal defect, tetralogy of Fallot, or coarctation of the aorta, rarely may be associated with ALCAPA. No specific association with any noncardiac anomalies is noted.[4]

United States data

Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare, congenital cardiac anomaly accounting for approximately 0.25-0.5% of all congenital heart disease. The incidence of ALCAPA does not vary geographically. ALCAPA is not considered an inheritable congenital cardiac defect. No risk factors for the occurrence of ALCAPA in any individual family are known, and ALCAPA is not associated with any syndromes or noncardiac conditions.

Race-, sex-, and age-related demographics.

There is no known racial predilection.

The occurrence of ALCAPA is generally similar between males and females, and it is not considered an inheritable congenital cardiac defect.

Approximately 85% of patients present with clinical symptoms of congestive heart failure within the first 1-2 months of life. In unusual cases, the clinical presentation with symptoms of myocardial ischemia may be delayed into early childhood. Though rare, presentation in adults have been reported.[5, 6, 7, 8] Rarely, a patient may stabilize following infarction and present with mitral valve regurgitation later in childhood or even adulthood.

Morbidity/mortality

Early diagnosis of anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) using echocardiography with color flow mapping and improvements in surgical techniques (eg, myocardial preservation) dramatically improve prognosis.

Left untreated, the mortality rate in the first year of life is 90% secondary to myocardial ischemia or infarction and mitral valve insufficiency leading to congestive heart failure. Sudden death may occur because of inadequate collateral circulation between the left and right coronary artery systems and/or development of arrhythmia.

Complications

Complications are rare. The need for future valve surgery depends on the occurrence of hemodynamic complications (eg, residual mitral valve insufficiency precipitated by permanent damage of the mitral valve architecture) following surgery.

Late complications related to coronary artery insufficiency are more likely to occur if revascularization was accomplished by any of the following:

• Surgical ligation

• Bypass grafts that may become occluded or stenotic

• Intrapulmonary tunnel technique, which may cause supravalvar pulmonary stenosis or, less commonly, become obstructed at the surgically created aortopulmonary window

Inadequate growth of the coronary anastomosis is possible, although unlikely, if surgical reimplantation of the left coronary artery was performed. This occurrence is similar to the rare reports of late coronary artery problems following the arterial switch procedure for transposition of the great vessels that also requires direct coronary transfer and reimplantation.

All patients should undergo formal exercise stress testing at an appropriate age as an aid in determining an appropriate exercise program.

Long-term physical restrictions, including restrictions of participation in competitive sports, are a direct function of whether myocardial ischemia is evident at rest or during exercise.

No dietary restrictions are necessary following successful surgical revascularization with subsequent clinical improvement.

Infants with anomalous left coronary artery from the pulmonary artery (ALCAPA) usually do well for a short period then gradually become fussy and irritable. Typically, they may display pallor, irritability, and diaphoresis after feeding, which are often attributed to colic.

Signs and symptoms of congestive heart failure, including tachypnea, tachycardia, diaphoresis, and poor feeding, eventually ensue, leading to poor weight gain. Usually no obvious evidence of a systemic illness is noted.

In rare instances, children outgrow these symptoms and gradually become asymptomatic, although periodic dyspnea, angina pectoris, syncope, or sudden death may still occur in adulthood.

If congestive heart failure (CHF) is present, the infant appears distressed and exhibits tachypnea, tachycardia, diaphoresis, and irritability.

Auscultation may demonstrate a systolic murmur of mitral valve regurgitation and, possibly, a diastolic rumble of relative mitral stenosis best located at the apical left precordial region. A moderate third heart sound may be heard.

Rarely, a soft continuous murmur may be detected at the upper left sternal border that is reminiscent of a coronary artery fistula or a small patent ductus arteriosus.

The left ventricular precordial impulse may appear prominent and displaced both inferiorly and laterally.

The second heart sound may seem narrowly split with increased intensity of the pulmonic component, if left ventricular failure causes pulmonary artery hypertension secondary to elevated left atrial pressure.

In cases of severe CHF, hepatic enlargement may be observed, and the peripheral pulses may be diminished in intensity secondary to low cardiac output.

Cardiac isoenzymes

Laboratory blood tests are not definitive in the diagnosis of anomalous left coronary artery arising from the pulmonary artery (ALCAPA).

Although elevation of creatine kinase (CK), MB, or troponin occurs following infarction of cardiac muscle, these tests should not be exclusively used for diagnostic purposes.

