The prognostic importance of asymptomatic ischemic episodes in patients with unstable angina pectoris

Unstable angina pectoris is a high-risk ischemic disease which is characterized by recent onset of angina, a change in preexisting stable angina pattern or the occurrence of angina at rest. In a study of 70 patients with unstable angina on treatment with a triple drug regimen of nitrates, propranolol and nifedipine, 37 patients (53%) had 205 ischemic episodes, 90% of which were asymptomatic. 33 patients (47%) had no changes in the ST-segments. Between the two groups, there were no significant differences with respect to risk factors, medical treatment or coronary angiographic findings. Only the resting ejection fraction in the former group was slightly but significantly lower than in the latter group. At one month of follow-up seven patients had developed myocardial infarction, six of whom were in the group with silent ischemia. In 13 patients, due to inadequate success of medical treatment, bypass surgery or PTCA was performed; ten of these were from the group with silent ischemia. Of patients with silent ischemia, those with episodes totaling more than 60 minutes per 24 hours had the worst outcome. Multivariate analysis showed that, with respect to prognosis, the most important parameter was silent ischemia followed by angina pectoris.