Influence of Fitness on Exercise Blood Pressure and Cardiac Structure: Data from the Exercise Stress Test Collaboration (EXERTION).

PURPOSE: An abnormally high exercise systolic blood pressure (SBP) is associated with adverse left ventricular (LV) remodelling, a hallmark of hypertensive-heart disease. Fitness may modify this relationship through its effects on BP and cardiac structure, influencing the interpretation of exercise test results. This study explored the influence of fitness on the exercise SBP-cardiac structure relationship in individuals undergoing exercise stress echocardiography. METHODS: Cardiovascular structure and function (LV mass indexed to body surface area (LVMIBSA), relative wall thickness (RWT), cardiac output (CO) and total peripheral resistance (TPR)) were assessed by echocardiography in 5,087 individuals (aged 59.7±12.7 years, 53.1% male). BP was measured at peak exercise workload. Fitness was estimated by maximal oxygen consumption (VO2max) and categorised into three groups (low, moderate and high) based on age- and sex-predicted VO2max values. Regression analysis examined interactions of fitness on the exercise SBP-LV structure relationship, adjusting for age, sex, pre-exercise SBP, and history of cardiovascular disease. RESULTS: Peak SBP was positively associated with LVM, LVMIBSA and RWT (all p<0.005). Fitness modified these relationships; SBP was associated with LVM and LVMIBSA in moderate and high fitness (all p<0.05), but not in the low fitness group (p>0.40). RWT increased with SBP across all groups (all p<0.05), with highest values observed in the low fitness group (p<0.001). CO was lower and TPR higher in the low fitness (8.7±3.0L/min and 12.6±4.6mmHg·min/L) compared to high fitness (10.1±3.2L/min and 10.2±3.4mmHg·min/L) (all p<0.001). CONCLUSIONS: Fitness modifies the relationship between exercise SBP and cardiac structure, with low fitness exhibiting more adverse cardiovascular adaptations despite similar peak exercise SBP. Incorporating fitness into interpretation of peak exercise SBP is relevant for clinical decision-making.