Evaluation by contrast-enhanced MR imaging of the lateral border zone in reperfused myocardial infarction in a cat model

Objective: To identify and evaluate the lateral border zone by comparing th e size and distribution of the abnormal signal area demonstrated by MR imag ing with the infarct area revealed by pathological examination in a reperfu sed myocardial infarction cat model. Materials and Methods: In eight cats, the left anterior descending coronary artery was occluded for 90 minutes, and this was followed by 90 minutes of reperfusion. EGG-triggered breath-hold turbo spin-echo T2-weighted MR imag es were initially obtained along the short axis of the heart before the adm inistration of contrast media. After the injection of Gadomer-17 and Gadoph rin-2, contrast-enhanced T1-weighted M R images were obtained for th ree ho urs. The size of the abnormal signal area seen on each image was compared w ith that of the infarct area after TTC staining. To assess ultrastructural changes in the myocardium at the infarct area, lateral border zone and norm al myocardium, electron microscopic examination was performed. Results: The high signal area seen on T2-weighted images and the enhanced a rea seen on Gadomer-17-enhanced T1WI were larger than the enhanced area on Gadophrin-2-enhanced T1WI and the infarct area revealed by TTC staining; th e difference was expressed as a percentage of the size of the total left ve ntricle mass (T2= 39.2 %; Gadomer-17 =37.25 % vs Gadophrin-2 = 29.6 %; TTC staining = 28.2 %; p < 0.05). The ultrastructural changes seen at the later al border zone were compatible with reversible myocardial damage. Conclusion: In a reperfused myocardial infarction cat model, the presence a nd size of the lateral border zone can be determined by means of Gadomer-17 - and Gadophrin-2-enhanced MR imaging.