Prospective evaluation of stereotactic arrhythmia radioablation for refractory ventricular tachycardia: initial clinical experience in Japan

Abstract Purpose This prospective study evaluated the 1 year safety and efficacy of stereotactic arrhythmia radioablation (STAR) delivered using the CyberKnife system for refractory ventricular tachycardia (VT) in Japanese patients, in accordance with a prespecified clinical protocol. Materials and methods Three male patients with radiofrequency catheter ablation (RFCA)-refractory VT and structural heart disease, namely hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), and ischemic cardiomyopathy (ICM), were enrolled. A single fraction of 25 Gy was delivered to the target volume defined by multimodal image fusion. The primary endpoint was the absence of Grade ≥ 3 treatment-related adverse events within 12 months. Results The primary endpoint was achieved, with no acute or subacute Grade ≥ 3 toxicities observed in any patient during the first year. Although all patients experienced a reduction in VT burden, the clinical course differed by etiology. Cases 2 (DCM) and 3 (ICM) showed typical responses, including delayed efficacy and late recurrence requiring repeat RFCA. In contrast, Case 1 (HCM), with a substantially larger target volume (133 mL), showed a rapid response but a progressive decline in left ventricular ejection fraction by myocardial scintigraphy, from 59.7% to 40.0%, during the 24 month extended follow-up. Conclusion STAR demonstrated preliminary feasibility as a noninvasive salvage therapy for refractory VT in this initial Japanese pilot experience. However, the late functional decline observed in Case 1 highlights the need for long-term follow-up and myocardium-sparing techniques for large target volumes. (jRCTs042230030).