What is the most appropriate energy source for aortic cusp ablation? A comparison of standard RF, cooled-tip RF and cryothermal ablation

Background: Certain tachycardias can be eliminated by catheter ablation from within the base of the aortic valve (AV) cusps but the high blood flow and proximity to the coronary arteries create unique challenges. Standard radiofrequency (RF) energy, cooled-tip RF energy or cryothermal energy were compared to determine the optimal ablation modality. Materials and methods: Experiments were conducted using adult swine or goats (15 animals). Ablation lesions were placed using either: temperature-controlled RF (4 mm-tip catheter; 60°C/60 s), cooled-tip RF (4 mm-tip catheter with internal saline circulation at 0.6 ml/s; 40°C/60 s), or cryoablation (6 mm-tip spot cryocatheter; <-75°C/4 min). Animals were sacrificed 1 h after the last application and lesions were subject to pathological analysis. Results: Standard RF and cryoablation created similar depth lesions in the right coronary cusp (4.2±1.3 and 3.4±0.5 mm, respectively) but cryoablation was unable to create any visible lesions in the non-coronary cusp. Cooled tip ablation created larger ablation lesions in the right coronary cusp (5.25±0.5) and fully transmural left atrial ablation lesions after ablation in the noncoronary cusp. Acute damage to the cusps was not noted with any ablation modality. Disruption of elastic fibers in the aortic media was seen after standard and cooled tip radiofrequency ablation but not cryoablation. Conclusion: Cryoablation within the AV cusps created similar sized lesions to standard RF ablation without evidence of elastic fibre disruption and may therefore be an appropriate first line ablation modality. Cooled-tip ablation created larger ablation lesions and therefore may be required if cryoablation is ineffective.