Usefulness of MRI to Differentiate Between Temporary and Long-Term Coronary Artery Occlusion in a Minimally Invasive Model of Experimental Myocardial Infarction

The surgical technique employed to determine an experimental ischemic damage is a major factor in the subsequent process of myocardial scar development. We set out to establish a minimally invasive porcine model of myocardial infarction using cardiac contrast-enhanced magnetic resonance imaging (ce-MRI) as the basic diagnostic tool. Twenty-seven domestic pigs were randomized to either temporary or permanent occlusion of the left anterior descending artery (LAD). Temporary occlusion was achieved by inflation of a percutaneous balloon in the left anterior descending artery directly beyond the second diagonal branch. Occlusion was maintained for 30 or 45 min, followed by reperfusion. Permanent occlusion was achieved via thrombin injection. Thirteen animals died peri- or postinterventionally due to arrhythmias. Fourteen animals survived the 30-min ischemia (four animals; group 1), the 45-min ischemia (six animals; group 2), or the permanent occlusion (4 animals; group 3). Coronary angiography and ce-MRI were performed 8 weeks after coronary occlusion to document the coronary flow grade and the size of myocardial scar tissue. The LAD was patent in all animals in groups 1 and 2, with normal TIMI flow; in group 3 animals, the LAD was totally occluded. Fibrosis of the left ventricle in group 1 (4.9 +/- A 4.4%; p = 0.008) and group 2 (9.4 +/- A 2.9%; p = 0.05) was significantly lower than in group 3 (14.5 +/- A 3.9%). Wall thickness of the ischemic area was significantly lower in group 3 versus group 1 and group 2 (2.9 +/- A 0.3, 5.9 +/- A 0.7, and 6.1 +/- A 0.7 mm; p = 0.005). The extent of late enhancement of the left ventricle was also significantly higher in group 3 (16.9 +/- A 2.1%) compared to group 1 (5.3 +/- A 5.4%; p = 0.003) and group 2 (9.7 +/- A 3.4%, p = 0.013). In conclusion, the present model of minimally invasive infarction coupled with ce-MRI may represent a useful alternative to the open chest model for studies of myocardial infarction and scar development.