Vagal control of heart rate in obese non-insulin dependent diabetes mellitus patients

Abstract

The aim of study was to analyse the vagal control of heart rate in non-insulin dependent diabetes mellitus (NIDDM) patients with different body mass. Age and gender matched NIDDM patients (men, 61±1.8 yr, Hb A1c 8.1±0.9%,) were divided in two groups according to the body mass index, with overweight (n=14; BMI>30 kg/m2) and without overweight (n=17; BMI<25 kg/m2). Beat-to-beat HR and finger mean arterial pressure were monitored noninvasively. The carotid baroreceptors were stimulated applying neck suction (-60 mm Hg, for 5s) 6 times at rest and with 15s intervals during handgrip for 60 s with force 50% of maximal voluntary contraction. HbA1c was significantly higher in obese patients (9.6±0.2 vs 7.7±0.6%; p<0.05). Finger mean arterial pressure was increased (109±2.9 vs 95±2.7 mm Hg; p<0.05), heart rate didn't differ significantly, but bradycardic reaction (1.2±0.6 vs 2.7±0.8 bpm; p<0.05) to baroreflex activation was reduced in NIDDM patients with overweight. The amplitude of pressor reaction (41±4 vs 30±2.6 mm Hg; p<0.05) was decreased in patients with overweight. Although heart rate (73±2.5 vs 78±3.3 bpm; NS) didn't differ significantly at rest in analysed groups, the amplitude of heart rate acceleration (23±2.7 vs 11 ±1.7 bpm; p<0.05) at 60th s of handgrip was decreased in obese patients and heart rate non-linear acceleration trajectory was altered, especially the rapid component of the curve during the first 10 s of exercise which is connected with reduction of cardiac vagal tone. The bradycardic reaction to baroreflex activation progressively decreased during whole static exercise in patients without overweight, but in obese patients it already disappeared in the first 15 s of handgrip. The present data show that vagal control of heart rate was altered in obese NIDDM patients, which probably is related with worse glycaemic control.