A Middle-Aged Man With Pulseless VT and Dual Pathology: Anomalous Left Main Coronary Artery From Right Coronary Cusp With Transseptal Course and Underlying Dilated Cardiomyopathy.

Anomalous aortic origin of a coronary artery from the opposite sinus (AOCAOS) is a rare variety of coronary artery anomalies. Left main coronary artery (LMCA) arising from right coronary cusp (RCC) with a transseptal course is an uncommon variant that may not be as benign as previously thought. The coexistence of AOCAOS with dilated cardiomyopathy (DCM) is exceptionally rare and presents diagnostic and therapeutic challenges. Herein, we present a 43-year-old man with a history of Type 2 diabetes mellitus and chronic substance use who was admitted after successful resuscitation from pulseless ventricular tachycardia (VT). Initial workup revealed severely reduced left ventricular ejection fraction (LVEF) of 20% on echocardiography. Invasive coronary angiography demonstrated anomalous origin of the LMCA from the RCC. Cardiac magnetic resonance (CMR) confirmed the diagnosis of DCM with no evidence of fibrosis, and coronary computed tomography angiography (CCTA) delineated a transseptal course of the anomalous LMCA. The patient was managed medically for heart failure and underwent cardiac resynchronization therapy defibrillator (CRT-D) implantation for primary prevention of sudden cardiac death. At 3-month follow-up, he showed significant clinical improvement. This case underscores the importance of a comprehensive diagnostic approach in sudden cardiac death survivors and highlights that transseptal AOCAOS may not be benign when associated with cardiomyopathy. Coronary CTA and CMR are essential tools for complete evaluation.