Intracoronary nicorandil improves coronary microcirculatory function after primary PCI in first-episode STEMI: an angiography-derived evaluation using AMR and QFR

Background: Microvascular dysfunction remains a major driver of adverse outcomes after ST-segment elevation myocardial infarction (STEMI) despite successful restoration of epicardial patency by primary percutaneous coronary intervention (PCI). Nicorandil has nitrate-like vasodilatory properties and ATP-dependent potassium channel (KATP)-opening properties, effects that may improve reperfusion physiology. However, its effects on wire-free, angiography-derived measures of microvascular function are not well defined. We evaluated whether intracoronary nicorandil administered during primary PCI improves angiography-derived microvascular function assessed by angiographic microcirculatory resistance (AMR) and quantitative flow ratio (QFR). Methods: = 31). The prespecified primary endpoint was final post-PCI AMR. QFR-derived indices, reperfusion measures [Thrombolysis in Myocardial Infarction (TIMI) flow grade, no-reflow, ST-segment resolution], hemodynamics, biomarkers, and clinical events were analyzed as secondary/exploratory outcomes, with multiplicity controlled using the Benjamini-Hochberg false discovery rate (FDR) where applicable. Results: = 0.027; q = 0.051). Peak creatine kinase-MB (CK-MB) and cardiac troponin I (cTnI) were numerically lower with nicorandil but not statistically different; left ventricular ejection fraction (LVEF) at 1 week was similar between groups. Rates of intra-procedural hypotension, in-hospital major adverse cardiovascular events (MACE), and MACE at 3-month follow-up did not differ. Conclusions: In this pilot randomized study, intracoronary nicorandil administered during primary PCI was associated with improved angiography-derived surrogate indices of microvascular resistance and epicardial physiology without an observed increase in peri-procedural hemodynamic instability or short-term adverse events. These findings should be interpreted as exploratory and warrant confirmation in larger multicenter studies with longer follow-up and outcome-linked validation.