Objective: To assess the sensitivity of exercise induced heart rate (HR) and baroreceptor reflex (BR) chronotrope reaction and HR variability for an early detection of autonomic nervous system impairment in non-insulin dependent diabetes mellitus (NIDDM) patients with arterial hypertension.
Design and Methods: On 25 NIDDM pts (group A, 63±1.8 yrs. aged men, HbA1C 10.2±0.9%), 17 essential hypertension (EH) pts without glucose metabolism disturbances (group B, gender and age matched) and 20 controls (C) at rest and during handgrip (with force 50% of maximal for 60 s), beat-to-beat HR and finger mean arterial pressure (MAP) were monitored and bradycardic reaction to BR activation (by neck suction −60 mmHg) was analysed. HR variability by time and frequency domain analysis of ECG 512 R-R interval files was performed in supine and upright postures.
Results: Group A comparing to B and C was characterised by increased HR (81±2 vs.72±3 vs.70±3 bpm; P<0.05) and decreased bradycardic reaction to BR activation (1.95±0.3 vs. 4.9±0.9 vs.10±0.6 bpm; P<0.05). At 60th sec of handgrip MAP increase was similar in all groups but HR increase was reduced in group A vs. B vs.C (12±2 vs. 24±2 vs.18±2 bpm; P<0.05), but reaction to BR activation disappeared in group A and B, whereas in C remained in 32±11% of resting value. R-R interval variability in group A and B was diminished (P<0.01), but its decrease in upright position was less in group A than in C (108±12 vs. 254±21 ms; P<0.05), whereas the difference of increase in low-high frequency band ratio (LF:HF) was not significant in group A and B.
Conclusion: In patients with non-insulin dependent diabetes mellitus and hypertension, HR reaction to exercise and BR activation has an advantage over HR variability analysis to ascertain an early impairment of autonomic control of sinus node.