Acute effects of laser myocardial ablation in <i>ex vivo</i> and <i>in vivo</i>

Abstract

Aim. To study and compare the lesions characteristics of laser energy in heart ex vivo and in experimental large animals.Materials and methods. For the ex vivo experiment a pig heart was obtained from a local slaughterhouse. Laser applications were applied using power 15-30 W in the left and right ventricles 5-50 seconds in duration. Immediately after ablation, examination was performed to determine myocardial damage characteristics at each point. In the experimental study, 7 sheep were included, laser applications were performed under fluoroscopic control in the right atrium with power 10, 15 and 20 W, 10-25 s; in the right ventricle 20, 25 and 30 W for 10-40 s; and in the left ventricle 20, 25 and 30 W for 20-40 s. The animals were euthanized and macroscopic examination of laser lesions was performed.Results. A total of 27 laser applications were performed on the heart ex vivo, all lesions were visualized as white spots on the endocardial surface. The maximum lesion depth was 9 mm achieved when using 20 W /50 s, the maximum lesion diameter was 6 mm, when using 25 W /40 s. The minimum lesion diameter and depth were observed when using 30 W /5 s, 2x1 mm. A total of 48 laser applications were performed in experimental animals, in one experimental animal was observed a transmural lesion in the right atrium when using 15 W /20 s. In 3 out of 7 experimental animals, transmural lesions were observed in the right ventricle when using 20 W /30 s; 20 W /40 s and 30 W /10 s. In the left ventricle, transmural lesions were observed in 2 animals, using 15 W /20 s and 20 W /40 s. In the ex vivo study, there was a strong positive correlation between ablation energy and lesion depth (R=0.91, P<0.05) and lesion volume (R=0.73, P<0.05); while there was no such statistical correlation in vivo.Conclusions. Laser ablation 15-20 W for 15-40 s seems to be optimal for achieving the deepest lesions in the atrium and ventricular myocardium. In our small pilot study with fiberoptic catheter ablation on a beating heart there was no correlation between energy delivered and the depth and volume of necrotic myocardium.