P5.09 INCREASED SYSTEMIC VASCULAR RESISTANCE DURING MODERATE EXERCISE INDEPENDENTLY PREDICTS A HYPERTENSIVE RESPONSE TO EXERCISE

Abstract

Background: A hypertensive response to exercise (HRE) at moderate intensity is an independent risk factor for cardiovascular events and mortality, but the underlying mechanisms are unknown. This study sought to determine the haemodynamic predictors of exercise blood pressure (BP) and an HRE. Methods: Study sample comprised 75 consecutive patients (aged 57±10 years; 73% male) who were free from coronary artery disease and had completed a clinically indicated exercise stress test. Participants were stratified according to systolic BP (SBP) at moderate exercise intensity (Bruce protocol stage 2) with the highest tertile (SBP ≥169 mmHg) defined as an HRE. All participants underwent comprehensive haemodynamic assessment at rest and during moderate exercise; including, brachial and central BP, aortic stiffness, cardiac output (CO) and systemic vascular resistance (SVR; using bioimpedance). Results: At rest, subjects with HRE had higher body mass index (BMI), triglycerides, aortic stiffness, brachial and central BP compared with normal exercise BP responders (p<0.05 for all), but no difference in resting SVR (p>0.05). During exercise, subjects with HRE had normal CO but significantly increased SVR (p=0.033) and, of all variables measured, this had the strongest correlation with exercise brachial and central SBP (r=0.527 and r=0.626 respectively; p<0.001). On multiple regression, exercise SVR (β=0.357, p=0.002) predicted exercise brachial SBP, independent of age, sex and BMI (Adjusted R2=0.399, p<0.001). Conclusions: Increased SVR during moderate exercise is independently related to exaggerated exercise SBP (HRE) in people undergoing clinically indicated stress testing. This suggests that abnormal peripheral vascular function may be a mechanism explaining exercise hypertension.