Autonomic cardiovascular changes during reactive hyperemia.

PURPOSE: The objective of this study was to assess the variations in cardiovascular autonomic modulation during reactive hyperemia in diabetic patients with and without cardiovascular autonomic neuropathy (CAN). METHODS: The study subjects were 35 patients with T2DM without macrovascular complications of diabetes and 40 age and sex matched healthy subjects as the control group. Electrocardiogram and photoplethysmography recordings were performed at rest and during a reactive hyperemia test, which consisted of a 5-min arterial occlusion followed by release. Autonomic nervous system function was evaluated using heart rate variability analysis (time-frequency methods) and the sympathetic skin response. RESULTS: Healthy subjects showed a significant increase in low-frequency (LF) power immediately after vascular release, with an average latency of 339.64 ± 53.86 ms and amplitude of 3467.41 ± 2333.68 ms2. In diabetic patients with CAN, the response was faster but less intense (latency: 300.00 ± 20.22 ms, amplitude: 907.15 ± 2688.0 ms2). Diabetic patients without CAN showed a similar latency (300.06 ± 37.64 ms) but the amplitude is overall the lowest (505.73 ± 489.37 ms2). CONCLUSIONS: The reactive hyperemia test reveals an alteration in the temporal dynamics of autonomic activity, as reflected by the low-frequency component in heart rate variability analysis, in diabetic patients. These patients exhibit a reduced response amplitude and a faster or reactive response, especially those with cardiovascular autonomic neuropathy, suggesting altered autonomic modulation that could serve as an early marker of autonomic dysfunction.