Noninvasive stereotactic radiosurgery (CyberHeart) for creation of ablation lesions in the atrium.

BACKGROUND: A variety of catheter-based energy modalities are used for cardiac ablation to treat arrhythmias. Robotic radiosurgery is increasingly being utilized to successfully accomplish precise tissue ablation in anatomically remote areas. OBJECTIVE: The purpose of this study was to examine the experimental feasibility of a noninvasive method using stereotactic robotic radiosurgery (SRS) to create cardiac lesions. METHODS: Sixteen (16) Hanford-Sinclair mini swine (weight 40-70 kg) under general anesthesia were studied. Baseline computed tomographic scans were performed, followed by electroanatomic mapping using the CARTO system. Stereotactic robotic radiosurgery was performed using the CyberHeart system, with predetermined targets at the cavotricuspid isthmus, AV node, pulmonary vein-left atrial junction, or left atrial appendage. From 25 to 196 days after treatment, the animals were investigated with repeat electroanatomic voltage mapping and transesophageal echocardiography, when possible. The animals then were sacrificed and pathology specimens taken. RESULTS: Dose ranging suggested that 25 Gy was needed to produce an electrophysiologic effect. The time course showed an electrophysiologic effect consistently by 90 days. The method was feasible for producing bidirectional cavotricuspid isthmus block and AV nodal conduction block. The pulmonary vein-left atrial junction and left atrial appendage showed marked voltage reduction to less than 0.05 mV. No spontaneous arrhythmias were observed. Pathology specimens showed no evidence of radiation damage outside the target. Histology samples from target sites showed effects consistent with X-beam radiation. CONCLUSION: Stereotactic robotic radiosurgery can produce cavotricuspid isthmus block, AV nodal block, and significant decreased voltage at the pulmonary vein-left atrial junction. No other organ damage was seen. The study findings demonstrate the feasibility of this noninvasive treatment method for creating cardiac lesions. This approach merits further investigation in the treatment of arrhythmias.