Twelve-lead electrocardiography

Typically, an anterolateral infarct pattern with abnormal deep (>3 mm) and wide (>30 msec) q waves is observed in leads I, aVL, V5, and V6, absent q waves in leads II, III, and aVF, and poor R wave progression across the precordial leads, with sudden shift to qR. Electrocardiography (ECG) detects abnormalities of repolarization in the form of ST-segment depression or inversion, both inferior and lateral (see the image below). The QRS axis is typically normal, although, in some cases, a left superior axis is seen.

Following successful surgical revascularization, the ECG may revert to normal findings with the disappearance of the pathologic q waves and ST-T wave changes (see the image below).

Chest radiography

Chest radiography usually demonstrates cardiomegaly, with or without pulmonary venous congestion, although this is not diagnostic for anomalous left coronary artery arising from the pulmonary artery (ALCAPA).

Cardiovascular magnetic resonance imaging

Cardiovascular magnetic resonance imaging (CMRI) is a good, noninvasive, radiation-free investigation in the postsurgical evaluation of ALCAPA. In referred patients, basal, anterolateral subendocardial myocardial fibrosis is a characteristic finding. Furthermore, stress adenosine CMRI perfusion, can identify reversible ischemia in this group, and is indicative of left coronary artery occlusion.[12]

Two-dimensional echocardiography with Doppler color flow mapping

This test often is diagnostic and, in some situations, replaces the need for cardiac catheterization and angiography.

Echocardiography without Doppler may identify abnormal origin of the left coronary artery from the main pulmonary artery (see the image below). In unusual circumstances, the anomalous coronary may arise from a branch pulmonary artery, making echocardiographic diagnosis difficult, even with Doppler.

The use of color flow velocity mapping can be diagnostic, demonstrating retrograde flow from the anomalous left coronary into the pulmonary trunk. The retrograde flow into the pulmonary trunk is typically directed in an unusual orientation within the main pulmonary artery (see the image below), distinguishing it from the diagnosis of a patent ductus arteriosus.

Doppler mapping of an abnormal color flow jet will usually identify abnormal retrograde flow within the main pulmonary artery in both late systole and diastole (see the image below). The mapping image partially depends on pulmonary artery pressure.

The presence of retrograde flow is dependent on the development of collaterals between the left and right coronary artery systems. If collateralization has not occurred, as may be the case with a very early age presentation, this finding may be absent.

Abnormal dilation of the proximal right coronary artery, when present, reflects development of extensive collateralization between the right and left coronary artery systems in those patients who present later in infancy or in childhood.

An additional finding, which is not sensitive but highly specific, is abnormal "brightness" (echogenicity) of left ventricular papillary muscles and sharply delimited sectors of the left ventricular endocardial surface.

Variable degrees of mitral valve regurgitation, left ventricular dysfunction, and wall motion abnormalities may be identified.[13]

Although the echo-Doppler studies are excellent tools in diagnosing ALCAPA, sometimes they may mislead the echocardiographer with seemingly normal origin of left coronary artery. When clinical suspicion of ALCAPA is high, an alternative imaging technique such as cardiac catheterization with angiography or MRI should be performed—even with seemingly “normal” origin of left coronary artery.

Contrast echocardiography of the main pulmonary artery demonstrating negative contrast secondary to flow from the ALCAPA may also be used to diagnose this condition.[14]

Cardiac catheterization and angiography

Angiographic evaluation of the coronary artery system should be performed despite a negative echocardiogram if either the clinical history or electrocardiography (ECG) is strongly suggestive.[15]

Hemodynamic measurements are usually consistent with low cardiac output and elevated left atrial pressures secondary to reduced left ventricular compliance or significant mitral valve insufficiency.

Oximetry may show a small left-to-right shunt into the pulmonary arteries.

Aortography or selective right coronary arteriography usually demonstrates an enlarged right coronary artery system with collateralization to the left coronary artery and eventual reflux of contrast into the pulmonary arterial system (see the image below).

If collateralization has not occurred, identification of the anomalous left coronary artery may not be evident by aortography or selective right coronary arteriography.

Stop flow angiography

With a large bolus of contrast under high pressure, an alternative approach is to perform a balloon occlusion angiogram within the distal main pulmonary artery, which retrogradely should fill the anomalous left coronary artery (see the image below).

