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Education: Minimally Invasive Cardiac Arrhythmia Ablation: Use of Radiosurgery Education: Minimally Invasive Cardiac Arrhythmia Ablation: Use of Radiosurgery Patrick Maguire, MD, PhD and Thomas Fogarty, MD CyberHeart Incorporated, Portola Valley, California Stanford University, Stanford, California. USA Ablaon of cardiac arrhythmias has progressed over the last decade and the technology is now accepted and ulized internaonally. A variety of energy sources are used including radiofrequency, cryothermy, laser energy, etc., all with varying degrees of success. Most current therapies are catheter based and involve the use of sophisticated techniques, including intra-cardiac manipulation of catheters by experienced clinicians. Improvements in outcomes are noted, yet long term relief of arrhythmia in the case of atrial fibrillaon and ventricular tachycardia is elusive. New ablaon technology (radiosurgery), used inially in the field of oncology, is minimally invasive, and can provides accurate placement of beam energy that is guided by imaging. Ablaon lesions can be created even in consideraon of target moon. 1,2 Secondly, the energy delivery is highly focused so as to minimize any possible long term radiaon effect on other structures nearby. Radiosurgery has been previously used to treat the heart, albeit in oncology applications (tumors metastac to the heart). 3,4 CyberHeart Inc. (Portola Valley, CA) has developed 3-D treatment planning soſtware and technology to allow the precise targeting and delivery of ablation to anatomic targets associated with arrhythmia. 5 The concept of this non- to minimally invasive energy delivery is intriguing, and has the potential to reduce patient procedural risk, reduce peri-procedural discomfort and achieve equivalent efficacy. The technology involves use of a radiosurgery system, such as the Cyberknife© (Accuray Inc., Sunnyvale, CA) that has the ability to plan accurate radiation dose delivery (<1.5 mm accu- racy with moon) and subsequent energy delivery. The addion of three-dimensional cardiac planning software enables this technology to ablate the myocardium in a precise fashion. Figure 1 shows the instrument and patient set-up. The enabling soft- ware (CardioPlan®, CyberHeart, Portola Valley, CA) gives the planning clinician the ability to: 1- direct ablaon volume placement; 2- examine the placement of dose relative to nearby structures to preserve safety; and 3-visualize this in 3-dimensions before ever treating the patient. (Figure 2). Once a target volume has been constructed, other or- gans can be ‘protected’ by not allowing energy beams to traverse while being directed at the clinical target volume. (Figure 3). Figure 1. Typical room set-up of the cyberknife radiosurgery Figure 2. Panel to the right demonstrates the target (blue line) of the proposed ablaon plan to create pulmonary vein isolaon in 3-D. One can see the relaonship of dose (red) to the other crical structures, such as esophagus (green) and bronchi (light blue). Panel on the leſt shows this treatment plan translated to the 2-D CT scan.
