The ECG manifestations of unstable angina are transient ST segment depression, ST segment elevation and less frequently, T wave changes.” What is the role of the 12-lead ECG in patients with unstable angina? First, patients in whom episodes of chest pain is not associated with ECG changes seem to have less severe coronary artery disease than those with ECG changes. Second, according to some studies, patients with ST segment elevation have less extensive coronary artery disease in comparison to patients with ST segment depression. This finding could explain the higher mortality in the latter. Third, patients with ST segment elevation are more prone to coronary spasm and life-threatening arrhythmias than subjects with ST segment depression.* Fourth, the incidence of AMI during the initial hospitalization in patients with ST segment elevation and depression is 12 to 25 and 5 to 7 percent respectively.” The early survival rate is high in both groups (>95 percent). birth control pills
The third ECG manifestation of unstable angina is symmetrical T wave inversion or pseudonormalization of negative T waves. The incidence of T wave changes in unstable angina is between 3 and 16 percent. Because the T waves are influenced by many cardiac and extracardiac factors, it is important to correlate T wave changes with symptoms and other evidence of coronary artery disease. Haines et al compared patients who had unstable angina with and without T wave inversion. As expected, patients with anterior T wave changes had a higher incidence of significant coronary artery disease, AMI, and death in comparison to those with a normal ECG.