SILENT-MYOCARDIAL-ISCHEMIA - ROLE OF SUBCLINICAL NEUROPATHY IN PATIENTS WITH AND WITHOUT DIABETES

Objectives. Silent myocardial ischemia is common in patients with diab etes. This study was designed to assess the role of subclinical autono mic impairment in diabetic patients with silent ischemia. Background. Studies have suggested that silent ischemia is more common in diabetic patients with microvascular complications, but this has not been a co nsistent finding. Methods. Twenty-two diabetic and 30 nondiabetic pati ents with proved coronary artery disease and a history of angina and i schemia on treadmill stress testing underwent clinical tests of autono mic function and measurement of 24-h heart rate variability. Diabetic patients with a history of microvascular complications were excluded. Results. Although all 52 patients manifested ischemia during treadmill testing, only 36 patients experienced angina (angina group), whereas 16 did not (silent ischemia group). Diabetic and nondiabetic patients were similar in age (59 +/- 1 Vs. 61 +/- 2 years, p = 0.56) and extent of coronary artery disease. However, clinical tests showed reduced pa rasympathetic function in the diabetic patients (Valsalva ratio 1.38 /- 0.07 vs. 1.60 +/- 0.06, p = 0.007). Patients in the silent ischemia group were more often diabetic (33% vs. 63%, p = 0.05) and had prolon ged time to ischemia on treadmill testing (200 +/- 20 vs. 271 +/- 20 s , p = 0.03). In addition, autonomic function was impaired in the silen t group (supine/standing heart rate ratio 1.15 +/- 0.02 vs. 1.05 +/- 0 .02, p = 0.002). Subgroup analysis showed that abnormalities of autono mic function were confined to the diabetic patients in the silent grou p. Conclusions. Despite the absence of overt microvascular complicatio ns, diabetic patients with silent exertional ischemia have evidence of significant autonomic impairment compared with findings in symptomati c patients. This difference is not seen in nondiabetic patients and in dicates that subclinical neuropathy is an important cause of silent is chemia in patients with diabetes.