Perfusion of Residual Viable Myocardium in Nontransmural Infarct Zone after Intervention: MR Quantitative Myocardial Blood Flow Measurement

Abstract

To assess regional myocardial perfusion in patients with chronic myocardial infarction (MI) in relationship to the extent of residual viable myocardium. The study was approved by the local ethics committee; written informed consent was obtained from each participant. Twenty-nine patients with first onset of MI who underwent successful primary percutaneous coronary intervention at least 6 months thereafter were studied. Delayed enhancement magnetic resonance (MR) imaging was performed to define the infarct zone and its viable myocardial ratio (VMR), quantified by the percentage of the nonscarred pixels relative to the total pixels in the infarct zone. First-pass contrast material-enhanced MR imaging was performed to estimate regional perfusion and myocardial perfusion reserve (MPR) in the infarct region. Paired comparisons in perfusion and MPR were tested with nonparametric Wilcoxon matched-pairs test. A difference with P < .05 was considered significant. Correlation was tested with Pearson analysis. The infarct region showed significant impairment of regional perfusion at rest (mean, 0.966 [mL x min(-1)]/g +/- 0.271 [standard deviation] vs 1.151 [mL x min(-1)]/g +/- 0.282; P = .024) and during stress (mean, 1.789 [mL x min(-1)]/g +/- 0.732 vs 2.753 [mL x min(-1)]/g +/- 0.806; P < .0001) and a reduced MPR (mean, 1.923 +/- 0.678 vs 2.486 +/- 0.836; P < .0001) as compared with remote myocardium. The estimated perfusion, with stress, of the residual viable myocardium was preserved (2.993 [mL x min(-1)]/g +/- 1.451 vs 2.753 [mL x min(-1)]/g +/- 0.806), and the difference was not significant. Furthermore, stress perfusion (R = 0.385; P = .039) and MPR (R = 0.434; P = .018) in the infarct zone were significantly correlated with VMR, suggesting that preservation of myocardial perfusion in the infarct region reflects the amount of viable myocardium. Reduced perfusion in the infarct zone is related to the extent of the viable myocardium.