S-T segment elevation and coronary spasm in response to exercise

The prevalence rate of exercise-induced S-T segment elevation of 0.1 mV or greater in symptomatic patients is 3.0 to 6.5 percent in most studies. S-T segment elevation is associated with a more severe degree of myocardial ischemia than depression and frequently implies a high grade coronary stenosis in the vessel that supplies the site of ischemia. Leads V₄ to V₆ and bipolar lead CM₅ have been found to be relatively insensitive in detecting exercise-induced S-T segment elevation.

The pathogenesis of S-T segment elevation is different in three clinical patient subsets reviewed. In patients after infarction, the largest of the three subgroups, exercise-induced S-T segment elevation usually appears in leads with Q waves, is more common after anterior myocardial infarction and implies underlying akinetic or dyskinetic wall motion. Of patients with variant angina, 10 to 30 percent have during exercise S-T segment elevation that is most likely provoked by coronary arterial spasm. The natural history of variant angina is cyclic, and clinical observations and laboratory findings are dependent on particular phases in the disease process and treatment. Finally, 0.2 to 1.7 percent of symptomatic patiënts without infarction or variant angina have exercise-induced S-T segment elevation. Although most of the latter have fixed high grade coronary arterial stenoses at angiography, the exact pathogenetic mechanism of S-T segment shift in this patient group is not yet fully understood.