Affiliation:
1. Department of Cardiology Nepean Hospital Sydney New South Wales Australia
2. Sydney Medical School Nepean, Faculty of Medicine and Health, Charles Perkins Centre Nepean The University of Sydney New South Wales Australia
3. Faculty of Health and Medicine The University of Newcastle Newcastle New South Wales Australia
4. BHF Cardiovascular Research Centre, University of Glasgow College of Medical Veterinary and Life Sciences Glasgow UK
Abstract
AbstractBackgroundMicrovascular obstruction (MVO) is an independent predictor of adverse cardiac events after ST‐elevation myocardial infarction (STEMI). The Index of Microcirculatory Resistance (IMR) may be a useful marker of MVO, which could simplify the care pathway without the need for Cardiac Magnetic Resonance (CMR). We assessed whether the IMR can predict MVO in STEMI patients.Methods and ResultsWe conducted a systematic review and meta‐analysis, including articles where invasive IMR was performed post primary percutaneous coronary intervention (PCI) in addition to MVO assessment with cardiac MRI. We searched PubMed, Scopus, Embase, and Cochrane databases from inception until January 2023. Baseline characteristics, coronary physiology and cardiac MRI data were extracted by two independent reviewers. The random‐effects model was used to pool the data. Among 15 articles identified, nine articles (n = 728, mean age 61, 81% male) contained IMR data stratified by MVO. Patients with MVO had a mean IMR of 41.2 [95% CI 32.4−50.4], compared to 25.3 [18.3−32.2] for those without. The difference in IMR between those with and without MVO was 15.1 [9.7−20.6]. Meta‐regression analyses demonstrated a linear relationship between IMR and TIMI grade (β = 0.69 [0.13−1.26]), as well as infarct size (β = 1.18 [0.24−2.11]) or ejection fraction at 6 months (β = −0.18 [−0.35 to −0.01]).ConclusionIn STEMI, patients with MVO had 15‐unit higher IMR than those without. IMR also predicts key prognostic endpoints such as infarct size, MVO, and long‐term systolic function.