Coronary Microvascular Function Assessment using the Coronary Angiography-Derived Index of Microcirculatory Resistance in Patients with ST-segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention.

BACKGROUND

Studies reporting the status of coronary microvascular function in the infarct-related artery (IRA) after primary percutaneous coronary intervention (PCI) remain limited. This study utilized the coronary angiography-derived index of microcirculatory resistance (caIMR) to assess coronary microvascular function in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary PCI.

METHODS

We used the FlashAngio system to measure the caIMR after primary PCI in 157 patients with STEMI. The primary endpoint was the occurrence of a major adverse cardiovascular event (MACE), defined as a composite endpoint encompassing cardiac mortality, target vessel revascularization, and rehospitalization due to congestive heart failure (CHF), myocardial infarction (MI), or angina.

RESULTS

Approximately 30% of patients diagnosed with STEMI and who experienced successful primary PCI during the study period had a caIMR in the IRA of 40. The caIMR in the IRA was significantly higher than in the reference vessel (32.9 15.8 vs. 27.4 11.1, 0.001). The caIMR in the reference vessel of the caIMR 40 group was greater than in the caIMR 40 group (30.9 11.3 vs. 25.9 10.7, = 0.009). Moreover, the caIMR 40 group had higher incidence rates of MACEs at 3 months (25.5% vs. 8.3%, = 0.009) and 1 year (29.8% vs. 13.9%, = 0.04), than in the caIMR 40 group, which were mainly driven by a higher rate of rehospitalization due to CHF, MI, or angina. A caIMR in the IRA of 40 was an independent predictor of a MACE at 3 months (hazard ratio (HR): 3.459, 95% confidence interval (CI): 1.363-8.779, = 0.009) and 1 year (HR: 2.384, 95% CI: 1.100-5.166, = 0.03) in patients with STEMI after primary PCI.

CONCLUSIONS

Patients with STEMI after primary PCI often have coronary microvascular dysfunction, which is indicated by an increased caIMR in the IRA. An elevated caIMR of 40 in the IRA was associated with an increased risk of adverse outcomes in STEMI patients undergoing primary PCI.