Non-invasive cardiac radioablation for ventricular Tachycardia

Keywords: Cardiac Radioablation, SABR, Non Invasive, Ventricular Tachycardia Introduction: There is a large body of experience from the field of radiation oncology in delivering Stereotactic ablative radiotherapy (SABR) to extremely small targets with very high accuracy. However, recent evidence suggests that SABR may have an emerging role in the treatment of patients with abnormal heart rhythms, Ventricular Tachycardia (VT), a non-malignant condition with high mortality. (1,2,3,4) Using SABR to treat VT represents a novel treatment alternative for cardiac patients too sick for invasive treatments or in whom conventional therapies, including invasive cardiac catheter ablation, have failed. This is the first completely non-invasive therapy for cardiac arrhythmias and could reduce procedure times for patients from up to 8 hours down to around 45 minutes, without risk of general anaesthesia or invasive ablation procedures. Method and Materials: Non-invasive 3D electro-anatomical mapping and diagnostic CT scanning of the heart were used to define the VT substrate by Cardiology and an ITV developed to incorporate the VT target using RayStation (RaySearch Laboratories AB, Sweden) treatment planning system. Organs at risk were defined including coronary arteries and great vessels. The ITV was then grown to incorporate cardiac and respiratory motion based on a 4D-CT. A VMAT plan was then created, using 3 partial arc 10MV FFF beams, with 25Gy prescribed to 95% of Planning target volume (PTV) in a single fraction. Individual CBCT parameters were developed to optimise image quality in preparation for treatment delivery. Results: Organ at risk doses were kept to within mandatory constraints and a total dose of 25 Gy was delivered in a single 45 minute procedure. Pre, mid and post treatment CBCT’s were acquired and showed that intrafraction motion was within1 - 2mm throughout. Prior to the treatment the patient had incessant VT and ICD shocks. 10 days post treatment it was observed that VT episodes were brief and non-sustained. Conclusion and Discussion: This collaborative approach, has enabled the implementation of non-invasive cardiac radioablation for ventricular tachycardia in our centre. This innovative technique may provide a new treatment option for patients who have exhausted conventional treatments. Numerical References 1. Cuculich, P.S., Schill, M.R., Kashani, R., Mutic, S., Lang, A., Cooper, D., Faddis, M., Gleva, M., Noheria, A., Smith, T.W. and Hallahan, D., 2017. Noninvasive cardiac radiation for ablation of ventricular tachycardia. New England Journal of Medicine, 377(24), pp.2325-2336.2. Robinson, C.G., Samson, P.P., Moore, K.M., Hugo, G.D., Knutson, N., Mutic, S., Goddu, S.M., Lang, A., Cooper, D.H., Faddis, M. and Noheria, A., 2019. Phase I/II trial of electrophysiology-guided noninvasive cardiac radioablation for ventricular tachycardia. Circulation, 139(3), pp.313-321. 3. Sharp, A.J., Mak, R. and Zei, P.C., 2019. Noninvasive Cardiac Radioablation for Ventricular Arrhythmias. Current Cardiovascular Risk Reports, 13(1), 4. Cvek, J., Neuwirth, R., Knybel, L., Molenda, L., Otahal, B., Pindor, J., Murárová, M., Kodaj, M., Fiala, M., Branny, M. and Feltl, D., 2014. Cardiac radiosurgery for malignant ventricular tachycardia. Cureus, 6(7), p.e190. p.1.