Asymptomatic myocardial ischemia in diabetic patients

The recent recognition of the prevalence of asymptomatic ST-segment depression in patients with coronary artery disease demonstrates the poor sensitivity of using angina as a sign of myocardial ischemia. Possibly the greatest application of ambulatory ST-segment monitoring for the detection of asymptomatic ischemia is in diabetic patients. Coronary artery disease represents the ultimate cause of death in more than half of such patients and usually manifests itself prematurely at an advanced stage. The long-held clinical belief that infarction may be silent, or less painful, in patients with diabetes is supported by several retrospective studies (32 to 42 percent of diabetic patients lack angina at infarction, compared with only 6 to 15 percent of nondiabetic patients). Explanations for this observation have been remarkably deficient in the literature. One group has shown that in diabetic patients with painless infarction, the autonomic nerve fibers of the heart display typical lesions of autonomic neuropathy that may affect afferent sensory impulse transmission compared with those in several matched control groups. Except for a recent report from Italy, there are no data on the prevalence of asymptomatic ischemia in diabetic patients. There are obvious reasons to address this issue more comprehensively: first, given the high incidence of painless myocardial infarction, the frequency of asymptomatic ischemia may be very high; second, because the ability to evaluate patients with standard treadmill testing is limited in patients with peripheral vascular disease and diabetic neuropathy, ambulatory monitoring may be used on a more widespread basis; and third, given the higher than average incidences of sudden death and left ventricular dysfunction in diabetic patients compared with nondiabetic patients, ambulatory monitoring may represent a method of assessing the role of episodic ischemia in explaining these other cardiac events.