PEDIATRICS: CARDIAC DISEASE & CRITICAL CARE MEDICINE ARTICLES

Introduction

Background

Anomalous origin of the left coronary artery arising from the pulmonary artery (ALCAPA) is a rare but serious congenital 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 By 1962, Fontana and Edwards reported a series of 58 postmortem specimens that demonstrated that most patients had died at a young age.²

Presently, the prognosis for patients with ALCAPA is 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

Pathophysiology

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 (2) relatively equivalent 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.

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.

Frequency

United States

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.

Mortality/Morbidity

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 CHF. Sudden death may occur because of inadequate collateral circulation between the left and right coronary artery systems.

Race

No predilection is known.

Sex

Occurrence is generally similar between males and females and is not considered an inheritable congenital cardiac defect.

Age

Approximately 85% of patients present with clinical symptoms of CHF 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. Rarely, a patient may stabilize following infarction and present with mitral valve regurgitation later in childhood or even adulthood.

Clinical

History

• 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 (CHF), 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.

Physical

• If 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.
• 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.

Causes

• Inheritance is not a factor. For example, if 2 family members are affected, the fact that they are within the same family did not have a role in their development of the condition.
• In utero exposure to teratogens, chromosomal abnormalities, or other risk factors are unrelated to ALCAPA.
• An isolated congenital cardiac defect, including 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.³