Although rare, false-negative results with this technique may be caused by incomplete occlusion of the main pulmonary artery or by balloon malposition. A balloon positioned in the proximal main pulmonary artery may occlude the orifice of the anomalous left coronary. Alternatively, if the anomalous left coronary artery arises from the left pulmonary artery, positioning the balloon in the distal main pulmonary artery may prevent contrast from entering the coronary artery.[16]

The severity of symptoms in patients with anomalous left coronary artery from the pulmonary artery (ALCAPA) at presentation determines whether the patient is admitted to an intensive care unit (ICU) for aggressive medical management of congestive heart failure (CHF) before surgical revascularization.

Initial postoperative management occurs in a pediatric ICU until the patient is extubated and no longer requires intravenous inotropic support or antiarrhythmics.

Following surgical revascularization, postoperative care includes the short-term use of inotropes (eg, oral digoxin), diuretics, and afterload reduction medication (eg, angiotensin converting enzyme [ACE] inhibitors) to improve cardiac output and to eliminate the preoperative symptoms of CHF.

Monitor continuously during the immediate postoperative period, because there is a risk, although unusual, of cardiac dysrhythmia secondary to preoperative myocardial ischemia or infarction.

Initial management of anomalous left coronary artery from the pulmonary artery (ALCAPA) is both supportive and temporary. Treatment of congestive heart failure includes carefully using diuretics, afterload reduction medications, and inotropic drugs.

Although systemic oxygen transport may be reduced in the presence of low systemic blood flow, using 100% oxygen may be deleterious. Oxygen may further reduce pulmonary vascular resistance and magnify coronary steal from the right coronary artery into the pulmonary arteries.

A similar phenomenon occurs with aggressive afterload reduction, during which right coronary artery perfusion may be reduced, leading to decreased left coronary blood flow.

Inotropic support, however, may significantly increase myocardial oxygen consumption, which, in the presence of reduced myocardial blood flow, may result in worsening ischemia.

Increasing reports of catheter intervention for this lesion are emerging. The results in these instances remain conflicting. Surgical intervention remains the procedure of choice.

Consultations

Consult with a pediatric cardiologist and a pediatric cardiothoracic surgeon.

Diet and activity

No specific postoperative dietary restrictions are usually necessary.

Activity restrictions are directly related to the severity of left ventricular dysfunction and postoperative mitral valve insufficiency. No specific activity recommendations are necessary because the majority of patients are infants. For patients who are able to participate in exercise or competitive sports or those with residual postoperative hemodynamic problems, consider recommending avoidance of significant isometric activities.

Spontaneous resolution of congestive heart failure (CHF) symptoms is rare. Surgical revascularization of the left coronary artery system is usually necessary. Once the patient is stabilized, perform surgical revascularization to create a two–coronary artery system. Over the years, various techniques for this have been advocated.

Ligation of the left coronary artery at its origin from the main pulmonary artery is an original technique, performed without the use of cardiopulmonary bypass. However, this surgical option is no longer recommended: The long-term results were not optimal since myocardial perfusion remained solely dependent on extensive collateralization from the right coronary artery, and the patient remained at risk for ischemic episodes and sudden death.

Current surgical procedures are directed at establishing revascularization by creating a two–coronary artery system via either (1) a left subclavian artery-coronary artery anastomosis, (2) a saphenous vein bypass graft, (3) Takeuchi procedure (creation of an aortopulmonary window and an intrapulmonary tunnel extending from the anomalous ostium to the window), or (4) direct reimplantation.[17] By establishing a patent two–coronary artery system, most patients experience normalization of left ventricular systolic function, thereby improving long-term survival.

The need for simultaneous mitral valve reconstruction, in the presence of severe insufficiency, is controversial because spontaneous improvement of mitral valve function often occurs following surgical revascularization.

Once revascularization to a two–coronary artery system is accomplished, most patients demonstrate improved left ventricular systolic function, decreased mitral valve insufficiency, and resolution of CHF symptoms. In many cases, the classic infarct pattern on electrocardiography eventually disappears following normalization of left coronary blood flow (see the image below). Occasionally, persistent refractory mitral regurgitation will necessitate delayed mitral valve repair or replacement.

