Background: It has been known that impairment in vagal control of heart rate in diabetic autonomic neuropathy is frequent and leads to diminished spontaneous variation of heart rate at rest or with deep inspiration. And there are many simple non-invasive maneuvers designed to assess the cardiovascular autonomic neuropathy. In this study, 24-hour ambulatory heart rate monitoring was performed in patients with diabetic autonomic neuropathy to investigate the changes in heart rate during daily acitvities.
Method: To assess autonomic neuropathy, we measured the beat-to-beat variation(BBV) in heart rate during deep breathing in 57 NIDDM patients. The value of difference between the maximum and minimum heart rate lower than 10 beats/min was considered as abnormal(group Ⅰ, n=45), and higher than 10 beats/min as normal(group Ⅱ, n= 12). 24-hour ambulatory heart rate monitoring was carried out in 57 diabetic patients and 11 control subjects with normal daily activity. And changes in the heart rate and rhythm in group Ⅰ and Ⅱ were compared to those in normal subjects.
Resutts:
1) 24-hour mean heart rates were significantly higher in group Ⅰ(76.9±10.7 beats/min) and Ⅱ(76.2±11.1 beats/min) than in normal subjects(67.6±2.5beats/min)(p <0.01, p<0.05 respectively).
2) Maximum heart rates during 24 hour in diabetic groups were no significantly different from that in normal subjects, but minimum heart rates were sigificantly higher in group Ⅰ(56.3±18.4 beats/min) than in normal subjects(48.1±8.7 beats/min)(p <0.05).
3) The value of difference between maximum and minimum heart rates during 24 hour were 51.9±25.1, 61.3±25.5, and 74.6±14.9 beats/min in group Ⅰ, Ⅱ, and normal, respectively, and the value was significantly higher in group Ⅰ than normal(p<0.01).
Conclusion: These results showed that 24-hour mean heart rate was higher in diabetic patients than in control subjects and suggested that 24-hour heart rate monitoring seems useful in the assessment of the cardiovascular autonomic neuropathy in diabetic patients with known or suspected autonomic failure.
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