Unusual congenital coronary artery anomaly in a young adult presenting as sudden cardiac arrest.

A previously asymptomatic young female with no previous medical or cardiac history collapsed during indoor exercise. A portable automatic external defibrillator showed a shockable rhythm. She received multiple electrical shocks with return to normal sinus rhythm without ischaemic ECG changes. Her troponin level was mildly elevated. A transthoracic echocardiogram revealed moderately reduced left ventricular ejection fraction with global hypokinesis. During emergent coronary angiography, the left main coronary artery could not be found. The right coronary artery was normal with robust collaterals to the entire left coronary circulation extending to the left main coronary artery, but did not fill the ostium. Coronary CT angiogram confirmed nearly complete absence of the left main coronary artery ostium. A diagnosis of left main coronary artery atresia was made. Patient underwent successful two vessel coronary artery bypass grafting. She continues to do well 1 year postoperatively.