Acute effects of laser myocardial ablation in ex vivo and in vivo

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.

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