Orthostatic Hypotension and Heart Rate Variability as Indicators of Cardiac Autonomic Neuropathy in Diabetes Mellitus

Aim: The aim of this study was to emphasize two different points in our work: 1) The well known importance of (subclinical) postural hypotension and reduced heart rate variability as (early) markers of autonomic neuropathy; 2) and the more controversial influence of diabetic control in their worsening. Methods: Two standard cardiovascular response tests (heart rate variability by respiration and orthostatic blood pressure changes) were carried out on 93 diabetic patients with prolonged QT interval in order to determine cardiac dysautonomy. QT segment duration was measured on electrocardiography recordings. Patients with HbA1c levels below 7 were considered as wellcontrolled diabetics. A cut off of 5 years was selected for the known duration of diabetes. The relations between cardiac autonomic neuropathy and diabetic control and the known duration of diabetes were determined. Results: The mean values for the known duration of diabetes and HbA1c level were 10±7.23 years and 9.5±2.3 mg/dl respectively. Median QTc differences, postural change in the systolic blood pressure, and changes of heart rate by respiration were 0.62 sec, 20 mmHg, and 6 beat/min, respectively. There was no difference in QTc values with respect to diabetes control but QTc values were significantly different with regard to the known duration of diabetes. Blood pressure variations with standing were significantly related to control as well as the known duration of diabetes. Variability of hearth rate with respiration on the other hand was significantly related to the duration but not to the control of diabetes. QTc showed a significant correlation with the known duration of diabetes, postural blood pressure changes, and heart rate variability with respiration. Conclusion: Clinician’s should be more alert for the signs of autonomic neuropathy, especially in patients with a history of diabetes for more than five years. Special attention should be given to postural blood pressure changes and heart rate variability with respiration.