The vascular response induced by transmyocardial laser revascularization is determined by the size of the channel scar: Results of CO2, holmium and excimer lasers.

Background and Objectives: To investigate the angiogenic effect Of CO2, Ho:YSGG, and XeCl excimer TMLR in a rat model with morphologic characteristics of chronic myocardial ischemia. Study Design/Materials and Methods: Two channels (200-320 mum) were created per rat heart. After 14 days, vessel numbers and densities in and around laser scars were assessed. Results: Capillary densities in the laser scars were equal between the three lasers (similar to130 vessels/mm(2)) but much lower than in control areas (similar to2,100 vessels/mm(2)). Vessel densities excluding capillaries were significantly higher in Ho:YSGG and CO2 scars compared to excimer scars, while only Ho:YSGG scars contained significantly more large vessels (diameter > 20 mum) than control areas. Only rarely, extension of vascular growth into adjacent myocardium was observed in any of the three groups. Conclusions: These results indicate that the angiogenic response following TMLR is limited to the channel scar and related to the scar size rather than the specific laser type. (C) 2004 Wiley-Liss, Inc.