Perfusion of residual viable myocardium in nontransmural infarct zone after intervention: MR quantitative myocardial blood flow measurement

Purpose: To assess regional myocardial perfusion in patients with chronic myocardial infarction (MI) in relationship to the extent of residual viable myocardium. Materials and Methods: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 non- scarred pixels relative to the total pixels in the infarct zone. First-pass contrast material-enhanced MR imaging was performed to estimate regional perfusion and myocar- dial perfusion reserve (MPR) in the infarct region. Paired comparisons in perfusion and MPR were tested with non-parametric Wilcoxon matched-pairs test. A difference with P < .05 was considered significant. Correlation was tested with Pearson analysis. Results: The infarct region showed significant impairment of regional perfusion at rest (mean, 0.966 [mL · min^-1]/g ± 0.271 [standard deviation] vs 1.151 [mL · min^-1]/g ± 0.282; P = .024) and during stress (mean, 1.789 [mL · min^-1]/g ± 0.732 vs 2.753 [mL · 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 · min^-1]/g ± 1.451 vs 2.753 [mL · 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 perfu- sion in the infarct region reflects the amount of viable myocardium. Conclusion: Reduced perfusion in the infarct zone is related to the extent of the viable myocardium.