Abstract
Heart rate (HR) variation tests are all considered to be mainly affected by parasympathicus. However, diabetic patients sometimes show normal HR variation on standing, although respiratory HR variations are remarkably decreased. This study was aimed at clarifying the reason for this discrepancy. Eight healthy subjects and six diabetic patients with autonomic neuropathy were used for the HR variation tests, which were performed in the supine resting position and during deep breathing (respiratory HR variations) and on standing (orthostatic tachycardia: JHR) by using atropine and propranolol. The results in both healthy subjects and diabetic patients showed that: 1) After the administration of atropine (40μg/kg, IV), the respiratory HR variations were almost completely abolished, whereas the decrease in ΔHR was insignificant. With additional propranolol (10mg, IV), ΔHR was significantly reduced as compared with that subsequent to atropine 2) Propranolol alone did not affect the respiratory HR variations, whereas JHR was significantly reduced. We conclude that the respiratory HR variations are prediominantly affected by the parasympathetic nervous system and the orthostatic tachycardia is influenced by both the parasympathetic and sympathetic nervous systems, particularly by the latter. These HR variation tests are valuable for the early detection of the cardiac parasympathetic or sympathetic damage in diabetic patients.
