Background: Cardiac autonomic neuropathy is a common complication of long-standing, type 1 diabetes and is associated with increased morbidity and mortality. Impaired heart rate variability is a sensitive and reproducible marker of cardiac autonomic neuropathy. We sought to examine the relationship between cardiac autonomic neuropathy as assessed by heart rate variability and overt nephropathy, with emphasis on the progression of renal dysfunction over 1 year.
Method: Baseline and 12 month clinical and biochemical characteristics, as well as autonomic function tests, were analyzed in 23, type 1 diabetic patients (mean age 37+/-10 years, 65% males), who were prospectively enrolled as a part of a multi-center investigation. In addition, ambulatory, 24-h, 3-channel electrocardiograms were recorded, and heart rate variability indices were assessed in the time and frequency domains over the same period.
Results: All heart rate variability indices were markedly decreased in our study population. On univariate analysis, heart rate variability was associated with creatinine clearance, and to a lesser extent, mean 24-h blood pressures and cholesterol. On multivariate analysis, only heart rate variability was a significant and independent predictor of abnormalities in creatinine clearance. Severe reduction in heart rate variability at baseline was also significantly associated with the further deterioration in renal function at 1 year.
Conclusion: Heart rate variability is significantly reduced in long-standing, type 1 diabetics with proteinuria or overt nephropathy. Marked abnormalities in heart rate variability are significantly associated with and predictive of progressive renal deterioration at 1 year. These findings may have implications for aggressive medical intervention to improve prognosis and survival in this population.