Transmural extent of acute myocardial infarction predicts long-term improvement in contractile function

Background-Previous animal studies have demonstrated that the transmural ex tent of acute myocardial infarction defined by contrast-enhanced MRI (ceMRI ) relates to early restoration of flow and future improvements in contracti le function. We tested the hypothesis that ceMRI would have similar predict ive value in humans. Methods and Results-Twenty-four patients who presented with their first myo cardial infarction and were successfully revascularized underwent cine and ceMRI of their heart within 7 days (scan 1) of the peak MB band of creatine kinase. Cine MRI was repeated 8 to 12 weeks later (scan 2). The transmural extent of infarction on scan I and wall thickening on both scans were dete rmined using a 72-segment model. A total of 524 of 1571 segments (33%) were dysfunctional on scan 1. Improvement in segmental contractile function on scan 2 was inversely related to the transmural extent of infarction on scan 1 (P=0.001). Improvement in global contractile function, as assessed by ej ection fraction and mean wall thickening score, was not predicted by peak c reatine kinase-MB (P=0.66) or by total infarct size, as defined by MRI (P=0 .70). The best predictor of global improvement was the extent of dysfunctio nal myocardium that was not infarcted or had infarction comprising <25% of left ventricular wall thickness (P<0.005 for ejection fraction, P<0.001 for mean wall thickening score). Conclusion-In patients with acute myocardial infarction, the transmural ext ent of infarction defined by ceMRI predicts improvement in contractile func tion.