International Journal of Cardiology Congenital Heart Disease (Dec 2024)
Oxygen uptake efficiency slope at anaerobic threshold can predict peak VO2 in adult congenital heart disease
Abstract
Introduction: Assessment of exercise capacity by cardiopulmonary exercise testing (CPET) in adults with congenital heart disease (CHD) is important for prognostication and preoperative assessment. Peak oxygen uptake (PVO2) is used commonly, but can be challenging due to the difficulties of undertaking maximal CPET testing in this population. We explored whether oxygen uptake efficiency slope (OUES) at ventilatory anaerobic threshold (VAT), the point during CPET at which OUES becomes strongly correlated with PVO2, and is more reliably available from submaximal CPET, can predict PVO2 in adults with CHD. Methods: We assessed consecutive individuals who completed maximal CPET at our cardiorespiratory centre, as part of routine service review, between March 2019 and August 2021, recording data such as PVO2, VAT and OUES at various proportions of a maximal test (75 %, 90 %, 100 %, and VAT). We employed linear regression modelling to analyse the association between PVO2 and OUES at VAT, and subsequently create an equation to predict PVO2 from OUES at VAT. Parametric data are presented using Pearson's correlation coefficient and non-parametric data using Spearman's rho. Results: We analysed 391 individuals (177 female, age 32 ± 11 years). Mean ± SD PVO2 was 23.3 ± 6.86 ml/min/kg or 1724 ± 540 ml/min, peak VE 86.7 ± 25.4 l/min. The point of VAT as a percentage of PVO2 achieved was 66.5 ± 9.4 %, and VAT as a percentage of predicted PVO2 46.9 ± 11.4 %. PVO2 was correlated with OUES at 100 % (R = 0.91, P < .001), 90 % (R = 0.91, P < .001), 75 % (R = 0.89, P < .001) of maximum, and VAT (R = 0.83, P < .001). PVO2 (ml/min) could be predicted by: (OUES at VAT)∗685.245 + (BMI [kg/m2])∗5.045 + (FEV1 [l])∗223.620 – 153.205. Conclusions: OUES at VAT can be used to calculate PVO2. To our knowledge, this is the first equation using OUES at VAT to predict PVO2 in adults with CHD. In a population who may find maximal CPET difficult, this may be a useful submaximal measurement of cardiovascular fitness, and to calculate PVO2, which is commonly used in guideline-based decision making in CHD.
