Incomplete recovery of cerebral blood flow dynamics in sufficiently treated high blood pressure

Objective: Whether cerebrovascular regulation is different in patients with controlled high blood pressure (HBP) with and without small vessel disease (SVD). Methods: Sixty-seven healthy controls (mean age +/- SD, 45 +/- 16 years; 30 women, 37 men) and 40 patients (mean age, 64 +/- 13 years; 14 women, 26 men) with HBP and different stages of SVD, underwent simultaneous recordings of the spontaneous fluctuations of BP, blood flow velocity (CBFV) in both middle cerebral arteries (MCA), and of end-tidal CO2 (ETCO2). Coherence and transfer function gain and phase between BP and CBFV were assessed in the frequency ranges of VLF (0.02-0.07 Hz), low frequency (0.07-0.15), and high frequency (> 0.15). BP SD indicated BP variability (BPV). Results: In controls (BP, 86 +/- 13 mmHg; ETCO2, 39 +/- 4mmHg; BPV, 15 +/- 6 mmHg), gain, phase and coherence were not age-dependent in simple or a multiple regression models. BPV correlated significantly in both MCAs with gain in low frequency and high frequency, and with phase in VLF and high frequency. In patients (BP, 91 +/- 16 mmHg, ETCO2, 39 +/- 4 mmHg, BPV 18 +/- 5 mmHg), only gain showed some differences between different SVD groups. Comparing all patients with 25 controls of similar age and sex, patients exhibited significantly (P< 0.05-P<0.005): increased coherence and gain in VLF, decreased phase in VLF and low frequency, correlations between BPV with phase in low frequency (left) and with gain in VLF (left) and in high frequency (left and right). Conclusion: Phase seems an age independent autoregulatory index. In controlled HBP, CBF regulation is degraded at longlasting CBF changes; BPV effects lose their physiological bilateral distribution.