Contrast-enhanced magnetic resonance imaging reveals early decrease of transmural extent of reperfused acute myocardial infarction.

In patients with myocardial infarction infarct size and transmural extent are of high prognostic value for clinical outcome and recovery of contractile function of the affected myocardium either spontaneously or after revascularisation. Delayed contrast-enhancement magnetic resonance imaging (DCE-MRI) is a non-invasive imaging technique of high accuracy for determination of myocardial infarct size and transmural extent. As decisions whether revascularisation procedures are promising in patients with coronary artery disease are increasingly based on the transmural infarct extent assessed by DCE-MRI we sought to examine whether the timing of MRI after acute myocardial infarction would influence the transmural extent. We performed DCE-imaging on a clinical 1.5 T scanner in patients at day-1 and day-7 after reperfused STEMI. We assessed the total number of segments displaying DCE as well as differentiated by the transmural infarct extent. The total number of affected segments as well as the number of segments with only subendocardial DCE did not change between day-1 and day-7. In contrast, we observed a significant decrease of the number of segments with DCE of > or =75% transmurality and a significant increase of segments with DCE grade III (51%-75% transmurality). We conclude that the transmural infarct extent is not stable over the first days after STEMI which should be taken into account when assessing viability in clinical and research settings.

Very early cardiac magnetic resonance imaging for quantification of myocardial tissue perfusion in patients receiving tirofiban before percutaneous coronary intervention for ST-elevation myocardial infarction.

BACKGROUND: Assessment of myocardial blood flow is important for identification and monitoring of microvascular effects of glycoprotein IIb/IIIa inhibitors. Magnetic resonance imaging is a novel noninvasive method providing complementary information on myocardial blood flow and cardiac function. METHODS AND RESULTS: Patients (n = 53) admitted within 12 (mean, 5.8) hours after onset of symptoms were randomized to tirofiban or standard therapy before primary percutaneous coronary intervention (PCI) with stenting. Myocardial blood flow was graded by measurement of corrected Thrombolysis in Myocardial Infarction frame counts and by semiquantitative analysis of signal intensity curves from first-pass contrast-enhanced magnetic resonance perfusion. Pretreatment with tirofiban proved safe and resulted in a significantly lower corrected Thrombolysis in Myocardial Infarction frame counts (21 vs 34, P = .008) indicating improved myocardial blood flow. Magnetic resonance imaging revealed higher normalized peak signal intensities (2.19 vs 1.63, P = .046) and a trend to steeper upslopes (0.79 vs 0.48, P = .1). Cardiac left ventricular wall motion analysis resulted in a significantly lower number of myocardial segments with abnormal wall thickening (6.4 vs 8.5, P = .025). CONCLUSIONS: Pretreatment with tirofiban appears safe and improves myocardial flow after primary PCI with stenting. Magnetic resonance imaging proved useful as a complementary method for noninvasive assessment of myocardial blood flow and cardiac function in patients with ST-segment elevation myocardial infarction undergoing primary PCI.