IMPAIRED ACTIVATION OF THE BAROREFLEX LOOP AS EARLY SIGN OF SYMPATHETIC DAMAGE IN DIABETICS WITH NORMAL HEART-RATE-VARIABILITY AT REST

The objective of the study was to define the impairment of sympathovag al balance in patients with diabetes mellitus (DM) and coronary heart disease (CHD) compared to healthy controls (HC) showing similar heart rate variability (HRV) at supine rest. 88 DM (41 m, 47 f; age 62 +/- 1 years; BMI 27.1 +/- 1.5 kg/m(2); HbA(1c) 7.9 +/- 0.4%), 49 CHD (27 m, 22 f; age 62 +/- 1 years; BMI 27.1 +/- 1.6 kg/m(2); HbA(1c) 5.2 +/- 0 .1%) and 16 HC (8 m, 8 f; age 59 +/- 1 years; BMI 26.4 +/- 0.5 kg/m(2) ; HbA(1c) 5.0 +/- 0.1%) were investigated. Time series of heart period duration (HPD) were obtained during 2 min deep breathing (6/min), 5 m in of supine rest and for 5 min at upright position using a RR memory device (BHL 6000, Baumann-Haldi Switzerland, modified ECG lead, 1 kHz) . Mean HPD, coefficient of Variation (CV), total power (TP) and integr al power in the HF (0.15 to 0.5 Hz), MF (0.05 to 0.15 Hz) and LF (0.01 5 to 0.05 Hz) frequency bands as well as (MF-HF)/(MF+HF) as spectral i ndex were calculated. As to be expected we found significantly lower v alues of CV, TP and HPD in DM compared to HC. The CV of HRV did not di ffer significantly between DM and CHD but TP and HPD of CHD patients w ere significantly higher in comparison to DM. Therefore, the deteriora tion of HRV was most pronounced in the DM group. For further analysis we calculated data of subjects with CV's in the upper quartile (greate r than or equal to 3.52) of the CV at supine rest. The aim of this pro cedure was to compare subjects with similar high HRV at supine rest. W ith this method we obtained from all subjects 12 HC, 11 DM and 12 CHD. These DM had a significant decrease of CV, TP and the integral power at the HF frequency band during active orthostasis compared to HC and CHD. The spectral index increased significantly during standing in HC and CHD but was unchanged in DM. These changes were accompanied by a n early similar increase of HRV during deep breathing. In conclusion, DM with normal reaction to deep breathing did not activate the sympathet ic baroreflex loop during active orthostasis. This could be an early s ign of sympathetic dysfunction in DM with normal HRV at supine rest.