LAUSR

Importance Percutaneous coronary intervention (PCI) of nonculprit vessels among patients with ST-segment elevation myocardial infarction (STEMI) is associated with improved clinical outcome compared with culprit vessel-only PCI. Fractional flow reserve (FFR) and coronary flow reserve are hyperemic indices used to guide revascularization. Recently, instantaneous wave-free ratio was introduced as a nonhyperemic alternative to FFR. Whether these indices can be used in the acute setting of STEMI continues to be investigated. Objective To assess the value of hemodynamic indices in nonculprit vessels of patients with STEMI from the index event to 1-month follow-up. Design, Setting, and Participants This substudy of the Reducing Micro Vascular Dysfunction in Revascularized STEMI Patients by Off-target Properties of Ticagrelor (REDUCE-MVI) randomized clinical trial enrolled 98 patients with STEMI who had an angiographic intermediate stenosis in at least 1 nonculprit vessel. Patient enrollment was between May 1, 2015, and September 19, 2017. After successful primary PCI, nonculprit intracoronary hemodynamic measurements were performed and repeated at 1-month follow-up. Cardiac magnetic resonance imaging was performed from 2 to 7 days and 1 month after primary PCI. Main Outcomes and Measures The value of nonculprit instantaneous wave-free ratio, FFR, coronary flow reserve, hyperemic index of microcirculatory resistance, and resting microcirculatory resistance from the index event to 1-month follow-up. Results Of 73 patients with STEMI included in the final analysis, 59 (80.8%) were male, with a mean (SD) age of 60.8 (9.9) years. Instantaneous wave-free ratio (SD) did not change significantly (0.93 [0.07] vs 0.94 [0.06]; P = .12) and there was no change in resting distal pressure/aortic pressure (mean [SD], 0.94 [0.06] vs 0.95 [0.06]; P = .25) from the acute moment to 1-month follow-up. The FFR decreased (mean [SD], 0.88 [0.07] vs 0.86 [0.09]; P = .001) whereas coronary flow reserve increased (mean [SD], 2.9 [1.4] vs 4.1 [2.2]; P < .001). Hyperemic index of microcirculatory resistance decreased and resting microcirculatory resistance increased from the acute moment to follow-up. The decrease in distal pressure from rest to hyperemia was smaller at the acute moment vs follow-up (mean [SD], 10.6 [11.2] mm Hg vs 14.1 [14.2] mm Hg; P = .05). This blunted acute hyperemic response correlated with final infarct size (ρ, -0.29; P = .02). The resistive reserve ratio was lower at the acute moment vs follow-up (mean [SD], 3.4 [1.7] vs 5.0 [2.7]; P < .001). Conclusions and Relevance In the acute setting of STEMI, nonculprit coronary flow reserve was reduced and FFR was augmented, whereas instantaneous wave-free ratio was not altered. These results may be explained by an increased hyperemic microvascular resistance and a blunted adenosine responsiveness at the acute moment that was associated with infarct size.