An exaggerated blood pressure (BP) response to maximal exercise is an independent risk factor for cardiovascular events and mortality. In people with hypertension, it is unclear if treating BP to guideline levels normalises the rise in BP during exercise, which is mediated in part by the metaboreflex. The main aim of this thesis was to assess whether adequate control of BP with anti-hypertensive medication normalises the exaggerated pressor response to exercise that is well established in untreated hypertension. It was hypothesised that treatments that reduce metaboreflex hyperreflexia would lower the BP response to maximal exercise. The BP response to exercise was assessed during an incremental exercise test to peak oxygen consumption (V̇O2 peak) on a cycle ergometer. To assess the BP response to metaboreflex isolation, post-exercise ischemia following isometric handgrip exercise was used. The first main finding of this thesis was that patients with treated-controlled, uncontrolled and untreated hypertension had an exaggerated BP response to exercise and metaboreflex isolation compared to age matched healthy controls. Secondly, the metaboreflex remains predictive of the peak BP response to incremental exercise when accounting for other known risk factors, including measures of central and peripheral arterial stiffness (aortic pulse pressure & pulse wave velocity), age and daytime ambulatory peripheral systolic BP. Finally, because the metaboreflex hyperreflexia depends on normal blood flow responses to exercise, an aim of this thesis was to improve nitric oxide bioavailability with chronic dietary nitrates. Despite improved levels of plasma nitrates in patients with treated-controlled hypertension, dietary nitrate supplementation had no impact on the maximal BP response to exercise or metaboreflex isolation compared to a placebo. Future research will need to assess alternative therapies to reduce exercise BP in patients with treated-controlled hypertension. This research will hopefully reduce the heightened cardiovascular risk in this population.
|Date of Award||23 Jan 2019|
- The University of Bristol
|Supervisor||Julian Paton (Supervisor) & Emma C J Hart (Supervisor)|