PREVALENCE OF CARDIOVASCULAR AUTONOMIC DYSFUNCTION ASSESSED BY SPECTRAL-ANALYSIS AND STANDARD-TESTS OF HEART-RATE VARIATION IN NEWLY DIAGNOSED IDDM PATIENTS

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.