Detection of exercise-induced silent ischemia and the sequence of ischemic events in coronary artery disease by radionuclide ambulatory ventricular function monitoring.

Twenty-seven patients with stable coronary artery disease were continuously monitored with an ambulatory radionuclide ventricular function monitor (VEST) during exercise to determine the prevalence of silent ischemia and the temporal sequence of events during ischemic episodes. Exercise-induced ejection fraction abnormality was considered a < 6% increase in the control value lasting for more than 60 sec. Patients performed exercise for 424 +/- 111 sec during VEST recording. Seventeen exercise-induced ejection fraction abnormalities were observed in 17 patients, of which eight (47%) were silent electrocardiographically and 12 (71%) were silent symptomatically. In all of the patients, exercise-induced ischemia occurred in a temporal sequence of ejection fraction abnormalities, ST depressions and then symptoms. In nine patients with ejection fraction and ST abnormalities, ejection fraction abnormalities occurred earlier (199 +/- 87 sec) than ST depressions (321 +/- 117 sec; p < 0.01). In five patients with symptoms (399 +/- 151 sec), the sequence was ejection fraction abnormalities (205 +/- 64 sec; P < 0.05) followed by ST depressions (266 +/- 101 sec; P < 0.05) and symptoms (399 +/- 151 sec; P < 0.01). After termination of exercise, ejection fraction (49 +/- 12 sec) recovered sooner than symptoms (102 +/- 27 sec; p < 0.01) or ST abnormalities (191 +/- 96 sec; p < 0.01). Thus, hemodynamic monitoring by VEST may be helpful in detecting ischemic episodes in coronary artery disease which remain electrocardiographically or symptomatically silent. Furthermore, exercise-stress induces a cascade of temporal changes in ischemic events which may be helpful in understanding the pathophysiology of ischemia.