Application of AMR in evaluating microvascular dysfunction after ST‐elevation myocardial infarction

Background A guidewire‐free angiography‐derived microcirculatory resistance (AMR) derived from Quantitative flow ratio (QFR) exhibits good diagnostic accuracy for assessing coronary microvascular dysfunction (CMD), but there are no relevant studies supporting the specific application of AMR in patients with ST‐elevation myocardial infarction (STEMI). The study aims to evaluate CMD in patients with STEMI using the AMR index. Methods This study included patients with STEMI who underwent percutaneous coronary intervention (PCI) from June 1, 2020 to September 28, 2021. All patients were divided into two groups: the CMD (n = 215) and non‐CMD (n = 291) groups. After matching, there were 382 patients in both groups.1‐year follow‐up major adverse cardiac events (MACEs) were evaluated. Results After matching, the primary endpoint was achieved in 41 patients (10.7%), with 27 and 14 patients in the CMD and non‐CMD groups, respectively (HR 1.954 [95% CI 1.025–3.726]; 14.1% versus 7.3%, p = .042). Subgroup analysis revealed that 18 patients (4.7%) were readmitted for heart failure, with 15 and 3 in the CMD and non‐CMD groups, respectively (HR 5.082 [95% CI 1.471–17.554]; 7.9% versus 1.6%, p = .010). Post‐PCI AMR ≥ 250 was significantly associated with a higher risk of the primary endpoint and was its independent predictor (HR 2.265 [95% CI 1.136–4.515], p = .020). Conclusion The retrospective use of AMR with a cutoff value of ≥250 after PCI in patients with STEMI can predict a significant difference in the 1‐year MACE rates when compared with a propensity score‐matched group with normal AMR. A guidewire‐free and adenosine‐free angiography‐derived microcirculatory resistance (AMR) derived from quantitative flow ratio with flow velocity calculation exhibits good diagnostic accuracy for assessing coronary microvascular dysfunction. In our study, post‐PCI AMR ≥ 250 mmHg × s/m was significantly associated with a higher risk of the primary endpoint and was its independent predictor.