Heart-rate variability and cardiac autonomic function in diabetes.

Area of Science:

• Cardiology
• Diabetology
• Neurology

Background:

• Diabetes mellitus, particularly insulin-dependent type, is associated with autonomic neuropathy.
• Standard autonomic function tests may not always detect early-stage cardiac autonomic dysfunction.
• Heart-rate variability (HRV) analysis offers a non-invasive method to assess cardiac autonomic function.

Purpose of the Study:

• To evaluate cardiac autonomic function in diabetic subjects using 24-hour heart-rate variability (HRV) monitoring.
• To compare the sensitivity of 24-hour HRV with standard autonomic function tests in detecting vagal neuropathy in diabetes.

Main Methods:

• Twenty-four-hour ambulatory electrocardiography was used to record R-R intervals in 25 diabetic subjects and 11 controls.
• Heart-rate variability (HRV) was calculated using the standard deviation of successive R-R interval differences.
• Diabetic subjects were categorized into groups based on standard autonomic function tests: normal (group 1) and presence of vagal neuropathy (group 2).

Main Results:

• HRV was significantly reduced in both diabetic groups (group 1: 73 ± 9 ms; group 2: 65 ± 12 ms) compared to controls (138 ± 10 ms).
• Standard autonomic function tests failed to distinguish the subtle vagal dysfunction detected by HRV in group 1 diabetic subjects.
• 24-hour HRV measurement demonstrated a higher sensitivity in detecting cardiac autonomic dysfunction.

Conclusions:

• Twenty-four-hour HRV monitoring is a sensitive tool for detecting early cardiac autonomic dysfunction in patients with diabetes mellitus.
• This advanced HRV technique surpasses standard tests in identifying subtle autonomic changes, particularly vagal neuropathy.
• Routine use of 24-hour HRV could improve the early diagnosis and management of diabetic autonomic neuropathy.