Marked alternans of the elevated ST segment during occlusion of the left anterior descending coronary artery in percutaneous transluminal coronary angioplasty: clinical background and electrocardiographic features.

To investigate the clinical background and the electrocardiographic features of marked alternans of the elevated ST segment during coronary angioplasty, we examined 12-lead electrocardiograms recorded continuously during occlusion of the left anterior descending coronary artery by balloon inflation in 41 patients. The incidence of marked ST alternans was 27% of 41 patients and 15% of 117 balloon occlusions. The incidence decreased progressively from the first to the third occlusion. The time course of ST alternans was determined. Compared with patients without ST alternans, patients with ST alternans had a shorter history of angina, less severe stenosis of the target lesion before coronary angioplasty, more leads showing ST elevation during occlusion, higher ST elevation during occlusion and lower incidence of previous myocardial infarction in the left anterior descending coronary arterial area. ST alternans recorded on the surface electrocardiogram may thus be considered a marker of acute severe and extensive myocardial ischemia.