The Middle Cerebral Artery Flow Velocities during Head-Up Tilt Testing in Diabetic Patients with Autonomic Nervous System Dysfunction

Abstract

Background: The goal of this study was to examine the effects of diabetes mellitus on the trend of mean arterial velocity (v_m) in both middle cerebral arteries during head-up tilt (HUT). Methods: The study was performed in 20 patients, 9 females and 11 males (mean age 51 ± 12 years) with an average 17-year history of insulin-dependent diabetes mellitus type I or II and a dysfunction of the autonomic nervous system confirmed by cardiocirculatory tests [Valsalva maneuver, deep breathing test, handgrip test, orthostatic test and spectral analysis of heart rate (HR) variability], and 19 age-matched healthy volunteers, 9 females and 10 males (mean age 48 ± 6.8 years). v_m was measured by a transcranial Doppler monitoring system during a 5-min baseline period, followed by a 5-min HUT in the upright position (90°). Mean arterial blood pressure (MAP), HR and end-tidal CO₂ (Et-CO₂) were monitored concomitantly. Results: In healthy volunteers, v_m decreased stepwise during the first minute of HUT, reaching a minimum during the last 2 min of the test (v_m: basal 63.0 ± 11.7 cm/s, 1st min 57.6 ± 12.2 cm/s, 2nd min 55.9 ± 12.6 cm/s, 3rd min 53.4 ± 12.6 cm/s, 4th min 52.1 ± 12.7 cm/s, 5th min 51.3 ± 13.5 cm/s). In the supine position, v_m recovered and reached the resting v_m values. It declined gradually during HUT and less steeply in diabetic (v_m: basal 54.4 ± 10.1 cm/s, 1st min 51.96 ± 9.3 cm/s, 2nd min 50.7 ± 11.6 cm/s, 3rd min 50.5 ± 11.4 cm/s, 4th min 49.5 ± 10.7 cm/s, 5th min 48.8 ± 11.5 cm/s) than in healthy subjects. v_m differed significantly (p = 0.00) between rest and HUT in both groups. The differences in MAP, HR and Et-CO₂ during rest and HUT between the groups were not statistically significant (p ΔMAP = 0.36, p ΔHR = 0.86, p ΔEt-CO₂ = 0.97). The results of the analysis of variance of v_m for repeated measurements between the two groups of subjects were highly significant (p = 0.00). The model of linear regression analysis was significant (p = 0.007). Diabetes was significant in the model (p = 0.00), while ΔMAP, ΔHR and ΔEt-CO₂ were not. Conclusions: These findings may indicate that vasomotor responses during HUT testing are decreased in diabetic patients.