Left Main Coronary Artery Disease (LMCAD) : Stenosis of 50 per cent or more of the left main coronary artery is an indication. If or surgery. Results of medical management are very poor and angioplasty is hazardous in these patients. Even if patient is asymptomatic or when angina is well controlled with medication, early surgery is indicated. The operation has to be done urgently if' there is critical left main lesion.