Characterization of microvascular dysfunction after acute myocardial infarction by cardiovascular magnetic resonance first-pass perfusion and late gadolinium enhancement imaging.

Purpose: While both first-pass perfusion and late gadolinium enhancement by cardiovascular magnetic resonance (CMR) can assess coronary microvascular status in acute myocardial infarction (AMI), there are only limited data on their respective diagnostic utility. We aim to evaluate: the utility of first-pass perfusion and late gadolinium enhancement imaging in the detection and quantification of microvascular dysfunction after reperfused acute myocardial infarction, using TIMI frame count (TIMI FC) as the reference standard of microvascular assessment; and their relationship with infarct size and ventricular function.

Methods: First-pass perfusion and late gadolinium enhancement imaging were performed in 25 consecutive AMI patients (84% men, age 58 +/- 10) within 72 h of successful reperfusion. We assessed the myocardial extent of microvascular dysfunction using the size of the perfusion defect on first-pass perfusion (PD%) and the hypoenhanced core region within late gadolinium enhancement (MDEcore%). PD%, MDEcore%, and TIMI FC were analyzed independently of each other and with blinding to clinical data. We adjusted PD% and MDEcore% to the myocardial mass subtended by the infarct-related artery according to the 16-segment model.

Results: Median infarct size involved 13.9% (interquartile range: 8.5 to 22.2%) of the left ventricle and median left ventricular ejection fraction was 52% (interquartile range: 43 to 61%). PD% demonstrated evidence of microvascular dysfunction more frequently (84% vs. 36% of patients, p < 0.002) and involved a larger myocardial extent (23.5 +/- 17.5% vs. 3.5 +/- 7.7%, p < 0.001) compared to MDEcore%. PD% had strong correlations with TIMI FC (Spearman rho = 0.62, p < 0.001) and infarct size (rho = 0.64, p < 0.001), and a moderate correlation with LVEF (rho = -0.39, p = 0.055). MDEcore% also correlated with TIMI FC (rho = 0.54, p = 0.005) and infarct size (rho = 0.52, p < 0.01) but not with LVEF (p = NS).

Conclusions: PD% appeared to provide a stronger noninvasive assessment of the microvascular function than MDEcore% and correlated well with prognostic markers such as left ventricular ejection fraction and infarct size. Future studies should consider quantitative analyses of both first-pass perfusion and late gadolinium enhancement imaging in the evaluation of novel therapies targeted to the microvasculature of the infarct-related artery.