Exertional myocardial ischemia in diabetes: a quantitative analysis of anginal perceptual threshold and the influence of autonomic function.

Patients with diabetes are prone to silent myocardial infarction and silent exertional ischemia. Although the mechanism is not clear, it may reflect a specific impairment of the sensory innervation of the heart. To test this hypothesis, anginal perceptual threshold was measured in 32 diabetic patients and 36 nondiabetic control patients, all of whom had typical exertional angina. Anginal perceptual threshold was defined as the time from onset of 0.1 mV ST depression to the onset of chest pain during treadmill stress electrocardiography. Although ST depression occurred earlier in the diabetic than in the nondiabetic group (111 +/- 82 versus 216 +/- 162 s, p less than 0.005), the anginal perceptual threshold in the diabetic group was delayed by a mean of 86 s (149 +/- 76 versus 63 +/- 59 s, p less than 0.001), with 95% confidence intervals of 53 to 119 s. Autonomic function tests were abnormal in the diabetic group, and in both groups regression analyses (using a third order polynomial) showed marked prolongations of anginal perceptual threshold as the heart rate responses to the Valsalva maneuver decreased to below the normal range (r = 0.5, p less than 0.001). There was a similar though less pronounced relation between anginal perceptual threshold and the heart rate responses to deep breathing (r = 0.3, p less than 0.02). These data suggest that prolongation of the anginal perceptual threshold may be caused by autonomic neuropathy involving the sensory innervation of the heart. To test sensory function, median nerve conduction studies were performed in 19 patients (10 diabetic and 9 nondiabetic).(ABSTRACT TRUNCATED AT 250 WORDS)