The electrocardiogram and coronary artery spasm.

This discussion does not attempt to explain why the ECG of patients during rest angina accompanied by coronary spasm sometimes demonstrates ST segment elevation, at other times less impressive changes and, on occasion, no important change. Regardless, the important point is that ECG changes during an episode of chest pain are not a necessary criterion for the diagnosis of angina pectoris either in patients presenting with rest or exertional chest pain syndromes.