Abstract 2246: <i>Non-invasive</i> ablation of the Left Superior Pulmonary Vein-Left Atrial junction using stereotactic focussed radiation

Abstract

Introduction: High energy x-ray irradiation from a linear accelerator mounted on a robot arm has recently been used to produce ablation of cardiac tissue in swine. This device is currently used in patients for diverse indications requiring careful targeting, from tumors to trigeminal neuralgia. Purpose: This study was to determine if this method of energy delivery can be used to target potential arrhythmogenic sites such as the left superior pulmonary vein-left atrial junction. Method: Hanford-Sinclair mini-swine (40–70kg)(n=9) were studied under anesthesia. The animals underwent radiation (x-rays, 20 – 80 Gray) using a computer controlled robotic arm (Cyberknife) which focussed the x-ray beam on a preselected target. Targeting was done using either surgically implanted fiducials or fully non-invasively using a CT scan. A proprietary system was used to radiate the target while minimizing the dose to surrounding structures. Motion compensation was made for respiration during radiation, but no cardiac contractile motion compensation was made. The animals were then studied 4 – 8 weeks later with construction of cardiac voltage maps using CARTO (Biosense-Webster). Following this the animals were sacrificed and specimens taken for pathology. Results: All animals survived treatment. Radiation to the left superior pulmonary vein eliminated local electrograms with voltage less than 0.1mv. Pathology specimens showed histologic changes consistent with an area of discrete myocyte damage. There was no evidence of phrenic nerve injury. Limitations: This study was done in swine and human pulmonary vein response to this treatment is unknown. This model was arrhythmia free and the efficacy of this treatment for atrial fibrillation is unknown. Conclusions: Selective targeting of cardiac arrhythmogenic sites can be done using stereotactically focussed external radiation with respiratory motion compensation. The left superior pulmonary vein can be ablated without compensation for cardiac contractility.