Noninvasive exploration of cardiac autonomic neuropathy - Four reliable methods for diabetes?

OBJECTIVE - The purpose of this work was to assess relevant information tha t could be provided by various mathematical analyses of spontaneous blood p ressure (BP) and heart rate (HR) variabilities in diabetic cardiovascular n europathy. RESEARCH DESIGN AND METHODS - There were 10 healthy volunteers and 11 diabe tic subjects included in the study. Diabetic patients were selected for non symptomatic orthostatic hypotension in an assessment of their cardiovascula r autonomic impairment. Cardiac autonomic function was scored according to Ewing's methodology adapted to the use of a Finapres device. The spontaneou s beat-to-beat BP and HR variabilities were then analyzed on a I-h recordin g in supine subjects. The global variabilities were assessed by standard de viation, fractal dimension, and spectral power. The cardiac baroreflex func tion was estimated by cross-spectral sequences and Z analyses. RESULTS - In diabetic patients, Ewing's scores ranged from 1 to 4.5, confir ming cardiovascular autonomic dysfunction. In these diabetic patients, glob al indices of variabilities Here consistently lower than in healthy subject s. Furthermore, some of them (standard deviation and fractal dimension of H R, spectral power of systolic blood pressure and HR) were significantly cor related with the Ewing's scores. The Z methods and the spectral analysis fo und that the cardiac baroreflex was less effective in diabetic subjects. Ho wever, the baroreflex sensitivity could not be reliably assessed in all the patients. The sequence method pointed out a decreased number of baroreflex sequences in diabetic subjects that was correlated to the Ewing's score. CONCLUSIONS - Indices of HR spontaneous beat-to-beat variability are consis tently related to the degree of cardiac autonomic dysfunction, according to Ewing's methodology. The Z method and spectral analysis confirmed that the cardiac baroreflex was impaired in diabetic patients. These methods might be clinically relevant for use in detecting incipient neuropathy in diabeti c patients.