A study of 23 infants indicated that in patients with anomalous left coronary artery from the pulmonary artery (ALCAPA), aortic reimplantation of the anomalous coronary artery is an effective means of improving myocardial function but is a less effective tool for treating severe mitral valve regurgitation. In 16 infants, the anomalous artery was directly implanted into the ascending aorta, while the seven remaining patients underwent repair with a trapdoor flap or tubular extension technique. The investigators evaluated left ventricular function and degree of mitral valve regurgitation over a 10-year follow-up period. Four of the patients died early in the postoperative period (within 12 days after surgery), but improvement in myocardial function was seen in all of the remaining patients. However, of five infants diagnosed preoperatively with severe mitral valve regurgitation, only one demonstrated improvement in this condition; two patients required mitral valve replacement.[18]

In another study, a comparison of coronary transfer and Takeuchi repair (intrapulmonary tunnel) revealed equal improvement of left ventricular function and resolution of mitral valve regurgitation in both groups.[19] However, patients undergoing the Takeuchi technique developed significant pulmonary regurgitation, whereas those that had coronary transfer did not develop this complication.[19]

Postoperative care, precautions, and complications

Diuretics, and afterload reduction may be necessary until there is significant improvement in left ventricular systolic and diastolic function with resolution of mitral valve insufficiency. These medications improve cardiac output and eliminate the preoperative symptoms of congestive heart failure.

Although unusual, there remains a risk of cardiac dysrhythmia secondary to preoperative myocardial ischemia or infarction. Monitor continuously in the immediate postoperative period.[4, 20, 21, 22]

The clinical status of the patient, in relation to residual CHF symptoms, determines the frequency of postoperative outpatient follow-up visits.

Most patients do not require frequent cardiac evaluation following surgical revascularization once ventricular function and mitral valve insufficiency is dramatically improved. However, follow-up reevaluation, although infrequent should be performed.

Medications used at the time of presentation in patients with anomalous left coronary artery from the pulmonary artery (ALCAPA), including the judicious use of diuretics, focus on afterload reduction and inotropic support for the treatment of congestive heart failure (CHF) symptoms. Except for diuretics, medications may have immediate deleterious effects that could lead to worsening myocardial ischemia, further reductions in cardiac output, and the potential for ventricular arrhythmias. Following surgical revascularization, these same medications may be used more aggressively for the continued treatment of CHF, left ventricular dysfunction, and mitral valve insufficiency.

Class Summary

These agents promote excretion of water and electrolytes by the kidneys. They are used to treat heart failure or hepatic, renal, or pulmonary disease when sodium and water retention has resulted in edema or ascites. These medications ease the work of breathing by decreasing the degree of pulmonary venous congestion (pulmonary edema) secondary to mitral valve insufficiency or elevated left atrial pressures resulting from diminished left ventricular compliance. Diuretics also may decrease systemic venous congestion (preload reduction) if right heart failure also has occurred.

Furosemide (Lasix)

Increases excretion of water by interfering with chloride-binding cotransport system, which, in turn, inhibits sodium and chloride reabsorption in ascending loop of Henle and distal renal tubule. Diuretic effect occurs within 10-20 min following an IV dose and peaks 1-1.5 hours later.

Class Summary

These agents improve preoperative or postoperative cardiac output by reducing systemic vascular resistance and increasing systemic blood flow resulting from myocardial dysfunction and/or significant mitral valve insufficiency. Nitrates are peripheral and coronary vasodilators used in the management of angina pectoris, heart failure, and myocardial infarction. ACE inhibitors are beneficial in all stages of chronic heart failure. Pharmacologic effects result in a decrease in systemic vascular resistance, reducing blood pressure, preload, and afterload. Dyspnea and exercise tolerance are improved.

Nitroprusside (Nitropress)

Vasodilator of choice for severe, low-output, left-sided heart failure, providing that the arterial pressure is reasonably maintained. Rapidly acts and has a balanced effect, dilating both arterioles and veins. Because of an increase in stroke volume, considerable hemodynamic improvement without much hypotension may occur. In general, some decrease in blood pressure occurs, which may limit therapeutic effect. No PO equivalent is available.

Captopril (Capoten)

Angiotensin converting enzyme (ACE) inhibitors have a major role as a peripheral vasodilator in hypertension and CHF. They act on angiotensin-renin-aldosterone system by inhibition of ACE. Prevents conversion of angiotensin I to angiotensin II, a potent vasoconstrictor, resulting in increased levels of plasma renin and a reduction in aldosterone secretion. This is most beneficial when CHF is accompanied by high plasma renin activity that leads to increased sympathetic activity, aldosterone release, and peripheral vasoconstriction. Use of ACE inhibitors usually is reserved for long-term postoperative management, at which point, the severity of myocardial dysfunction and mitral valve insufficiency has improved significantly to allow the use of PO medications.

Milrinone

Bi-pyridine positive inotrope and vasodilator with little chronotropic activity. Different in mode of action from both digitalis glycosides and catecholamines. Selectively inhibits phosphodiesterase type III (PDE III) in cardiac and smooth vascular muscle, resulting in reduced afterload, reduced preload, and increased inotropy.