Abstract
Background: In STEMI, microvascular dysfunction often persists after reperfusion and increases complications. Assessment using IMR/angio-IMR is considered an effective method for evaluating coronary microvascular dysfunction. In Vietnam, there have been few studies assessing microvascular function through this index in patients with ST-elevation myocardial infarction.
Objective:To evaluate coronary microvascular function using the Index of Microcirculatory Resistance (IMR) in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI).
Methods: A prospective, descriptive study was conducted on 51 STEMI patients who underwent primary PCI. IMR, along with clinical, paraclinical, interventional characteristics, and 30-day post-procedural cardiovascular events, were analyzed.
Results: The mean IMR was 32.75 ± 12.12; 70.59% of patients had IMR ≤ 40, while 29.41% had IMR > 40. The IMR > 40 group showed a higher proportion of NYHA class III–IV (26.7% vs. 5.6%; p = 0.045), a lower left ventricular ejection fraction (44.0 ± 9.6% vs. 50.1 ± 9.0%; p = 0.035), and a lower rate of post-procedural TIMI 3 flow (46.7% vs. 94.4%; p < 0.0001). The 30-day post-procedural adverse event rate was 11.76%, including 13.3% in the IMR > 40 group (1 cardiac death and 1 case of angina) and 11.11% in the IMR ≤ 40 group (3 cases of target vessel revascularization and 1 case of angina). The difference in event rates between the two IMR groups was not statistically significant (p > 0.05).
Conclusion: IMR reflects microvascular dysfunction in STEMI patients, with the IMR >40 group showing poorer post-intervention coronary reperfusion. However, it has not yet demonstrated significance in predicting post-procedural events.