PREVENTION OF ACUTE REGIONAL ISCHEMIA WITH ENDOCARDIAL LASER CHANNELS

Laser myocardial revascularization has been shown to reduce mortality and infarct size after left anterior descending coronary artery (LAD) ligation in dogs. It has not been shown to improve myocardial contract ility in acute ischemia. In this study a holmium-yttrium-aluminum garn et laser (wavelength, 2.14 mum) was used to create nontransmural myoca rdial channels from the endocardial surface in the ischemic regions of the canine left ventricle. Twelve mongrel dogs (6 controls, 6 laser m yocardial revascularizations) underwent 90 minutes of LAD ligation fol lowed by 6 hours of reperfusion. The ischemic region was determined by methylene blue injection during brief LAD occlusion. Laser myocardial revascularization averaged three channels per square centimeter in th e ischemic region created using 12 J/channel (600 mJ/pulse, 10 Hz) bef ore LAD ligation. Contractility was assessed from regional preload rec ruitable stroke work (RPRSW), using pairs of segment length ultrasonic transducers in the ischemic and the nonischemic regions. Two-dimensio nal echocardiography corroborated with segmental length findings. In c ontrol dogs, the ischemic region was dyskinetic during LAD ligation an d reperfusion. Dyskinesis of the ischemic region during systole produc ed negative values for regional stroke work, and RPRSW was considered zero. In 4 of 6 laser-revascularized dogs, RPRSW remained positive in the ischemic region. Two dogs had intermittent dyskinesis. The differe nce between laser-revascularized and control dogs in ischemic region R PRSW was significant (p < 0.01 by Fischer's exact test). We conclude t hat laser myocardial revascularization from the endocardial surface pr eserves regional myocardial function during acute ischemia. Because ho lmium-yttrium-aluminum garnet laser energy can be transmitted through a flexible fiber, laser myocardial revascularization could become a pe rcutaneous treatment for prevention of acute ischemia.