EARLY RECOGNITION OF AUTONOMIC DYSFUNCTION IN MICROALBUMINURIA - SIGNIFICANCE FOR CARDIOVASCULAR MORTALITY IN DIABETES-MELLITUS

The appearance of microalbuminuria in diabetic patients predicts devel opment of macroalbuminuria and coronary heart disease. Autonomic dysfu nction in ischaemic heart disease is related to an increased incidence of arrhythmic deaths. To assess sympathovagal balance in relation to microalbuminuria we performed 24-h spectral analysis of RR interval os cillations in 37 insulin-dependent diabetic patients. Patients were di vided according to urinary albumin excretion as normo-(< 20 mu g/min) (n = 12), micro-(> 20 and < 200 mu g/min) (n = 14) and macro-albuminur ia (> 200 mu g/min) (n = 11). None had symptoms or signs of ischaemic heart disease at clinical examination or during stress testing. Fourte en matched healthy subjects served as controls. Overall RR interval va riability was calculated as the 24-h standard deviation. The square ro ot of power of the low-frequency (0.04-0.15 Hz) and high-frequency (0. 15-0.40 Hz) component were considered indices of the sympathovagal int eraction and vagal function, respectively. Patients with micro and mac roalbuminuria had, compared to control subjects, significantly reduced 24-h standard deviation, a much smaller day/night difference in mean RR level and a significantly reduced amplitude of the low frequency an d high frequency oscillations, which were even more reduced in macroal buminuria. The differences in vagal function were also present after c orrection for mean RR level, and differences in physical training leve l and smoking. Insulin-dependent diabetic patients who develop microal buminuria have significantly impaired vagal function and abnormal symp athovagal interaction, which is further deranged in macroalbuminuria. This early autonomic dysfunction may later contribute to a increased r isk for sudden cardiac death.