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A 52 year old man presented with near syncope while standing in a bus. An ECG showed widespread T wave inversion involving lead V1–4, I, aVL. Myocardial infarction was ruled out on subsequent cardiac enzyme assays. A dobutamine stress echocardiogram showed abnormal wall motion in the left anterior descending artery territory during stress. Cardiac catheterisation showed a large right coronary artery collateralising the left coronary artery, which emptied into the pulmonary artery (panel). There was no significant coronary artery disease and the left ventricular systolic function was normal. The calculated left to right shunt (Qp:Qs ratio) was 1.07.
Anomalous left coronary artery from the pulmonary artery is a rare, congenital cardiac anomaly accounting for approximately 0.25–0.5% of all congenital heart disease. It 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. Collateral circulation between the right and left coronary systems ensues after birth and the left ventricular myocardium is chronically underperfused, since flow is preferentially directed into the pulmonary vascular bed and away from the left ventricular myocardium due to the low pulmonary vascular resistance (coronary steal phenomena). Left untreated, the mortality rate in the first year of life is 90% secondary to myocardial ischaemia or infarction and congestive heart failure. In rare cases, the clinical presentation of myocardial ischaemia may be delayed into early childhood, or even adulthood as in our patient, when intracardiac shunt is minimal.