Microcirculatory significance of periprocedural myocardial necrosis after percutaneous coronary intervention assessed by the index of microcirculatory resistance.

This study sought to investigate the relationship between the index of microcirculatory resistance (IMR) and periprocedural myocardial necrosis in patients with unstable angina pectoris (UAP). Fifty-seven UAP patients undergoing elective percutaneous coronary intervention (PCI) of a single lesion were recruited. A pressure-temperature sensor wire was used to measure IMR immediately after PCI. Total creatine kinase-MB (CK-MB) and troponin I (TNI) were measured every 8 h after PCI until they began to decline. Of the 57 patients studied, 22 had periprocedural myocardial infarction (MI) according to TNI. Post-PCI IMR >31 U had 86% sensitivity and 91% specificity for predicting periprocedural MI. There are a strong positive correlation between IMR and peak TNI (r = 0.805, p = 0.001), and a moderate positive correlation between IMR and peak CK-MB (r = 0.608, p = 0.003). Periprocedural myocardial injury, even in small area, during reperfusion is associated with impaired microcirculatory integrity as evaluated by IMR. Post-PCI IMR is independent predictive of developing periprocedural MI in patients with UAP, and, therefore, potentially enables a triage of higher risk patients to more intensive therapy.