P135 FITNESS INFLUENCES THE RELATIONSHIP BETWEEN EXERCISE BLOOD PRESSURE AND LEFT VENTRICULAR STRUCTURE: EVIDENCE FROM THE EXERCISE STRESS TEST COLLABORATION (EXERTION) STUDY

Background. A hypertensive response to exercise is associated with left ventricular (LV) remodelling, a principal sign of hypertensive heart disease. Fitness may modify this relationship, making clinical interpretation of peak exercise systolic blood pressure (SBP) challenging. This study examines the influence of fitness on the relationship between peak exercise SBP and LV structure. Methods. Cardiovascular structure and function (LV mass index (LVMI), LV relative wall thickness (RWT), cardiac output (CO) and total peripheral resistance (TPR)) were assessed at rest by echocardiography on 4,309 individuals (aged 58.6±12.7 years,52.0% male). SBP was measured at peak treadmill exercise, and fitness (exercise duration (minutes)) was grouped into thirds. Multiple regression analysis was conducted with fitness as an interaction term with peak exercise SBP, adjusted for age, sex, pre-exercise SBP, and cardiovascular disease (CVD) history. Results. Peak exercise SBP was similar across low (180±26.5mmHg), moderate (181±26.3mmHg) and high (182±24.5mmHg) fitness groups. Fitness modified the relationship between exercise SBP and LVMI; each 5mmHg increase in exercise SBP was associated with LVMI in moderate [0.27(0.10–0.43) and high [0.25(0.06–0.43)] fitness groups, which was not observed among those with low fitness [-0.05(-0.22–0.12)]. RWT increased with higher peak exercise SBP at all fitness levels (all p<0.001), with higher values among those with low fitness. Prevalence of LV concentric remodelling was highest in those with low fitness (29.9%) and lowest in those with high fitness (10.8%). A lower CO and higher TPR were observed in the low fitness group (7.5±2.5L/min and 14.3±5.1mmHg min/L) compared to those with high fitness (10.9±3.1L/min and 9.2±2.09mmHg min/L). Conclusion. Whilst a small effect, fitness modified the peak exercise SBP-LV structure relationship, such that for similar peak exercise SBP, those with low fitness exhibit a more adverse LV remodelling, with lower CO and higher TPR, compared to those with higher fitness. Considering fitness when interpreting SBP and cardiac imaging results from exercise stress testing may be relevant in identifying CVD risk and optimal patient management.