Prognostic implications of transient--predominantly silent--ischaemia in patients with unstable angina pectoris.

The occurrence of unstable angina pectoris, despite medical treatment, is generally regarded as an ominous prognostic sign and an indication for invasive diagnosis and revascularization. We investigated 38 consecutive patients with severe unstable angina with a mean of 2.5 days of continuous two-channel, frequency modulated Holter monitoring for ST segment analysis. In 16 patients, transient ischaemic episodes (more than 0.1 mV lasting more than 1 min) occurred despite maximal medical treatment: 82% of the episodes were silent. Compared to the 22 patients without ischaemic episodes there were no significant differences in prevalence of risk factors, numbers of vessels diseased (69% vs. 74% triple-vessel disease) or ejection fraction (54 +/- 15% vs. 53 +/- 16%). The 30-day prognosis, however, varied: of 16 patients with ischaemic episodes, 14 (88%) had a subsequent cardiac event (death, AMI, PTCA or CABG) compared to only 10 of 22 patients (45%) without ischaemic episodes (P less than 0.02 for all events, P less than 0.1 for death/AMI only). Transient ischaemic episodes, predominantly silent, are frequent in patients with severe unstable angina. Objective evidence of ongoing ischaemia despite medical treatment has a guarded short-term prognosis. 'Stabilization' of unstable angina may be incomplete as long as transient ischaemia at rest can still be detected.