FACTORS INVOLVED IN CARDIAC AUTONOMIC NEUROPATHY IN DIABETIC-PATIENTS

The role cardiac autonomic neuropathy (CAN) plays in diabetes is not w ell known. The aim of this study was to identify the factors involved in CAN in diabetic patients. One hundred patients, 44 insulin-dependen t (IDDM) and 56 non-insulin-dependent (NIDDM), were investigated, usin g five standard tests. Three of these tests were for parasympathetic c ontrol (cardiac response to the lying-to-standing, deep breathing, and Valsalva tests), and the other two measured sympathetic control (test ing for orthostatic hypotension and evaluating heart and blood pressur e response to the handgrip test). Results were compared to those found in a series of 40 healthy volunteers. An age-adjusted comparison with the controls, showed that 34 patients had one abnormal parasympatheti c test, 23 had two, and 6 patients had three. Cardiac parasympathetic neuropathy was thus present in 63% of the patients. The handgrip test was completed by 84 diabetic patients. There was evidence of orthostat ic hypotension and/or an abnormal cardiac response to the handgrip in 15 of these patients, who all had a parasympathetic abnormality as wel l. There was no significant association between the type of diabetes a nd the presence of CAN. The duration of diabetes was significantly lon ger in patients with CAN (9.3 +/- 0.9 years) (p < 0.01) than in those with all three parasympathetic tests normal (5.8 +/- 0.9 years) (p < 0 .01). The HbA(1c) level was also higher in patients with CAN than in t hose with three normal parasympathetic tests (9.95 +/- 0.35% versus 8. 17 +/- 0.42%, p < 0.005). There was a significant association between the presence of retinopathy, observed by angiofluorography, and the pr esence of peripheral neuropathy confirmed by the electrophysiological investigation and the presence of CAN (p < 0.001). However,more than h alf the patients without retinopathy or nephropathy had CAN, and 11 of the 31 patients with a normal electrophysiological investigation also had CAN. Eighteen patients (6 IDDM) without retinopathy and nephropat hy, who had been diabetic for less than 2 years, also had CAN. This st udy shows that CAN occurs early and is frequently found in a populatio n of unselected diabetic patients. Metabolic factors may play an impor tant role in its occurrence. CAN is significantly associated with the presence of retinopathy, which suggests that an impairment of autonomi c peripheral blood flow control might be a contributing factor in the formation of microvascular lesions. (C) Elsevier Science Inc., 1997.