Myocardial Ischemia In Children: Anomalous Left Coronary Artery From Pulmonary Artery (ALCAPA)- Dr Murtaza Kamal
Bland White Garland syndrome or (ALCAPA) is a congenital anomaly of the heart’s arterial supply in which the left coronary artery arises from the pulmonary artery. Worldwide its incidence is believed to be 1/3,00,000 live births. The part of the left ventricle which is supplied by this artery is thin, scarred and dilated and is a cause of myocardial ischemia in children. It is usually an isolated congenital anomaly. Sometimes it might be associated with patent ductusarteriosus, ventricular septal defect, tetralogy of fallout or coarctation of the aorta.
The cause of myocardial ischemia in this condition is not due to the perfusion by deoxygenated blood or due to a single normally functioning coronary artery i.e. the right coronary artery, but is due to the direction of blood flow through the coronary bed. Owing to the increased pulmonary arterial pressures, in the fetal and early neonatal life, there is antegrade flow into the anomalous coronary artery from the pulmonary artery. Later as the neonatal pulmonary vascular resistance decrease, there is a parallel fall in blood flow in the anomalous left coronary artery. The perfusion of cardiac myocardium at this stage depends entirely on the right coronary artery. Hence, ischemia is the fate unless there is adequate circulation from right to left coronary artery via anastomosis. Initially, ischemia is transient which occurs mainly during feeding, crying, and exertion. The left coronary artery is connected to a low-pressure pulmonary artery, so this collateral flow tends to pass into the pulmonary artery rather than into higher pressure myocardial blood vessels.
There can be three types of presentation of these patients. Firstly, they can present with serious symptoms in the initial days of life. History is of acute episodes of irritability and pallor which occurs secondary to myocardial ischemia, typically during feeding and distress. 80-85% of these children will not survive their infancy without treatment. Poor growth and development due to congestive heart failure is seen. The other group of children can present with early symptoms initially, followed by gradual disappearance of symptoms. Approximately 10% of children will have absence of early symptoms with asymptomatic survival till adulthood. Adults can present with mitral regurgitation, angina, myocardial infarction, congestive cardiac failure, atrial fibrillation, ventricular tachyarrhythmia. 33% of these adults will have sudden cardiac death.
Children are found to have rapid labored breathing, weak cry, cough, and diaphoresis. Pallor is seen with episodes of symptomatic myocardial ischemia. Congestive heart failure with raised jugular venous pressure is seen in these children. Pulmonary arterial hypertension and right ventricular enlargement are the features in ALCAPA. Pan-systolic murmur due to mitral regurgitation and continuous murmur due to coronary anastomosis are present.
ECG shows deep narrowed q waves in leads I, aVL, V4 and V5 with q wave width of >30 msec in lead I and a depth of > 3 mm I aVL with a QR pattern in aVL. Left ventricular hypertrophy is due to selective replication of postero-basal left ventricle by immature cardiocytes in response to hypoxia. Left atrial dilatation is also a feature. Abnormal R waves and R wave progression in left precordial leads with ST elevation and T wave inversion are commonly seen. Even in asymptomatic adults, resting ECG is often found to be abnormal. Massive cardiomegaly with features of pulmonary venous congestion is evident on CXR. With 2D echocardiography, the diagnosis has become rapid and much simplified. 2D Echocardiography can easily identify the pulmonary origin of the left coronary artery.
Doppler flow interrogation shows continuous or diastolic flow entering the pulmonary trunk just distal to the pulmonary valve and adhering to the medial wall of the pulmonary trunk. The left ventricle is dilated. Antero-lateral papillary muscle is seen to be echogenic due to ischemic scarring. Mitral regurgitation is seen. Ejection fraction is decreased severely. The right coronary artery is seen to be dilated with increased flow. Strain and stress echo can detect regional myocardial abnormalities in adults with normal left ventricular global function.CT and CMR have a useful role to play in adolescents and adults with compromised echo windows. CT has a rapid acquisition time and high resolution but it has radiation hazard. CMR is free of radiation hazard and helps in functional assessment of left ventricle and myocardium viability (late gadolinium enhancement). A cardiac angiogram is the gold standard for diagnosis in which selective right coronary arterial angiogram is diagnostic with dilated RCA and left to right shunt at pulmonary arterial level.
Surgery is the modality of treatment. Initial the aim was to decrease the pulmonary steal by pulmonary arterial banding and ligation of the origin of the left coronary artery. Later, along with the ligation of the origin of the left coronary artery, revascularization via an internal mammary artery or saphenous venous grafts was taken. Presently, direct reimplantation of left coronary artery origin into the aorta with a pulmonary arterial button around it is being done across the globe. The surgical mortality has drastically reduced from 75-80% in the early 1980s to 0-23% now. Early age at operation and decreased preoperative left ventricular function are the risk factors of early mortality. Mitral regurgitation improves with time. Left ventricular function normalizes by 1-2 years. Late coronary stenosis and graft occlusion presents as symptoms of ischemia and decreased left ventricular function, which warrants an assessment of coronary patency.
CONCLUSION: ALCAPA has very high mortality in infancy. 2D echocardiography has made the diagnosis very easy and feasible. Surgery is the main therapy and the surgical results have tremendously improved in the last 40 years. Overall long term prognosis of these patients is good.
Dr Murtaza Kamal is MBBS, MD (Paediatrics), DNB (Paediatrics), DNB-SS (Fellow Peds Cardio) Pediatric Cardiologist Star Hospitals. He is a member Editorial Board, Pediatrics at Specialty Medical Dialogues.