The association between O 2 -pulse slope ratio and functional severity of coronary stenosis: A combined cardiopulmonary exercise testing and quantitative flow ratio study.

Geng L; Department of Cardiology, East Hospital, Tongji University, Shanghai 200120, China.
Huang S; Zhang T; Wang L; Zhou J; Gao L; Wang Y; Li J; Guo W; Li Y; Zhang Q;

International journal of cardiology. Heart & vasculature [Int J Cardiol Heart Vasc] 2024 Apr 13; Vol. 52, pp. 101409.
Date of Electronic Publication: 2024 Apr 13 (Print Publication: 2024).

Background: The role of cardiopulmonary exercise testing (CPET) parameters in evaluating the functional severity of coronary disease remains unclear. The aim of this study was to quantify the O 2 -pulse morphology and investigate its relevance in predicting the functional severity of coronary stenosis, using Murray law-based quantitative flow ratio (μQFR) as the reference.
Methods: CPET and μQFR were analyzed in 138 patients with stable coronary artery disease (CAD). The O 2 -pulse morphology was quantified through calculating the O 2 -pulse slope ratio. The presence of O 2 -pulse plateau was defined according to the best cutoff value of O 2 -pulse slope ratio for predicting μQFR ≤ 0.8.
Results: The optimal cutoff value of O 2 -pulse slope ratio for predicting μQFR ≤ 0.8 was 0.4, with area under the curve (AUC) of 0.632 (95 % CI: 0.505-0.759, p =  0.032). The total discordance rate between O 2 -pulse slope ratio and μQFR was 27.5 %, with 13 patients (9.4 %) being classified as mismatch (O 2 -pulse slope ratio > 0.4 and μQFR ≤ 0.8) and 25 patients being classified as reverse-mismatch (O 2 -pulse slope ratio ≤ 0.4 and μQFR > 0.8). Angiography-derived microvascular resistance was independently associated with mismatch (OR 0.07; 95 % CI: 0.01-0.38, p =  0.002) and reverse-mismatch (OR 9.76; 95 % CI: 1.47-64.82, p =  0.018).
Conclusion: Our findings demonstrate the potential of the CPET-derived O 2 -pulse slope ratio for assessing myocardial ischemia in stable CAD patients