NON-INVASIVE CARDIAC RADIOABLATION FOR RECURRENT VENTRICULAR TACHYCARDIA: INITIAL RESULTS AND INSIGHTS

BACKGROUND Non invasive cardiac radio-ablation (RA) has emerged as an alternative to escalating anti arrhythmic drugs (AADs) in patients who are unwilling or unable to undergo catheter ablation (CA) for recurrent ventricular tachycardia (VT). We present our initial experience of treating 9 patients on a compassionate use basis and offer insights into programme development and delivery in Canada. METHODS AND RESULTS Twenty four patients have been referred to the programme since August 2019. We have treated 9 patients with RA as 12 patients declined and another three underwent emergent CA for VT storm. Of the 15 patients who did not receive RA, 10 are now deceased (67%). Following RA one patient (11%) deceased at 11 months due to respiratory infection. Although highly selective, clinical characteristics between those receiving and not receiving RA are similar. Patients undergoing RA are medically stabilised and receive echo, CT and PET scanning similar to patients undergoing CA. All 9 patients underwent non invasive EP study (NIPS) under light sedation administered by a single IV cannula without complication. VT is induced using the ICD in situ and mapped using the CardioInsight ECGi system. Targets for RA are identified combining the ECGi data with the contemporaneous imaging data. This analogue process involves Cardiac EP/ Imaging, Radiation Oncologists and Medical Physicists. The median time to RA from NIPS is 12 working days (IQR 8, 20). A single fraction of 25 Gy is targeted using 4D-CT with an average on beam time of 15 minutes. All patients receive Rivaroxaban 20 mg for thirty days post RA. Thus far 1 patient (11%) has suffered pneumonitis requiring a 4 week course of oral corticosteroids, but there have been no other adverse events attributable to RA. Post RA 8 patients (89%) experienced an immediate reduction in VT burden as recorded by their ICD. As compared to the 6 months prior to RA, there was a greater than 90% reduction in VT requiring ICD therapy (ATP or shocks) and at 9 months only 1 patient (11%) has suffered recurrent ICD shocks. The majority of patients (67%) have had antiarrhythmic drug therapy reduced or withdrawn post RA. CONCLUSION Non invasive cardiac radioablation appears safe, well tolerated and effective in the short term for those unwilling or unable to receive catheter ablation for recurrent VT. Several opportunities remain to improve logistics, targeting and availability of the procedure to improve outcomes for this cohort of patients in Canada.