CHANNEL PATENCY AND NEOVASCULARIZATION AFTER TRANSMYOCARDIAL REVASCULARIZATION USING AN EXCIMER-LASER - RESULTS AND COMPARISONS TO NONLASEDCHANNELS

Background Transmyocardial revascularization (TMR) has emerged as a pr omising treatment for ischemic heart disease in patients who are not c andidates for coronary bypass surgery or angioplasty. Controversy exis ts, however, as to whether the use of laser energy is critical for TMR channel patency. We therefore compared by histologic assessment the o utcome of lased channels with nonlased channels 30 days after TMR, usi ng a low energy, short-pulse, fiberoptic excimer laser. Methods and Re sults In each of six sheep, 36 l-mm TMR channels (9 mJ; 240 Hz; 1.55 c m advance/s) were placed in the anterior wall of the left ventricle, a nd 12 l-mm nonlased channels were created in adjacent segments by adva ncing the fiberoptic through the left ventricular wall with the laser inactivated. Of the 36 lased channels, 56 +/- 7.3% were identifiable, and 100% of those identifiable appeared to represent a ''channel deriv ative'' with evidence of an endothelialized lumen, whereas none of the nonlased channels had evidence of channel patency. Lased channels had a marked neovascular response (graded on a 0-3 scale) compared with n onlased channels (2.5 +/- 0.1 versus 1.0 +/- 0.1; P<.05). Echocardiogr aphy performed 1 and 30 days after TMR demonstrated normal global and regional left ventricular function in all animals. Creatinine phosphok inase myocardial band fractions were not significantly increased after TMR. Conclusions TMR using the excimer laser results in increased evi dence of channel derivatives and neovascularization compared with nonl ased channels while preserving normal ventricular function. These find ings suggest that laser energy may be an important component of TMR st rategy.