Laser welding for coronary artery anastomosis: techniques, temperature profiles, and the role of chromophores

Laser vascular anastomosis is a developing technique which aims to employ the thermal effect of laser energy to achieve tissue fusion with minimal thermal damage. The tissue temperature necessary to achieve effective bonding is debated and must be related to the mechanism of fusion. Enhanced energy absorption at the anastomosis using chromophore (CR) dyes may improve technical success. Over 300 arteriotomies in porcine coronary arteries were welded in vitro using Argon (488/5 14 nm) and Nd:YAG (1060 nm) lasers with or without chromophore. Bursting pressures under saline infusion were measured and tissue temperatures during welding recorded using infrared thermal imaging. Results were as follows. Argon - CR (mmHg) [mean (s.e.)]: 249 (28). Argon + CR: 280 (22). Nd:YAG - CR: 1 5 1 (23). Nd:YAG + CR: 27 1 (30). The use of chromophore therefore increased the weld bursting strength for both lasers but this effect was statistically significant only for the Nd:YAG (p< 0.05, oneway ANOVA). Argon welds were stronger than Nd:YAG welds (p<0.O5) but this difference lost significance when chromophore was used. All welds required temperatures of around 100 degC to be effective and was inconsistent below 80 degC. In conclusion, vascular anastomoses produced by laser can withstand suprasystolic pressures. The effect of chromophore is to improve weld strength and consistency and furthermore, to visibly reduce thermal damage and facilitate beam aiming. These are considerable technical advantages.