[Assessment of myocardial function and perfusion by MRI two days and four months after acute myocardial infarction revascularised by primary angioplasty].

The extent of gadolinium enhancement assessed by cardiac MRI is an accepted marker of myocardial necrosis. The correlation between late enhancement and other parameters of infarct size after myocardial infarction have previously been described. However, the prognostic value of the extent of late enhancement in terms of myocardial recovery remains controversial especially in revascularised infarcts analysed by early MRI. In order to clarify this question the authors compared the results of MRI at two days and four months after myocardial infarction benefiting from early revascularisation. Between July 2002 and November 2004, the authors included patients with myocardial infarction treated by primary angioplasty and examined by MRI (Siemens Symphony 1.5 T) at two days and three to five months after myocardial infarction. The left ventricular ejection fraction, volume, mass and wall thickness were measured. Perfusion at first passage (PP) and late enhancement were analysed after injection of 20 cc of gadolinium. An eight segment short axis model was used for PP and analysis of late enhancement. Each segment was assessed for transmural or subendocardial hypoperfusion for PP assessment and the wall thickness with late enhancement (1-25%, 26-50%, 51-75%, and 76-100%) was measured to calculate the percentage of myocardial mass showing late enhancement. Thirty-nine patients (thirty three men) were included. The average age was 59 +/- 10 years. TIMI III flow was obtained in all but one (TIMI II) patient. Cardiac MRI was performed 2.1 +/- 1.5 days and 4.6 +/- 1.7 months after myocardial infarction. The ejection fraction increased from 48.7 +/- 12.6% to 54.2 +/- 11.1%, p<0.05, and was related to infarct size (p<0.01). Forty-eight per cent of dysfunctional segments at the initial MRI improved their contractility and the extent of transmural late enhancement was inversely correlated with wall thickening at initial (p<0.01) and four month MRI (p<0.01). The PP improved significantly (regression from 9.5 +/- 8.2% to 2.8 +/- 4.1% of segments with abnormal myocardial perfusion, p<0.01). The late enhancement with respect to total myocardial mass decreased from 20.0 +/- 10.7% to 13.0 +/- 8.1%, p<0.01). Despite restoring TIMI III flow, early myocardial reperfusion is incomplete and improves in the medium term. The authors also observed a reduction in late enhancement at four months, indicating that the results immediately after myocardial infarction may overestimate the infarct size and that this sign does not represent necrotic tissue alone but also viable myocardium with a potential for recovery.