Abstract
The R-R interval on electrocardiograms was analyzed as an indicator of the function of the autonomic nervous system. The records were taken after 2: 00 p.m., at a time of stabilized heart rate, and were analyzed with a signal processor and dynamic cardioscanner.
The variation in R-R interval during deep breathing as expressed by the standard deviation of the mean value of the interval was 41.8 ± 2.1 msec (M±SE) in 163 patients showing a diabetic glucose tolerance test. This was significantly shorter (p<0.001) than the value for 245 individuals with a normal glucose tolerance test (58. 2±1.6 msec) and that for 176 subjects with a borderline glucose tolerance test (58.4 ±2.4 msec). The ratio of the standard deviations of the R-R intervals in deep breathing and in normal breathing was also signigcantly different (p<0.001) at 2.12 ±0.07, 2.79±0.07, and 2.80±0.09, respectively. Similar results were obtained after selecting subjects of comparable ages within the 3 groups. Histograms for the R-R interval in diabetic patients were sharper and frequently polyphasic compared with a smooth rounded peak in normal individuals.
Among diabetic patients, the standard deviation and ratios were significantly smaller (p<O.001) in patients with identifiable symptoms of the peripheral or autonomic nervous system than those without such symptoms, and in patients with a duration of diabetes in excess of 10 yr than those with a shorter history.
The above results indicate disturbance of the autonomic nerve control of heart rate in patients with diabetes mellitus, and suggest that analyses of the R-R interval can provide a valuable objective indicator of the function of the autonomic nervous system.
