Development of a novel shock wave catheter ablation system-A validation study in pigs in vivo.

Aims: Although the radiofrequency catheter ablation (RFCA) is widely used for the treatment of tachyarrhythmias, it has three fundamental weaknesses as a thermal ablation system, including a limited lesion depth, myoendocardial injury linking to thromboembolism, and prolonged inflammation followed by subsequent recurrences. In order to overcome these limitations, we have been developing a shock wave (SW) catheter ablation (SWCA) system as a novel non-thermal therapy. In the present study, we validated our new SWCA system with increased SW intensity. Methods and results: In a total of 36 pigs, we applied our new SWCA to ventricular muscle in vivo for the following protocols. (i) Epicardial approach (n = 17): The lesion depth achieved by the SWCA from the epicardium was examined. High intensity SW achieved 5.2 ± 0.9 mm lesions (35 applications), where there was a strong correlation between SW intensity and lesion depth (R = 0.80, P < 0.001, 54 applications). (ii) Endocardial approach (n = 6): The extent of endocardial injury with the two energy sources was examined by electron microscopy (8 applications each). Shock wave catheter ablation markedly reduced myoendothelial injury compared with RFCA (4.3 ± 1.2 vs. 79.6 ± 4.8%, P < 0.01). The electrophysiological effects on the SW lesions were also confirmed using three-dimensional mapping system. (iii) Time-course study (n = 6 each): The healing process after ablation therapy was examined. We found transient inflammatory responses and accelerated reparative process with preserved blood flow in the SWCA group. Conclusion: These results indicate that our SWCA system is characterized, as compared with RFCA, by deeper lesion depth, markedly less myoendocardial injury and accelerated tissue repair process.