A 71-year-old man with coronary artery disease, coronary artery bypass grafting in 2000, baseline ejection fraction of 0.24, and implantation of a single chamber implanted cardioverter defibrillator (ICD) in 2009 for ventricular tachycardia (VT) presented with continuous episodes of nonsustained and sustained VT refractory to sotalol and mexiletine. Despite angioplasty and stent for coronary artery disease, VT continued for 2 years. Medical history included atrial fibrillation and oxygen-dependent chronic obstructive pulmonary disease. Baseline electrocardiogram (ECG) showed atrial fibrillation with a ventricular rate of 82 beats per minute with inferior Q waves and QRS duration of 90 ms. Twelve-lead ECG during VT showed a regular, wide-complex tachycardia at 160 beats per minute (CL 380-400 ms), with a right bundle branch block pattern, superior axis, precordial transition at V3-V4. His ICD log showed numerous VT episodes, with a single morphology seen on intracardiac ventricular electrogram, cycle length 380-411ms. Episodes were nonsustained, pace-terminated, and shock-terminated. As catheter ablation was relatively medically contraindicated, he consented to a Food and Drug Administration and Institutional Review Board-approved compassionate-use protocol of stereotactic arrhythmia radioablation (STAR), noninvasive ablation of VT substrate by stereotactic ablative radiotherapy (SABR) techniques for tumors. STAR therapy was delivered in October, 2012. STAR Planning and DeliveryBaseline echocardiogram showed a dilated left ventricle (LV), ejection fraction of 0.24, with basal inferior aneurysm, and apical and infero-posterior akinesis. Positron emission tomography-computed tomography showed extensive hypometabolic scar in the LV extending between the LV base and the apex, involving the inferior, inferoseptal, and inferolateral walls. A target for STAR was delineated using proprietary visualization and contouring software (CardioPlan™, CyberHeart™, Portola Valley, CA), outlining the target volume corresponding to what would have been the likely catheter ablation volume for this VT substrate based on imaging-defined inferior LV scar and 12-lead ECG QRS morphology during VT, implying a likely inferior LV VT circuit location ( Figure 1A). The target volume was transferred to the radiation treatment planning software (MultiPlan 4.6.0, Accuray, Sunnyvale, CA) of the treatment system (CyberKnife®, Accuray, Sunnyvale, CA), with normal organs delineated, including lungs, esophagus, and stomach.A temporary pacing wire (Oscor, Inc., Miami Lakes, FL) was fluoroscopically placed in the RV apex as an imaging fiducial marker that could be dynamically tracked to compensate for respiratory motion (Synchrony® Respiratory Tracking 9.6.0, Accuray, Sunnyvale, CA). The magnitude of the remaining cardiac motion was determined by fluoroscopy of the fiducial marker during transient breath holds, and the final target volume included an expansion to encompass this residual motion. The finalized target was then used for treatment planning.A...

Background: Stereotactic radiosurgery is a form of radiotherapy that is performed in a single session and focuses high-dose ionizing radiation beams from a collimated radiation source to a small, localized area of the body. Recently, stereotactic radiosurgery has been applied to arrhythmias (stereotactic arrhythmia radioablation - STAR), with promising results reported in patients with refractory, scar-related ventricular tachycardia (VT), a cohort with known high morbidity and mortality. Objective: Herein, we describe our experience with the use of CyberKnife, a frameless image-guided linear accelerator stereotactic radiosurgery system, in conjunction with CardioPlan, a cardiac specific radiotherapy planning software, to treat patients with scar-related VT, detailing its early and mid- to long-term results. Methods: This is a pilot, prospective study of patients undergoing STAR for refractory VT. The anatomical target for radioablation was defined based on the clinical VT morphology, electroanatomical mapping, and study-specific pre-procedural imaging with cardiac computed tomography. The target volume delineated with the aid of CardioPlan was treated with a prescription radiation dose of 25 Gy delivered in a single fraction by CyberKnife in an outpatient setting. Ventricular arrhythmias and radiation-related adverse events were monitored at follow-up to determine STAR efficacy and safety. Result: Five patients (100 % male, 63 ± 12 years old, 80 % ischemic cardiomyopathy, left ventricular ejection fraction 34 ± 15 %) with refractory VT underwent STAR between January and June 2018. Radioablation was delivered in 82 ± 11 minutes without acute complications. During a mean follow-up of 12 ± 2 months, all patients experienced clinically significant mid- to late-term ventricular arrhythmia recurrence; two patients died of complications associated with their advanced heart failure. There were no clinical or imaging evidence of radiation necrosis or other radiation-induced complications in the organs at risk surrounding the scar targeted by radioablation. Conclusion: Despite good initial results, STAR did not result in effective ventricular arrhythmia control in the long term in a selected, high-risk population of patients with scar-related VT. The safety profile was confirmed to be favorable, with no radiation-related complications observed during follow-up. Further studies are needed to explain these disappointing results.

doi: medRxiv preprint NOTE: This preprint reports new research that has not been certified by peer review and should not be used to guide clinical practice.

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