Abstract
Heart rate (HR) variations-in the supine position, on deep breathing and on standing-were measured in 162 healthy subjects and 168 diabetic patients in order to establish the criteria for the normal range for the diagnosis of autonomic neuropathy and to compare those three methods.
HR variations were measured by Goto's instantaneous-HR-change continuous recorder. As indices of autonomic neuropathy, the standard deviation of the HR in 150 consecutive HR at rest (SD of HR), the mean difference between maximal and minimal HR during deep breathing (I-E difference) and the HR increase on standing (δHRmax) were determined.
In healthy subjects, the values for each test declined with age and the date showed positively skewed distributions. Log-transformed data fitted the linear regression well. The 90% confidence limits were calculated for the normal range and the values below normal were defined as abnormal. The lowest normal values of the SD of HR were 2.07, 1.36, 0.89 beats/min; of the I-E difference, 14, 9, 6 beats/min; and of the δHRmax, 17, 14, 11 beats/min, in 20 y.o., 40 y.o., 60 y.o., respectively.
In diabetics, the incidence of abnormal response was 19% in the SD of HR, 38% in the I-E difference and 22% in the δHRmax. The I-E difference was considered to be the most sensitive index for detecting the autonomic neuropathy. The δHRmax was considered to be able to detect the different mechanisms of neural reflexes because of the poor correlation between the δHRmax and the SD of HR, or the I-E difference.
The present studies suggested, therefore, that two HR variations, on deep breathing and on standing, should be measured at the same time to evaluate the autonomic neuropathy synthetically.
