Background
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:
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The left anterior descending or circumflex branches
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The right coronary, often discovered as an incidental finding on autopsy
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Both the right and left coronary arteries, a circumstance not compatible with survival
Pathophysiology
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]
Etiology
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]
Epidemiology
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.
Prognosis
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:
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Surgical ligation
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Bypass grafts that may become occluded or stenotic
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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.
Patient Education
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.
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Preoperative electrocardiogram in a 2-month-old infant with anomalous origin of the left coronary artery from the pulmonary artery demonstrating pathologic Q waves in leads I and aVL and diffuse ST-T wave changes consistent with an anterolateral infarction.
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Electrocardiogram in 2-month-old infant with anomalous origin of the left coronary artery from the pulmonary artery 17 months following successful surgical revascularization, demonstrating complete resolution of the anterolateral infarction pattern and ST-T wave changes.
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Two-dimensional echocardiographic image (parasternal short axis view) in a patient with anomalous origin of the left coronary artery arising from the pulmonary artery (ALCAPA). The left coronary artery (white arrow) appears to course towards the main pulmonary artery (MPA) just above the pulmonary valve and not to the aortic root (Ao). RV = Right ventricle.
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Two-dimensional echocardiographic image with color flow mapping (parasternal short axis view) in the same patient with anomalous origin of the left coronary artery arising from the pulmonary artery (ALCAPA). The addition of color flow mapping to the 2-dimensional image demonstrates abnormal flow reversal within the left coronary artery (white arrows) towards the main pulmonary artery (MPA) just above the pulmonary valve. RV = Right ventricle. Ao = Aortic root.
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Doppler interrogation of the abnormal color flow jet is depicted, demonstrating abnormal flow within the main pulmonary artery towards the transducer in diastole, which represents runoff from the anomalous left coronary artery (large white arrowhead). Small white arrow: Normal antegrade main pulmonary artery flow in systole. MPA = Main pulmonary artery.
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Aortogram in a patient with suspected anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA). Frontal (left panel) and lateral (right panel) images demonstrating an enlarged right coronary artery (small white arrow), which fills a small left coronary system (solid arrow head) via collaterals with eventual faint opacification of the main pulmonary artery (not demonstrated in this frame).
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Main pulmonary artery angiogram demonstrating the technique of stop flow angiography. There is retrograde opacification of the entire left coronary artery system, which originates from the distal main pulmonary artery (MPA), including the anterior descending (solid white arrowhead) and circumflex (small white arrow) branches. Left panel: Frontal image. Right panel: Lateral image.
