Background: The radio-frequency catheter ablation (RFCA) therapy has 3 Achilles’ heels caused by the joule heat as an energy source. First, limited lesion depth due to heat transfer results in ineffectiveness for the treatment of ventricular arrhythmias of epicardial origin. Second, myoendocardial injury causes resultant thromboembolic complications. Third, post-procedural inflammation responses are sustained with subsequent early phase recurrences. In order to overcome these limitations of RFCA, we have been developing a shock wave catheter ablation (SWCA) system as a novel non-thermal therapy (Fig. A). We have previously demonstrated that we are able to create persistent AV block in pigs in vivo with a prototype catheter. In this study, we further examined the lesion effects of the SWCA.
Methods and Results: We applied the newly-improved SWCA system to ventricular muscle of pigs in vivo. A total of 22 pigs were used for the following 3 protocols. (1) Epicardial approach: the lesion depth by the SW application from the epicardium was examined in 7 pigs (total 35 points applications). Average lesion depth achieved was 5.2±0.9 (SD) mm (the maximum 8 mm), which was equal to or greater than RFCA lesion depth. (2) Endocardial approach: the difference in the extent of superficial injury between the 2 energy sources was examined in 6 pigs (8 points each) by scanning electron microscope (SEM). SWCA caused markedly reduced myoendothelial injury compared with RFCA (4.3±1.2 vs 79.6±4.8%) (P<0.01) (Fig. B). (3) The time-course of SW-induced myocardial lesions was examined in 9 pigs. We found that in the SWCA lesions, inflammatory responses were transient (~4 days) and reparative process was accelerated with preserved blood flow. Furthermore, the extent of myocardial angiogenesis was enhanced in the SWCA lesions compared with the RFCA lesions (Fig. C, D).
Conclusion: Our SWCA system may be superior to RFCA in terms of lesion depth, myoendocardial injury and tissue repair process.