Evidence of defective cardiovascular regulation in insulin-dependent diabetic patients without clinical autonomic dysfunction

Abstract (1) Autonomic dysfunction is a well recognised complication of diabetes mellitus and early detection may allow therapeutic manoeuvres to reduce the associated mortality and morbidity. We sought to identify early cardiovascular autonomic neuropathy using spectral analysis of heart rate and systolic blood pressure variability. (2) Thirty patients with Type 1 (insulin-dependent) diabetes mellitus (DM) and 30 matched control subjects were studied. In addition to standard tests of autonomic function, heart rate and systolic blood pressure variability were assessed using power spectral analysis. From the frequency domain analysis of systolic blood pressure and R–R interval, the overall gain of baroreflex mechanisms was assessed. (3) Standard tests of autonomic function were normal in both groups. Total spectral power of R–R interval was reduced in the Type 1 DM group for low-frequency (473±63 vs. 747±78 ms 2 , mean±S.E.M., P =0.002) and high-frequency bands (125±13 vs. 459±90 ms 2 , P 2 , P P =0.002), implying a relative sympathetic predominance. When absolute powers were expressed in normalised units, these differences persisted. There were significant reductions in baroreceptor-cardiac reflex sensitivity in Type 1 DM patients compared to controls while supine (9.7±0.7 vs. 18.5±1.7 ms/mmHg, P P