Restraining infarct expansion preserves left ventricular geometry and function after acute anteroapical infarction

Background-Expansion of an acute myocardial infarction predicts progressive left ventricular (LV) dilatation, functional deterioration, and early deat h. This study tests the hypothesis that restraining expansion of an acute i nfarction preserves LV geometry and resting function. Methods ann Results-In 23 sheep, snares were placed around the distal left anterior descending and second diagonal coronary arteries. In 12 sheep, inf arct deformation was prevented by Marlex mesh placed over the anticipated m yocardial infarct, Snared arteries were occluded 10 to 14 days later. Seria l hemodynamic measurements and transdiaphragmatic quantitative echocardiogr ams were obtained up to 8 weeks after anteroapical infarction of 0.23 of LV mass. In sheep with mesh, circulatory hemodynamics, stroke work, and end-s ystolic elastance return to preinfarction values 1 week after infarction an d do not change subsequently. Ventricular volumes and ejection fraction do not change after the first week postinfarction. Control animals develop lar ge anteroapical ventricular aneurysms, increasing LV dilatation, and progre ssive deterioration in circulatory hemodynamics and ventricular function. A t week 8, differences in LV end-diastolic pressure, cardiac output, end-dia stolic and end-systolic volumes, ejection fraction, stroke work, and end-sy stolic elastance are significant (P<0.01) between groups. Conclusions-Preventing expansion of acute myocardial infarctions preserves LV geometry and function.