Safety and efficacy of stereotactic arrhythmia radioablation for ventricular arrhythmias using a novel multimodal fusion workflow for target delineation

Stereotactic arrhythmia radioablation (STAR) has emerged as a treatment for refractory ventricular tachycardia (VT), showing significant arrhythmia reduction and promising safety profile. Challenges remain, such as precise target determination and delineation. We aimed to evaluate the clinical safety and efficacy of STAR using a workflow for multimodal data integration and target delineation.

Patients undergoing cardiac STAR with a C-arm linear accelerator for refractory VT since 2022 were treated using multimodal workflow integrating multiphase contrast-enhanced ECG-gated cardiac computed tomography (CT), respiration-correlated 4D-CT, multimodal imaging data (late gadolinium enhancement from cardiac magnetic resonance imaging or positron emission tomography scan) and electroanatomical mapping from prior ablation procedures. The primary endpoint was the rate of appropriate ICD therapies comparing the 12-month period before and after STAR, with a 6-week blanking period after treatment to allow for a treatment effect.

From October 2021 to July 2024, 14 patients (74.9±8.5 yo, all men) were treated using this multimodal imaging delineation software. The underlying cardiomyopathy included ischemic (n=6), primary dilated (n=6), hypertrophic (n=1) and arrhythmogenic right ventricular cardiomyopathy (n=1). The median number of appropriate ICD therapies during the 12 months before STAR was 23.5 [19.0-53.0], including 11.0 [1.0-35.0] ATPs and 7.5 [3.0-12.0] shocks. All but one patient had prior catheter ablations, with 3D maps from these procedures integrated into the planning software.

The mean volumes of the Card-TV and PTV were 23.4±8.5 cc (9.0 to 44.8) and 92.6±27.6 cc (45.1 to 142.7), respectively. A dose of 25 and 20 Gy weas delivered in 8 (64.3%) and 5 (35.7%) patients, respectively. Treatment duration was 29.7±6.1 min. The doses covering 50% and 95% of the PTVs were 21.1±2.1 and 24.4±4.6 Gy, respectively. Of the 14 patients, 13 were safely discharged, with one patient succumbing to a lung infection following electrical storm. During the initial 6-week blanking period, 4 (28.6%) patients had VT recurrences.

Among the 13 patients safely discharged, 5 (35.7%) did not have any VT recurrence after a median follow-up of 12 months, and all but 3 patients had less arrhythmias the year after STAR compared to the previous year (Panel B and C). Overall, appropriate therapies decreased significantly to 1.5 [0.0-6.0] (p=0.013, panel D), including 0.0 [0.0-3.0] ATPs (p=0.091, panel E), and 0.0 [0.0-2.0] shocks (p<0.001, panel F). Three patients died from unrelated causes (cancer, frailty, or unknown reasons), and no serious adverse events directly related to STAR were observed.

Multimodal fusion workflow for target delineation is useful to ensure STAR efficiency, leading to a significant decrease in arrhythmia burden over follow-up, with an excellent safety profile.