El Farissi M, Zimmermann FM, De Maria GL, van Royen N, van Leeuwen MAH, Carrick D, Carberry J, Wijnbergen IF, Konijnenberg LSF, Hoole SP, Marin F, Fineschi M, Pijls NHJ, Oldroyd KG, Banning AP, Berry C, and Fearon WF
Background: Despite treatment with primary percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction (STEMI), the risk of heart failure and late death remains high. Microvascular dysfunction, as assessed by the index of microcirculatory resistance (IMR), after primary PCI for STEMI has been associated with worse outcomes. It is unclear whether IMR after primary PCI predicts cardiac death., Objectives: The aims of this analysis were: 1) to determine if IMR is an independent predictor of cardiac death; 2) to assess the optimal cutoff value of IMR after STEMI; and 3) to compare IMR with several cardiac magnetic resonance parameters, including infarct size., Methods: In a collaborative, pooled analysis of individual patient data from 6 cohorts that measured IMR directly after primary PCI, cardiac mortality up to 5 years was estimated using Kaplan-Meier analyses. The primary endpoint was cardiac death using the predefined IMR cutoff value of 40., Results: In total, 1,265 patients were included in this study with a median follow-up of 2.8 years (IQR: 1.2-5.0 years). Cardiac death at 5 years occurred in 2.2% and 4.9% of patients (HR: 2.81; 95% CI: 1.34-5.88; P = 0.006) in the IMR ≤40 and IMR >40 groups, respectively. The composite of cardiac death or hospitalization for heart failure occurred in 4.9% and 8.9% (HR: 1.98; 95% CI: 1.20-3.29; P = 0.008) in the IMR ≤40 and IMR >40 groups, respectively. IMR was an independent predictor of cardiac death, whereas coronary flow reserve was not. The optimal cutoff value of IMR for the prediction of cardiac death in this cohort was 70 (HR: 4.73; 95% CI: 2.27-9.83; P < 0.001). Infarct size was 17.6% ± 13.3% and 23.9% ± 14.6% of the left ventricular mass in the IMR ≤40 and IMR >40 groups, respectively (P < 0.001). Microvascular obstruction and intramyocardial hemorrhage occurred more frequently in the IMR >40 group than in the IMR ≤40 group., Conclusions: In this large, pooled analysis of individual patient data, IMR measured directly after primary PCI in STEMI was an independent predictor of cardiac death. IMR may be used as a tool to identify patients at the time of primary PCI who are at highest risk for late cardiac mortality and who might benefit most from additional cardioprotective therapies and monitoring., Competing Interests: Funding Support and Author Disclosures Dr van Royen has received research funding from Abbott, Philips, Medtronic, and Biotronik; has served as a consultant for RainMed, Castor, and Medtronic; and has received speaker fees from Abbott and Bayer. Dr van Leeuwen has received speaker/consulting service honoraria from Terumo, Daiichi Sankyo, and Abbott; and has received research grants from AstraZeneca, Top Sector Life Sciences and Health, Terumo, Top Medical BV, and Abbott. Dr Fineschi has received speaker honoraria and consulting fees from St. Jude Medical Italia (now Abbott). Dr Pijls has received institutional research grants from Abbott and Hexacath; is a consultant for Abbott and Opsens; holds minor equity interest in Philips, ASML, HeartFlow, and GE; is a member of the Scientific Advisory Board of HeartFlow; and has patents pending on diagnostic methods for quantifying aortic valve stenosis and microvascular physiology. Dr Berry has received institutional grants/contracts from Abbott, AstraZeneca, Boehringer Ingelheim, GlaxoSmithKline, HeartFlow, Novartis, and Siemens Healthcare; has received consulting fees from Abbott, AstraZeneca, Boehringer Ingelheim, GlaxoSmithKline, HeartFlow, Menarini, and Novartis; and has received honoraria from Abbott, AstraZeneca, Boehringer Ingelheim, GlaxoSmithKline, HeartFlow, Philips, and Valo Health. Dr Oldroyd has received honoraria from Abbott, Biosensors International, and Boston Scientific; has received an institutional research grant from Boston Scientific that supported the present manuscript; and is a full-time employee of Biosensors International since May 2020. Dr Fearon has received research support from Abbott, Boston Scientific, Edwards Lifesciences, and Medtronic; has consulting agreements with CathWorks and Siemens; and has equity options with HeartFlow., (Published by Elsevier Inc.)