Quantitative Evaluation of Diabetic Autonomic Neuropathy by Measuring Heart Rate Variations

Discrimination between Sympathetic and Parasympathetic Damage

Abstract

To analyze the regulatory mechanism of autonomic nerves on heart rate (HR) variations, pharmacological experiments were performed in 8 normal subjects.HR variations were measured with Goto's instantaneous-HR-change continuous recorder.As indices of HR variation, the standard deviation of HR in 150 consecutive HR in the supine position (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 evaluated. HR variations were recorded in three experiments before and after the administration of autonomic drugs.Exp. 1: during isoproterenol (Isop., 0.66 ug/min), the SD of HR and I-E difference were reduced compared with those during saline. Exp.2: afteradministration of atropine (At., 40μg/kg iv), the SD of HR and I-E difference were almost completely abolished. However, no significant difference in ΔHRmax was found compared to the control in spite of a reduction in ΔHRmax. With additional propranolol (Prop.10 mg iv)μHRmax was remarkably reduced. Exp.3: Prop. (10 mg iv) alone did not affect the SD of HR and I-E difference, but ΔHRmax was significantly reduced compared to thc control.
The present results demonstrate that the respiratory HR variations in the supine resting position were predominatly affected by parasympathetic function.On the other hand, the HR response to standing was affected by both sympathetic and parasympathetic function, particularly sympathetic function. By using these HR variation tests, it is considered possible to detect sympathetic or parasympathetic damage separately.