Feasibility and safety assessment of RF double applications in very high power and short duration ablation.

Background: Very high power and short duration (vHPSD) ablation is recently used for pulmonary vein isolation. However, low first-pass isolation rates have been reported, possibly because of shallow lesion formation, necessitating deeper lesions to improve treatment outcomes.

Objective: This study aimed to confirm the safety and efficacy of double radiofrequency applications of vHPSD ablation in an in vivo beating swine heart model.

Methods: Eighteen swine were anesthetized and underwent vHPSD ablation using the QDOT-MICRO catheter at 90 W for 4 seconds, targeting a contact force of 10 g. Radiofrequency applications were performed as single application (SA) and double applications (DA) with 4-8 seconds rest intervals. Lesion surface area and volume were measured postablation.

Results: A total of 337 atrial lesions and 74 ventricular lesions were created. Both 4-6 seconds DA and 7-8 seconds DA produced significantly larger and deeper lesions than did SA, with atrial surface lengths averaging 9.0 mm for 4-6 seconds DA, 9.2 mm for 7-8 seconds DA, and 8.0 mm for SA. Transmurality was observed at 100% for 4-6 seconds and 7-8 seconds DAs, while it was 94% for SA (P = .002). Ventricular lesion metrics followed similar trends. Except for 1 event of tiny char formation during 4 seconds DA in the ventricle, neither steam pops nor char formation was observed in either the atrium or the ventricle.

Conclusion: In an in vivo swine heart model, DA with 4-6 seconds and 7-8 seconds intervals create deeper and wider lesions than does SA, suggesting its potential for clinical application in areas with thicker myocardial walls. However, DA with very short intervals may still pose a risk of excessive tissue heating.