A 53-year-old man with no ischemic cardiac symptoms but dynamic ventricular repolarization changes in Holter monitoring underwent cardiac investigation prior to elective non cardiac surgery. Invasive coronary angiography followed by computed tomography coronary angiography showed left main stem atresia with collaterals from the right coronary artery supplying retrogradely the left coronary circulation. The echocardiogram showed no alterations. Cardiac magnetic resonance myocardial perfusion imaging showed no ischemia. During the 18-month follow-up period, the patient remained asymptomatic for ischemic events and therefore no intervention was deemed necessary.