SPECTRAL ANALYSES OF R-R INTERVAL AND SYSTOLIC BLOOD-PRESSURE IN DIABETIC AUTONOMIC NEUROPATHY

We studied autonomic nervous system function using the principle of ma ximum entropy (ME) to perform spectral analyses of the R-R interval an d systolic blood pressure in 32 diabetic patients and 40 healthy contr ols. The R-R interval and systolic blood pressure were measured using a continuous, noninvasive monitoring system. The power spectra of both the R-R interval (RR) and systolic blood pressure (SYS) were obtained using ME and the areas of two frequency components were measured: a l ow- (LFC) and a high-frequency component (HFC). The RR-LFC, RR-HFC and SYS-LFC of diabetic patients were significantly smaller than those of healthy controls. The results of the spectral analyses in diabetic pa tients correlated with neither disease duration nor nephropathy, while the SYS-LFC showed significant correlations with both retinopathy and the delay in median motor nerve conduction velocity. In the mild auto nomic neuropathy group, the RR-LFC and SYS-LFC were not differ from th ose of healthy controls or patients without autonomic neuropathy. Howe ver, the RR-HFC was significantly smaller than that of healthy control s or patients without autonomic neuropathy. In the setting of mild dia betic autonomic neuropathy, it was suggested that cardiac parasympathe tic dysfunction preceded both alpha and beta sympathetic dysfunction.