Correlation of altered Q-T interval and sympathetic nervous system dysfunction in diabetic autonomic neuropathy.

We examined the relationship between the Q-T interval and autonomic dysfunction in 74 diabetic patients and age-matched controls. The expected Q-T interval was standardized as a function of the R-R interval in 646 healthy controls, and the delta Q-T defined as the difference from the expected value. Propranolol increased delta Q-T, confirming this as a parameter of autonomic function. No relationship between delta Q-T and duration of disease, glucose control, retinopathy or proteinuria was observed. However, significant correlations were found between the delta Q-T and delay of nerve conduction velocity, orthostatic hypotension, altered Valsalva ratio, abnormal Valsalva overshoot, cold pressor response, decreased norepinephrine concentration and sympathetic function score in diabetic patients.