A 55-year-old woman presented with profound congestive heart failure 23 years following mediastinal radiation. Ejection fraction (EF) was 35%. Symptoms markedly improved and EF increased to > 55% following saphenous vein bypass for > or = 80% ostial left main stenosis. Radiation therapy, a known risk factor for coronary atherosclerosis, may present with reversible severe silent ischemia.