Clinical Implications of Silent Versus Symptomatic Exercise-Induced Myocardial Ischemi in Patients With Stable Coronary Disease

Objectives. This study was undertaken to better understand the functional and prognostic significance of silent relative to symptomatic ischemia. Background. Previous studies have reached conflicting conclusions as to whether painless ischemi identified during noninvasive cardiac testing is related to lesser extent of myocardial ischemi or different prognosis than ischemi accompanied by angina, or both. Methods. Nine hundred thirty-six clinically stable patients 1 to 6 months after an acute coronary event, either myocardial infarction or unstable angina, underwent ambulatory monitoring, exercise treadmill testing and stress thallium-201 scintigraphy. They were then followed up prospectively for mean of 23 months for recurrent cardiac events (cardiac death, nonfatal myocardial infarction or unstable angina). Results. Compared with patients with symptomatic ischemi during testing (n = 125), those with silent ischemi (n = 378) demonstrated less severe and extensive reversible defects on stress thallium scintigraphy (p = 0.0008), less functional impairment during treadmill testing manifested by longer exercise duration (640 ± 173 vs. 529 ± 190 s, p = 0.002) and longer time to ST segment depression (530 ± 215 vs. 419 ± 205 s, p = 0.0001) and less frequent ST segment depression during ambulatory monitoring (9% vs. 19%, p = 0.005). Patients with symptomatic ischemi had significantly (p = 0.004) increased number of subsequent recurrent cardiac events (28.8%) versus those with silent (18.0%) or no (17.3%) ischemia. Adverse outcomes were especially concentrated in the subgroup with symptomatic ischemi and poor exercise tolerance. The difference in cardiac event rates between patients with silent versus symptomatic ischemi persisted after adjustment for baseline clinical characteristics by Cox regression analysis. Conclusions. Patients with painless ischemi during exercise testing 1 to 6 months after recovery from coronary event have less jeopardized ischemic myocardium and fewer recurrent cardiac events than patients with symptomatic ischemia.