TRANSMYOCARDIAL LASER REVASCULARIZATION FAILS TO PREVENT LEFT-VENTRICULAR FUNCTIONAL DETERIORATION AND ANEURYSM FORMATION AFTER ACUTE MYOCARDIAL-INFARCTION IN SHEEP

Objective: Transmyocardial laser revascularization is an investigation al technique for revascularizing ischemic myocardium in patients with inoperable coronary arterial disease. This study tests the hypothesis that laser revascularization prevents left ventricular functional dete rioration and aneurysm formation after acute anteroapical myocardial i nfarction, Methods: An ultrasonic ascending aortic flow probe and snar es around the distal left anterior descending and second diagonal coro nary arteries were placed in 26 Dorsett hybrid sheep. Ten to 14 days l ater, snared arteries were occluded to produce an anteroapical infarct ion of 23% of left ventricular mass. Before infarction 14 animals had 34 +/- 4 transmyocardial perforations in the area of the anticipated i nfarction made with a carbon dioxide laser. Twelve animals served as c ontrols. Hemodynamic measurements and transdiaphragmatic quantitative echocardiograms were obtained before, immediately after, and 2, 5, and 8 weeks after infarction, Eighteen sheep completed the protocol. Resu lts: All animals had large anteroapical left ventricular aneurysms wit h massive ventricular enlargement. Immediately after infarction the an terior wall became thinner and dyskinetic in all sheep. At 8 weeks ane urysmal size and shape were indistinguishable between groups. Two days after infarction, laser holes were filled with fibrin, At 5 and 8 wee ks the infarct consisted of dense collagen, fibroblasts, scattered cal cifications, myocyte fragments, neutrophils, macrophages, and no laser holes, There were no significant differences at any time between grou ps for cardiac pressures or output, ventricular volumes, ejection frac tion, stroke work, and the stroke work-left ventricular end-diastolic pressure index., Conclusion: Transmyocardial laser perforations do not revascularize acute myocardial infarction in sheep.