Stereotactic Cardiac Ablative Radiotherapy (SCAR) for Refractory Ventricular Tachycardia: Western Australia Experience

Abstract

Ventricular tachycardia is a potentially life-threatening cardiac condition that is associated with significant morbidity and mortality. Despite advances in medical therapies, implantable cardioverter-defibrillator (ICD) and catheter ablative therapy (CAT), some patients continue to suffer recurrent VT. SCAR is a highly accurate, non-invasive, and novel ablative therapeutic option that has shown promising results in the treatment of refractory VT patients associated with structural heart disease. Early case series and subsequent prospective clinical trials have demonstrated SCAR to be well-tolerated with acceptable safety profiles and consistently decreased VT episodes in VT patients, who failed all conventional antiarrhythmic medications and CAT. The aim of the current study is to report the efficacy and safety/tolerability of SCAR in ICD-dependent patients with refractory VT in Western Australia, Australia. Seven patients with recurrent refractory VT, deemed high risk or non-suitable for CAT, were referred to GenesisCare at Fiona Stanley Hospital, Western Australia for SCAR between July 2020 and November 2022. Target volume definition and delineation involved interdisciplinary teams by combining all available clinical, electrophysiological mapping and diagnostic/planning cardiac imaging data to generate radiotherapy plans. Patients were treated whilst awake, with a single dose of 25 Gy using VMAT technique on the Synergy Linac with stereotactic X-ray tool capability. Efficacy was assessed by counting the number of episodes of VT and ICD shocks after SCAR. Safety and tolerability were evaluated by treatment related toxicities during follow up. Of the seven patients referred for SCAR, only five received SCAR as two patients died from their refractory VT before their radiotherapy. For the patients receiving SCAR with at least 6 months follow-up, overall reduction in VT episodes and ICD shocks was 95% and 85%, respectively. No significant treatment-related toxicities were documented during follow-up. Two patients had died. Neither of their deaths were directly attributed to their radiotherapy. One patient died after requesting to cease her antiarrhythmic medications and to have her ICD switched off 2 days after SCAR (against medical advice). The other patient died 431 days after SCAR from aspiration pneumonia after fracturing her cervical spine following a fall at home and was unrelated to her VT. Our data reflects international experience in terms of treatment efficacy and safety profiles of SCAR for patients with refractory VT. SCAR is increasingly recognized as an alternative cardiac ablative option for ICD-dependent VT patients who failed all conventional antiarrhythmic treatments. Nonetheless, careful patient selection and longer-term follow-up are required to ensure the optimal treatment outcomes can be achieved in these patients.