Abstract Body (Do not enter title and authors here): Background:
Ventricular tachycardia (VT) associated with ischemic (ICM) and non-ischemic cardiomyopathy (NICM) presents distinct substrate patterns, influencing mapping and ablation strategies. Stereotactic body radiotherapy (SBRT) has emerged as a novel salvage therapy for VT refractory to antiarrhythmic drugs (AADs) and catheter ablation.

Objective:
To compare clinical characteristics, treatment parameters, and outcomes following SBRT for VT in patients with ICM versus NICM.

Methods:
We performed a retrospective analysis of 45 consecutive patients treated with single-fraction SBRT (25 Gy) for drug- and ablation-refractory VT at a tertiary care center. Baseline characteristics, treatment volumes, VT recurrence, and clinical outcomes were compared between ICM and NICM groups. Cox proportional hazards regression was used for survival analysis.

Results:
Of the 45 patients, 24 (53%) had ICM and 21 (47%) had NICM. NICM patients were younger (65 vs. 73 years, p = 0.004), had lower baseline ejection fraction (12% vs. 26%, p = 0.03), and were more likely to be female (p = 0.04). Coronary artery disease was present in all ICM patients compared to 24% of NICM patients (p < 0.001). Despite these baseline differences, treatment volumes (PTV, ITV, GTV) and SBRT target locations were similar between groups. Recurrent VT post-SBRT was common in both groups (75% ICM vs. 81% NICM, p = 0.63), with no significant difference in time to recurrence, repeat ablations, or ICD shocks. Mortality and progression to advanced therapies such as transplant or LVAD implantation did not differ significantly between groups (Figure).

Conclusion:
Despite marked differences in baseline clinical profiles, outcomes following SBRT for refractory VT—including arrhythmia recurrence, need for re-ablation, and mortality—were similar between patients with ICM and NICM. These findings support the use of SBRT as a viable treatment option regardless of cardiomyopathy subtype.