Correlation between coronary microvascular dysfunction and cardiorespiratory fitness in patients with ST-segment elevation myocardial infarction

We retrospectively investigated the relationship between cardiopulmonary exercise testing (CPET) parameters and coronary microvascular dysfunction (CMD) using a novel angiography-based index of microcirculatory resistance (AccuIMR) in patients with ST-elevation myocardial infarction (STEMI) who underwent primary percutaneous coronary intervention (PCI) with complete revascularization. In 418 patients, the culprit vessel AccuIMR was calculated after successful primary PCI. CPET was conducted 44.04 ± 19.28 days after primary PCI. Overall, 157 patients (37.6%) showed elevated AccuIMR (> 40 U) in the culprit vessels. The LVEF was significantly lower in the CMD group than in the Non-CMD group. The CMD group showed worse results in VO2peak, peak O2-pulse, and VE/VCO2 slope than the Non-CMD group. Spearman correlation analysis suggested that VO2peak (r = -0.354), peak O2-pulse (r = -0.385) and VE/VCO2 slope (r = 0.294) had significant linear correlations with AccuIMR (P < 0.001). Multivariable logistic regression analysis showed that AccuIMR was the independent predictor of reduced VO2peak and elevated VE/VCO2 slope. The proportions of positive and equivocal ECG results and early O2-pulse flattening in the CMD group were significantly higher than those in the Non-CMD group, and AccuIMR was the only independent predictor of these ischemia-relating indicators, suggesting that patients with CMD had significant noninvasively detectable myocardial ischemia.