MYOCARDIAL COAGULATION BY INTRAOPERATIVE ND-YAG LASER-ABLATION AND ITS DEPENDENCE ON BLOOD PERFUSION

To investigate whether the efficacy of intraoperative laser ablation t herapy is affected by myocardial blood perfusion, we irradiated 11 can ine hearts through the epicardium with a Nd:YAG laser (10, 20, and 30 J/mm(2)) using air as the medium. Compared coagulated myocardial depth , width, and volume obtained in the red beating heart was compared wit h those in the white nonbeating heart infused with 0 degrees C saline (cardioplegic model) via the coronary artery. Histologically, the macr o- and microscopical findings were very similar. At each level of ener gy, the width and volume of red myocardium coagulated were significant ly larger than those of white myocardium (P < 0.01). At 30 J/mm(2), th e depth of coagulation of red myocardium was significantly larger than that of white myocardium (P < 0.01). The coagulated volume of the whi te myocardium was about 60% of that of the red myocardium. Nd:YAG lase r energy was absorbed by blood (red color = hemoglobin), and more ener gy tvas transferred in the higher temperature myocardium. During intra operative Nd:YAG laser ablation, the presence of blood perfusion in ca rdiac tissue is thought to be an important factor affecting safe irrad iation.