Cardiac autonomic balance and QT dispersion during head-up tilt testing in diabetics with and without sensory neuropathy.

BACKGROUND: Cardiovascular autonomic dysfunction is associated with higher mortality in diabetics. However, detection methods of early cardiac diabetic dysautonomia, and its correlation with severity of sensory neuropathy, have not been described.
METHODS: We analyzed the heart rate variability (HRV) by spectral analysis and QT dispersion in 23 diabetics with and without sensory neuropathy, and in 5 age-matched controls, in the supine position and during head-up tilt testing (HUT). Diabetics were divided into 3 groups according to the degree of sensory neuropathy.
RESULTS: In the spectral analysis of HRV, the high frequency components in the supine position decreased as a function of severity of the neuropathy. High frequency in diabetics was significantly decreased in the supine position, even in absence of sensory neuropathy. The low/high frequency ratio (L/H) in the supine position was similar among controls and the 3 patient groups. L/H in diabetics with moderate or severe neuropathy did not increase from the supine to the upright position. Baseline QT dispersion increased proportionally to the severity of sensory neuropathy and, in patients without apparent sensory neuropathy, QT dispersion increased significantly during HUT.
CONCLUSIONS: The spectral analysis of HRV and measurements of QT dispersion, before and during HUT, were reliable detection methods of early abnormalities in autonomic balance and may predict a risk of sudden cardiac death in diabetics.