High Index of Microcirculatory Resistance Level After Successful Primary Percutaneous Coronary Intervention Can Be Improved by Intracoronary Administration of Nicorandil

Background: Although microvascular dysfunction following percutaneous coronary intervention (PCI) can be evaluated with the index of microcirculatory resistance (IMR), no method of treatment has been established. We hypothesized that intracoronary administration of nicorandil can improve IMR after successful primary PCI in patients with ST-segment elevation myocardial infarction (STEMI). Methods and Results: In 40 patients with first STEMI after successful primary PCI, IMR was measured using PressureWireTM Certus (St. Jude Medical, MN, USA). In 20 of the patients (Group N), IMR was measured at baseline and after intracoronary nicorandil (2 mg/10 ml). In the other 20 patients (Control), IMR was measured at baseline, after intracoronary saline (10 ml) and after intracoronary nicorandil (2 mg/10 ml). In Group N, IMR significantly decreased after intracoronary nicorandil (median IMR, 27.7-18.7 U, P