Prevalence of Cardiovascular Autonomic Dysfunction Assessed by Spectral Analysis and Standard Tests of Heart-Rate Variation in Newly Diagnosed IDDM Patients

Abstract

Objective To determine the prevalence of cardiovascular autonomic nerve dysfunction in patients with newly diagnosed insulin-dependent diabetes mellitus (IDDM) compared with healthy nondiabetic subjects. Research Design and Methods A battery of cardiovascular reflex tests was performed in 130 newly diagnosed IDDM patients aged 12–40 yr at mean blood glucose levels of 7.2 mM after insulin had been administered for 3–39 days. Age-dependent lower limits of normal of these tests were defined at the 2.3 percentile in 120 nondiabetic subjects. Tests of heart-rate variation (HRV) included the coefficient of variation (C.V.) and the low-frequency (LF), midfrequency (MF), and high-frequency (HF) bands of spectral analysis at rest, HRV during deep breathing (C.V., expiratory-inspiratory ratio, and mean circular resultant), Valsalva ratio, and maximum/minimum 30:15 ratio. In addition, spectral analysis on standing, the change in systolic blood pressure to standing, and diastolic blood pressure response to sustained handgrip were determined in 50 patients. Results A significantly higher percentage of abnormal test responses in the diabetic group compared with the control group was noted for power spectrum in the LF band (7.3 vs. 0.8%, P < 0.05) and MF band (10.6 vs. 0%, P < 0.001) at rest and HF band on standing (10.0 vs. 0.9%, P < 0.05), maximum/minimum 30:15 ratio (25.4 vs. 5.0%, P < 0.001), and Valsalva ratio (17.5 vs. 4.2%, P < 0.001). There were no significant differences between both groups in regard to the remaining parameters. Ten (7.7%) diabetic patients but none of the nondiabetic subjects had cardiovascular autonomic neuropathy defined by the strict criterion of abnormal results in more than three of six tests (P < 0.001). In addition, 12 (9.2%) patients but only 2 (1.7%) control subjects had abnormal results in two of six tests (P < 0.01). Conclusions Cardiovascular autonomic nerve dysfunction is relatively common in newly diagnosed IDDM patients after correction of the initial metabolic imbalance. A combination of tests based on spectral and conventional analysis of HRV appears suitable for detection of early abnormalities in autonomic function in diabetes.