"Superdominant" Left Anterior Descending Artery Continuing as Posterior Descending Artery: Extremely Rare Coronary Artery Anomaly

The posterior descending artery (PDA) supplying the posterior one-third of the inter-ventricular septum usually arises from the right coronary artery (RCA) or the left circumflex artery (LCX). PDA arising from the left anterior descending artery (LAD) is an extremely rare anomaly. Here we report a rare type of left dominant circulation in which a large LAD is continuing as PDA after winding round the apex in the presence of a diminutive RCA. Such a large LAD continuing as PDA is referred as "hyperdominant" or "superdominant". A 32-year-old male chronic smoker presented with acute onset retrosternal pain of 4 h duration with profuse sweating in primary health center with electrocardiography (ECG) changes in inferior leads and was thrombolysed with intravenous streptokinase 15 lacs IU over one hour and was referred to our center for further management and coronary intervention. Coronary angiogram revealed PDA as a continuation of the LAD beyond the crux and a non-dominant right coronary as well as LCX. The LAD had plaque in mid-LAD course. Intravascular ultrasound study (IVUS) showed insignificant plaque in mid-LAD (30%). Hence, we decided to keep him on medical therapy only.