Stereotactic Cardiac Radiotherapy Reduces Structural Heart Disease Associated Refractory Ventricular Tachycardia - A Metaanalysis

Introduction: Cardiac stereotactic body radiotherapy (SBRT) is a paradigm changing treatment for refractory ventricular tachycardia (VT) in patients with structural heart disease. We sought to review the effectiveness of SBRT reported in published studies. Hypothesis: There is a reduction in VT events after cardiac SBRT. Methods: We performed a comprehensive literature search in PubMed, Embase and Google Scholar including all studies on cardiac SBRT for VT till May 2022. Efficacy was evaluated as random-effects pooled rate ratios (RR) of VT episodes, antitachycardia pacing (ATP) therapies and implantable cardioverter-defibrillator (ICD) shocks post-SBRT (after 6-week blanking) vs. during 3-12 months pre-SBRT, with patients serving as their own controls. Results: We included 12 single-arm studies on cardiac SBRT (90 patients) published 2017-2022 with median follow-up ranging 6-28 months. The pooled RR of VT episodes, ATP therapies and ICD shocks post- vs. pre-SBRT were 0.11 (95% CI 0.06-0.21, p<0.001), 0.09 (95% CI 0.04-0.20, p<0.001), and 0.10 (95% CI 0.05-0.19, p<0.001) as shown in Figure 1. There was significant heterogeneity in results (p<0.00001 for all 3 endpoints). The combined 1- and 2-year overall patient survival was 69% and 56% respectively (Figure 2). Conclusions: Cardiac SBRT reduces recurrent VT episodes and ICD shocks in patients with VT refractory to medical therapy and catheter ablation. There is heterogeneity in results from different studies, likely related to differences in patient selection and treatment techniques. The overall patient survival in this high-risk population compares favorably to data from catheter ablation trials.