Delayed hyperenhancement patterns in occlusive and reperfused myocardial infarcts during different healing stages

To investigate delayed hyperenhancement during different healing stages of myocardial infarct with and without reperfusion in a pig model.

Twelve pigs were studied. Six pigs were subjected to permanent right coronary artery (RCA) occlusion, and the other six were subjected to transient 90-minute RCA occlusion. In vivo MRI including first-pass perfusion and myocardial delayed enhancement (MDE) was performed at four, eight, 12, and 24 hours, and eight days after the artery occlusion. The MDE scan was repeated four times, two to 32 minutes after contrast administration.

For all six pigs without reperfusion, the four-hour MRI showed transmural perfusion defect and no delayed hyperenhancement; from eight hours on, delayed hyperenhancement appeared and its spatial extent gradually increased until it became transmural hyperenhancement at eight days. However, in all six pigs with reperfusion, hyperenhancement was present at every stage from four hours to eight days. Pathology confirmed the existence of infarct at various stages of healing irrespective of reperfusion status.

Occlusive hyperacute infarct did not exhibit any delayed hyperenhancement, which indicates that perfusion plays an important role in delayed enhancement at the hyperacute stage.