Submaximal measures of fitness and left ventricular size: associations and utility in differentiating physiological and pathological enlargement

Abstract Background Peak oxygen uptake (VO2peak) has been shown to better differentiate between physiological and pathological left ventricular (LV) remodelling compared to indexing to body surface area (BSA). This study aimed to investigate the relationship between LV end-diastolic volume (LVEDV) and submaximal measures of cardiorespiratory fitness (oxygen uptake at the ventilatory threshold; VO2VT, and at the cardiorespiratory optimal point; VO2COP), and to evaluate whether these measures could serve as alternatives for indexing to VO2peak. Methods Transthoracic echocardiography and cardiopulmonary exercise testing (CPET) where performed in 1067 health-survey participants free from cardiovascular disease, 39 healthy recreational athletes, and 53 patients with heart failure. Pearson’s correlation and linear regression were performed to evaluate associations between LVEDV and VO2VT, VO2COP, VO2peak, and BSA. Indexing methods were compared for their ability to classify LV size. Results The VO₂VT (R2 = 0.44) and VO₂COP (R2 = 0.41) showed stronger correlations with LVEDV and explained a greater proportion of its variance than BSA (R2 = 32%, both p <0.01), although weaker than VO2peak (R2 = 0.52, p <0.01). Indexing LVEDV to VO2VT and VO2COP significantly increased the proportion of patients with heart failure classified with enlarged ventricles compared to BSA, and reduced misclassification among athletes. The submaximal measures performed similarly to VO2peak in this classification. Conclusion Submaximal measures of fitness (VO2VT and VO2COP) showed a similar ability to distinguish between pathological and physiological LV enlargement as maximal measures (VO2peak), and better than BSA. Submaximal measures may offer practical fallback alternatives when maximal exercise testing is not feasible.