Acute microvascular impairment post-reperfused STEMI is reversible and has additional clinical predictive value: a CMR OxAMI study

Objectives This study sought to investigate the clinical utility and the predictive relevance of absolute rest myocardial blood flow (MBF) by cardiac magnetic resonance (CMR) in acute myocardial infarction. Background Microvascular obstruction (MVO) remains one of the worst prognostic factors in patients with reperfused ST-segment elevation myocardial infarction (STEMI). Clinical trials have focused on cardioprotective strategies to maintain microvascular functionality, but there is a need for a noninvasive test to determine their efficacy. Methods A total of 64 STEMI patients post–primary percutaneous coronary intervention underwent 3-T CMR scans acutely and at 6 months (6M). The protocol included cine function, T2-weighted edema imaging, pre-contrast T1 mapping, rest first-pass perfusion, and late gadolinium enhancement imaging. Segmental MBF, corrected for rate pressure product (MBFcor), was quantified in remote, edematous, and infarcted myocardium. Results Acute MBFcor was significantly reduced in infarcted myocardium compared with remote MBF (MBFinfarct 0.76 ± 0.20 ml/min/g vs. MBFremote 1.02 ± 0.21 ml/min/g, p < 0.001), but it significantly increased at 6M (MBFinfarct 0.76 ± 0.20 ml/min/g acute vs. 0.85 ± 0.22 ml/min/g at 6M, p < 0.001). On a segmental basis, acute MBFcor had incremental prognostic value for infarct size at 6M (odds of no LGE at 6M increased by 1.4:1 [p < 0.001] for each 0.1 ml/min/g increase of acute MBFcor) and functional recovery (odds of wall thickening >45% at 6M increased by 1.38:1 [p < 0.001] for each 0.1 ml/min/g increase of acute MBFcor). In subjects with coronary flow reserve >2 or index of myocardial resistance <40, acute MBF was associated with long-term functional recovery and was an independent predictor of infarct size reduction. Conclusions Acute MBF by CMR could represent a novel quantitative imaging biomarker of microvascular reversibility, and it could be used to identify patients who may benefit from more intensive or novel therapies