Arrhythmia Ablation Using Pencil Beam Scanned Carbon Ions in a Porcine Model: First Data from the 12C for Catheter-free Ablation Study

ntroduction: Accelerated carbon ions (12C) are rigorously accurate and effective in cancer therapy. This study investigates scanned 12C particle therapy, as modality for precise catheterfree ablation. Methods: Eighteen pigs were randomized to irradiation of AV node (AVN), LA-PV junction (PVI), freewall LV, and shamAVN. EA mapping, fiducial marker placement, and pacemaker implantation (AVN only) were performed. PVI and LV were targeted using 40 Gy. AVN was targeted with 25, 40, and55 Gy. Cardiac gated CTs (1 mm voxel and slice spacing) were obtained during breath-hold at expiration. Targets were contoured and case-specifically expanded to cover motion. For positioning, X-rays were used. 12C was delivered using rescanned raster pencil-beams. Animals are followed for up to 6 months (ongoing) with extensive analyses. Results: Fifteen pigs were irradiated (weight 33.8 ± 3.5 kg) using a horizontal beam line, bilaterally entering the chest. For AVN ablation a volume of 1.8 ± 0.1 cc was irradiated with target dose. For PVI and LV, mean volumes were 14.9 ± 1.8 cc and 2.4 ± 0.3 cc, respectively. Risk structures were spared. Animals stayed in SR during irradiation. In-beam positron-emissiontomography confirmed precise beam delivery. After 13 weeks, ICE revealed hyperechoic LV myocardium in the target zone (Fig. A). EA mapping showed abnormal epicardial potentials with non-transmural fibrosis present in the target location (Fig. B). Complete AV block developed over the course of 4 months in 40 and 55 Gy animals. No radiation-related side effects were observed. Conclusions: 12C particle therapy is a new means for catheterfree arrhythmia elimination that yields tremendous potential.