Severe, resistant spasm of the left main coronary artery--a serious pitfall.

A case of severe, resistant spasm of the left main coronary artery, which was not relieved even after 600 micrograms of intracoronary nitroglycerine over 30 minutes, is described. The case was mistakenly taken for fixed stenosis and would have been subjected to percutaneous transluminal coronary angioplasty with stenting at the same sitting, had not the case been fortuitously deferred. On repeat angiography after one week, the left main was found to be normal. Some guidelines to avoid such a situation are suggested.