Infarct size has been considered an established marker of left ventricular (LV) remodeling. We assessed the predictive value of myocardial/microvascular injury assessed by delayed enhanced magnetic resonance imaging (MRI) on LV remodeling and LV ejection fraction after primary coronary intervention (PCI) compared with peak
troponin levels, an established index of
myocardial infarct size. We performed MRI in 76 patients with first acute
myocardial infarction 6 +/- 2 days after successful PCI.
Necrosis was judged as transmural when delayed enhancement was extended to >or=75% of LV segment thickness. Severe microvascular obstruction was identified as areas of late hypoenhancement surrounded by delayed enhancement.
Infarct size was expressed as an index by dividing the total percentage of delayed enhancement involvement by the number of LV segments. LV end-diastolic volume index and function were quantified by 2-dimensional echocardiography at 6 +/- 1 months after acute
myocardial infarction. Remodeling was evaluated as a change in LV end-diastolic volume index at follow-up compared with baseline. At univariate analyses, transmural
necrosis, severe microvascular obstruction,
infarct size, and
troponin level were correlated directly with remodeling and inversely with LV function at follow-up (p <0.001). At multiple regression, only transmural
necrosis and
troponin level remained independent predictors of LV remodeling and function. With respect to
troponin, transmural
necrosis improved the predictive power of LV remodeling (R2 for change = 0.19) and function (R2 for change = 0.16). In conclusion, in patients with acute
myocardial infarction undergoing PCI, the amount of transmural
necrosis as assessed by MRI is a major determinant of LV remodeling and function, with significant additional predictive value to
infarct size and severe microvascular obstruction.