Iatrogenic left main coronary artery dissection is a rare entity for cardiac surgery but could cause severe low cardiac output and a catastrophic outcome. There is no conclusive strategy about how to manage such a condition. Here, we report a middle-aged woman who manifested with severe low cardiac output after aortic and mitral valve replacement surgery. She was subsequently diagnosed with extensive left main coronary artery dissection involving the left anterior descending artery and left circumflex artery, which resulted in large extension of myocardial infarction. The complex and dangerous vascular lesion was successfully treated by bailout stenting.