Angiography-derived index of microcirculatory resistance predicts long-term outcomes in late-presenting patients with ST-segment elevation myocardial infarction.

Background: The association between coronary microcirculatory function and long-term outcomes in late-presenting patients with ST-segment elevation myocardial infarction (STEMI) is unclear.

Methods: A total of 340 STEMI patients with late presentation (> 12 hours from the onset of symptoms) who underwent delayed percutaneous coronary intervention (PCI) were consecutively recruited from 2016 to 2021. The coronary microvasculature was assessed by angiography-derived index of microcirculatory resistance (caIMR) using commercial software. The primary endpoint was major adverse cardiovascular events (MACE) defined as a composite of all-cause death and myocardial infarction.

Results: The median symptom-to-angiography time was 149 hours (interquartile range [IQR], 101-192). The culprit vessels were completely occluded in 120 (35.3%) patients. During the follow-up with a median period of 51 months, MACE occurred in 27 patients (7.9%). After adjusting for risk factors, caIMR > 25 U after PCI was independently associated with an increased incidence of MACE (adjusted hazard ratio, 4.31; 95% confidence interval, 1.92-9.67; p < 0.001). The area under the curve (AUC) for caIMR in predicting MACE was 0.675 (p = 0.020).

Conclusions: Our study indicated that caIMR was an important prognostic predictor in late-presenting STEMI patients who underwent delayed PCI. Preservation of coronary microcirculatory function during PCI could provide long-term prognostic benefits.