Utility of the oxygen pulse in the diagnosis of obstructive coronary artery disease in physically fit patients.

Cardiopulmonary exercise testing (CPET) guidelines recommend analysis of the oxygen (O ₂ ) pulse for a late exercise plateau in evaluation for obstructive coronary artery disease (OCAD). However, whether this O ₂ pulse trajectory is within the range of normal has been debated, and the diagnostic performance of the O ₂ pulse for OCAD in physically fit individuals, in whom V ˙ O 2 may be more likely to plateau, has not been evaluated. Using prospectively collected data from a sports cardiology program, patients were identified who were free of other cardiac disease and underwent clinically-indicated CPET within 90 days of invasive or computed tomography coronary angiography. The diagnostic performance of quantitative O ₂ pulse metrics (late exercise slope, proportional change in slope during late exercise) and qualitative assessment for O ₂ pulse plateau to predict OCAD was assessed. Among 104 patients (age:56 ± 12 years, 30% female, peak V ˙ O 2 119 ± 34% predicted), the diagnostic performance for OCAD (n = 24,23%) was poor for both quantitative and qualitative metrics reflecting an O ₂ pulse plateau (late exercise slope: AUC = 0.55, sensitivity = 68%, specificity = 41%; proportional change in slope: AUC = 0.55, sensitivity = 91%, specificity = 18%; visual plateau/decline: AUC = 0.51, sensitivity = 33%, specificity = 67%). When O ₂ pulse parameters were added to the electrocardiogram, the change in AUC was minimal (-0.01 to +0.02, p ≥ 0.05). Those patients without OCAD with a plateau or decline in O ₂ pulse were fitter than those with linear augmentation (peak V ˙ O 2 133 ± 31% vs. 114 ± 36% predicted, p < 0.05) and had a longer exercise ramp time (9.5 ± 3.2 vs. 8.0 ± 2.5 min, p < 0.05). Overall, a plateau in O ₂ pulse was not a useful predictor of OCAD in a physically fit population, indicating that the O ₂ pulse should be integrated with other CPET parameters and may reflect a physiologic limitation of stroke volume and/or O ₂ extraction during intense exercise.
(© 2021 The Authors. Physiological Reports published by Wiley Periodicals LLC on behalf of The Physiological Society and the American Physiological Society.)