Wave reflections, arterial stiffness, heart rate variability and orthostatic hypotension.

Increased arterial stiffness and wave reflections are independently associated with orthostatic hypotension (OH). This study investigated whether heart rate variability (HRV) is also involved in the modulation of orthostatic blood pressure (BP) change. A total of 429 subjects (65.1 ± 16.4 years, 77.4% men) were enrolled in this study. OH was defined as a ⩾ 20 mm Hg decrease in brachial systolic blood pressure (SBP) or a ⩾ 10 mm Hg diastolic blood pressure (DBP) decrease upon standing. Measurements of carotid-femoral pulse wave velocity (cf-PWV) and the amplitude of the reflected pressure wave from a decomposed carotid pressure wave (Pb) were obtained by carotid tonometry in the supine position. The power spectrum from a 5-min recording of an electrocardiogram at rest was analyzed to provide components in the high frequency (HF) and low frequency (LF) ranges. Subjects with OH (n = 59, 13.8%) had significantly higher cf-PWV and Pb and significantly lower LogHF and LogLF than those without OH (n = 370). The cf-PWV, Pb, LogHF and LogLF were significantly associated with postural SBP and DBP changes. Furthermore, cf-PWV but not Pb was significantly associated with LogHF and LogLF. Multivariate analysis showed that Pb (odds ratio (OR) per 1 s.d. 1.65, 95% confidence interval (CI) 1.282-2.137; P = 0.003) and LogHF (OR 0.628, 95% CI 0.459-0.860, P = 0.004), but not cf-PWV (OR 1.279, 95% CI 0.932-1.755, P = 0.128), were significant independent determinants of OH. Increased wave reflections may predispose OH independently of arterial stiffness and HRV. In contrast, increased arterial stiffness may cause OH through the modulation of HRV.