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Treadmill-based submaximal VO2 estimation in patients with coronary artery disease: can a model derived from healthy
Levent Karataş1, Esra Sena Orbak Yenidünya1, Nesrin Demirsoy1
1Department of Physical Medicine and Rehabilitation, Faculty of Medicine, Gazi University, Ankara, Turkiye.
Background/Aim:
Existing treadmill-based VO2 prediction models may not accurately estimate submaximal VO2 in patients with coronary artery disease (CAD), as they are often derived from healthy populations. This study aimed to develop and validate a submaximal VO2 prediction model derived from healthy individuals and tested for generalizability in CAD patients by incorporating clinically relevant parameters.
Materials And Methods:
A retrospective analysis was conducted with 101 participants (54 healthy, 47 CAD patients) undergoing cardiopulmonary exercise testing using the modified Bruce protocol. To better represent the submaximal VO2 reached during exercise, the average VO2 in the last minute of each stage was used. The model was developed using data from healthy individuals and subsequently validated in the CAD cohort. A linear mixed-effects model was employed to predict VO2 based on speed, grade, and other confounders, including peak VO2, body weight, and body mass index (BMI). The model's performance was evaluated and compared with previously published equations using Bland-Altman plots, mean absolute error (MAE), root mean square error (RMSE), and Lin's concordance correlation coefficient (CCC).
Results:
The final model, including speed, grade, and peak VO2, achieved an R2 of 0.83 (95% CI: 0.79, 0.86; f2 = 4.88). For CAD patients, the predicted-actual VO2 difference was -0.05 ± 1.8 mL/kg/min, with MAE and RMSE values of 1.4 and 1.8 mL/kg/min, respectively. The model outperformed reference equations, achieving the highest accuracy (CCC = 0.923) and minimal bias. Incorporating peak VO2 effectively accounted for exercise response differences between healthy individuals and CAD patients.
Conclusion:
A submaximal VO2 estimation model derived from healthy individuals and validated in CAD patients demonstrated high accuracy. Incorporating peak VO2 effectively bridged physiological differences, supporting individualized exercise prescriptions in cardiac rehabilitation. However, larger prospective cohorts are warranted to confirm external validity.
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