Therapeutic rationale for the management of silent ischemia

Prognostic data on the importance of silent ischemia is lacking. Preliminary reports suggest that ambulatory electrocardiographic monitoring provides additional information not contained in the exercise test, but it is still unclear whether silent ischemia is a marker of subsequent events or is responsible for their development. Recent investigations also suggest that intermittent episodes of ischemia may cause myocardial necrosis. Drugs that are effective in the treatment of angina are also effective in the treatment of silent ischemia, but their value in terms of long-term morbidity and mortality is unclear. Recently, the circadian distribution of silent ischemia has been reported in 150 patients off therapy, in 33 receiving nifedipine, and in 41 receiving atenolol. Most ischemic episodes off therapy occurred between 7:30 AM and 7:30 PM with a peak in the morning and a lesser peak in the evening. Nifedipine did not alter the circadian pattern of ischemic episodes; atenolol abolished the morning peak, the peak incidence of ischemia then occurring in the evening. This circadian distribution of ischemic episodes and the observed changes with treatment resemble the reported circadian variations of acute myocardial infarction and sudden death. Large multicenter studies are now being performed to determine the effects of treatment on silent ischemia and how this treatment may influence outcome. Until such studies have been completed, it is not possible to clearly define the indication for drug therapy in the management of silent ischemia.