(P143) STEREOTACTIC BODY RADIOABLATION THERAPY TO TARGET VENTRICULAR TACHYCARDIA ORIGINATING FROM THE ANTEROLATERAL PAPILLARY MUSCLE WITH : A SINGLE CENTRE EXPERIENCE

Background: Ventricular Tachycardia (VT) is prevalent in the setting of non-ischemic cardiomyopathy (NICM), with recurrence rates as high as 58% after catheter ablation. Stereotactic body radioablation therapy (SBRT) involves precise delivery of radiation to arrhythmogenic substrates, and represents a novel approach to reduce recurrent implantable cardioverter defibrillator (ICD) therapies in patients with refractory VT. Though SBRT has shown preliminary effectiveness in reducing VT episodes, its effectiveness in NICM patients has not been widely evaluated.

METHODS AND RESULTS: This research evaluated SBRT effectiveness in NICM patients with scars at the basal anterolateral papillary muscle at a tertiary care center between November-December 2022. Eligible patients had their VT substrate mapped using a single-use ECGI vest and a 4D-CT simulation scan. MRI scans were used to aid anatomical identification of the anterolateral papillary muscle which could not be seen on the non-contrast diagnostic CTs. SBRT was delivered in a single fraction of 25 Gy under image guidance. SBRT effectiveness was evaluated as changes in frequencies of total antitachycardia pacing (ATP) and ICD shock episodes from 6 months pre-, and within 3, 6, and 12 months post SBRT. Participants were 3 males with NICM, aged 56, 60, and 73 with previous dual chamber ICD implantation, 2 of whom had a history of VT ablation/ VT storm and paroxysmal atrial fibrillation. All participants had basal lateral scar, and were receiving beta blockers, mexiletine, and amiodarone with refractory VT before SBRT. Prior to SBRT, ICD interrogation showed a total of 119 (77, 7, and 35 in patients 1-3 respectively) ATPs, and 27 (10, 1, and 16 in patients 1-3 respectively) ICD shocks delivered. At 12 month follow-up, none of the participants experienced any episodes of ATP or ICD shock. Ejection fraction remained consistent pre-post SBRT.

Conclusion: SBRT showed remarkable success in reducing ATP and ICD shock episodes, facilitating uncomplicated 1 year follow-up in 3 male patients with NICM and VT from the anterolateral papillary muscle.