Heart rate variability and heart rate turbulence in patients with type 2 diabetes mellitus with versus without cardiac autonomic neuropathy.

Cardiac autonomic neuropathy (CAN) is an important complication of diabetes mellitus (DM) and confers an increased cardiovascular risk. The aim of this study was to disclose the place of heart rate (HR) variability and HR turbulence for the detection of CAN in patients with type 2 DM and no obvious heart disease. Ninety patients who were <75 years old and had type 2 DM for >/=2 years were studied. CAN was diagnosed with a battery of cardiovascular reflex tests and the degree of neuropathic involvement was graded by the Ewing score. Time-domain HR variability and HR turbulence parameters were assessed on 24-hour digital Holter recordings. Thirty-five patients were found to have CAN. The clinical characteristics of patients with and without CAN were similar, except that the mean duration of DM and the number of patients using insulin were significantly increased in the group with CAN. All time-domain HR variability parameters were significantly lower in the group with CAN. Of the 2 HR turbulence parameters studied, turbulence onset was similar but turbulence slope was significantly lower in the group with CAN. The Ewing score significantly correlated negatively with all HR variability parameters and turbulence slope, and among all, turbulence slope was the most strongly correlated (r = -0.617, p <0.01). Receiver-operating characteristics analysis revealed a sensitivity of 97% and a specificity of 71% at a turbulence slope cut-off value of 3.32 for the detection of CAN. In conclusion, time-domain HR variability and HR turbulence parameters, except turbulence, onset were found to be significantly depressed in patients with type 2 DM and CAN. Decreases in all these parameters were found to correlate significantly with degree of neuropathic involvement. The most strongly correlated parameter, turbulence slope, was found to be highly sensitive and specific for the detection of CAN at a cut-off value of 3.32.