Induction of angiogenesis after TMR: A comparison of holmium : YAG, CO2, and excimer lasers

Background. Transmyocardial laser revascularization (TMR) is an emerging tr eatment for end-stage coronary artery disease. A variety of lasers are curr ently available to perform the procedure, although their relative efficacy is unknown. The purpose of this study was to compare changes in myocardial blood now and function 6 months after TMR with holmium:yttrium-aluminum-gar net (holmium:YAG), carbon dioxide (CO2), and xenon chloride excimer lasers in a model of chronic ischemia. Methods. Miniswine underwent subtotal (90%) left circumflex coronary stenos is. Baseline positron emission tomography and dobutamine stress echocardiog raphy were performed to document hibernating myocardium in the left circumf lex coronary artery distribution. Animals were then randomized to sham redo -thoracotomy (n = 5) or TMR using a holmium:YAG (n 5), CO2 (n = 5) or excim er (n = 5) laser. Six months postoperatively, the positron emission tomogra phy and dobutamine stress echocardiography studies were repeated and the an imals sacrificed. Results. In animals undergoing TMR with holmium: YAG and CO, lasers, a sign ificant improvement in myocardial blood flow to the lased left circumflex r egions was seen. No significant change in myocardial blood now was seen in sham- or excimer-lased animals. There was a significant improvement in regi onal stress function of the lased segments 6 months postoperatively in anim als undergoing holmium:YAG and CO2 laser TMR that tvas consistent with a re duction in ischemia. There was no change in wall motion in sham- or excimer -lased animals. Significantly greater neovascularization was observed in th e holmium:YAG and CO2 lased regions than with either the sham procedure or excimer TMR. Conclusions. Transmyocardial laser revascularization with either holmium:YA G or CO2 laser improves myocardial blood flow and contractile reserve in la sed regions 6 months postoperatively. These changes were not seen following excimer TMR or sham thoracotomy, suggesting that differences in laser ener gy or wavelength or both may be important in the induction of angiogenesis. (C) 2000 by The Society of Thoracic Surgeons.