Figure 2. Study flowchart.

The study comprised a derivation cohort and a validation cohort. The derivation cohort was used to determine the optimal cutoff value of AMR for diagnosing CMD. This value was then validated in the validation cohort. AMR: angiographic microcirculatory resistance; CMD: coronary microvascular dysfunction; CMR: cardiac magnetic resonance; IRA: infarct-related artery; PPCI: primary percutaneous coronary intervention; QFR: quantitative flow ratio; STEMI: ST-segment elevation myocardial infarction