Left ventricular ejection fraction (EF) late after myocardial infarction determines whether patients will benefit from cardioverter/defibrillator (CV/D) implantation. At present, patients with acute ST elevation myocardial infarction (STEMI) are evaluated several months later to determine EF and CV/D indication following initial recovery. We determined whether contrast-enhanced MRI (CE-MRI) in the hyperacute phase of STEMI could predict late myocardial recovery. 50 patients with STEMI underwent CE-CMR within 12 hours of primary angioplasty (median 4h). All had follow-up CE-CMR >6 months later. Global and segmental left ventricular function, morphology, perfusion and necrosis were determined and assessed by validated techniques (QMass, Medis, the Netherlands). In the hyperacute phase of STEMI, a greater cardiac output (4.2 vs 3.4 L/min, p=0.01) was measured due to significantly greater heart rate (72 vs 57 bpm, p<0.01) despite similar stroke volumes (59 vs 60mL, p=NS) compared to >6 months later. On average, LVEF did not significantly change from hyperacute STEMI to recovered phase (51 vs 54%, p=NS) but systolic wall thickening increased on average from 41 to 50% (p=0.01) due to compensatory increased systolic thickening of non-infarct related segments. LV mass decreased from 120 to 105 g (p=0.01) due to a decrease in mean wall thickness driven by infarct segment wall thinning (9.2 vs 8.4mm, p<0.01). Microvascular function improved significantly (time to 50% enhancement on first-pass CE-MRI: 24.3 vs 21.7ms, p=0.03). Contrary to prior reports of “scar shrinkage” comparing necrosis in the first week after STEMI and 6 months later, necrosis relative to total myocardial volume did not differ between the hyperacute phase and >6 months (20 vs 18%, p=0.46). Furthermore, the transmural extent of necrosis, a potent predictor of functional recovery, did not significantly change from the hyperacute to the recovered phase of STEMI (mean 17 vs 14%, p=0.38). CE-MRI in the hyperacute phase of STEMI is a powerful predictor of long-term myocardial function and necrosis which could prove useful for very early risk stratification and future targeting of appropriate therapies.
AN EARLY PREDICTION MODEL FOR FUNCTIONAL MYOCARDIAL RECOVERY IN ST ELEVATION MYOCARDIAL INFARCTION