Increased pulse wave velocity in persons with spinal cord injury: the effect of the renin-angiotensin-aldosterone system.

Increased pulse wave velocity (PWV), a marker of cardiovascular disease (CVD), has been reported in otherwise healthy individuals with spinal cord injury (SCI) compared with age-matched uninjured controls. Due to decentralized descending sympathetic vascular control, individuals with injuries above T6 are prone to orthostatic hypotension and, as a result, depend on the renin-angiotensin-aldosterone system (RAAS) to maintain orthostatic blood pressure (BP). The purpose of this study was to determine resting PWV, a noninvasive surrogate of central arterial stiffness, in individuals with cervical (C4-T1; = 11) and thoracic (T6-T12; = 11) SCI, compared with age-matched controls (controls; = 11). Next, our aim was to describe group differences in BP, plasma norepinephrine (NE), and renin response to head-up tilt (HUT). Finally, we sought to determine the relationship between PWV and the orthostatic change in BP, NE, and the plasma renin during HUT among the groups. PWV was significantly increased in both cervical (8.81 ± 1.91 m/s) and thoracic (7.36 ± 1.58 m/s) SCI compared with the controls (5.53 ± 0.95 m/s; < 0.05). The change from supine to 60° HUT in BP and NE was significantly reduced and change in plasma renin was significantly increased in the cervical group compared with the thoracic and control groups. Group affiliation and change in plasma renin were significant predictors of PWV ( = 0.63, = 0.001). These data suggest that dependency on the RAAS for orthostatic BP maintenance may be associated with increased PWV and risk of CVD in the SCI population. Our novel findings suggest that increased arterial stiffness in individuals with SCI may be due to greater dependency on the RAAS to maintain hemodynamic stability during an orthostatic challenge. Asymptomatic orthostatic hypotension can occur in persons with SCI during transition from the supine to the seated position and during other upright activities of daily living; however, it is seldom addressed by clinicians.