[Early study of myocardial perfusion with MRI in revascularized infarcts]

The aim of this work is to study the regional myocardial perfusion by MRI early after revascularised myocardial infarction and to compare it with regional function. This prospective work has included 15 patients with acute first myocardial infarction that was precociously revascularised. A myocardial MRI was performed between D2 and D10 after myocardial infarction. The regional myocardial thickening was evaluated from cine-MRI sequences. For the study of myocardial perfusion, the first pass of the contrast agent was analysed from curves of the signal evolution versus time. The signal enhancement on late images acquired 10 minutes after the perfusion of the contrast agent was also evaluated. Among 384 studied myocardial segments, those with a normal gadolinium first pass curve had a relative thickening of 46 +/- 38%. The segments with a severely reduced first pass kinetic have a markedly reduced relative thickening (14 +/- 20%) in relation with myocardial hypoperfusion. The myocardial enhancement is frequently seen in the infarct territory and appears related to a reduced regional contractility. The myocardium is enhanced on late images in 12% of the normally perfused segments. These segments have a mildly reduced wall thickening (3.36 +/- 2.84 mm vs 4.42 +/- 2.83 mm). The segmental contractility in a reperfused myocardial infarction appears to depend both on the myocardial perfusion which reflects the microvascularisation and on the myocardial enhancement which is linked to myocardial structural alterations. MRI appears to be an adequate method to evaluate these abnormalities and allows an easy assessment of the no-reflow phenomenon, if present.