Characteristics of recurrent ventricular tachycardias after stereotactic body radiotherapy

Abstract

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Grant project AZV NU20-02-00244 from the Ministry of Health of the Czech Republic and European Union's Horizon 2020 research and innovation program under grant agreement No 945119. Introduction Stereotactic body radiotherapy (SBRT) is a novel treatment for otherwise resistant ventricular tachycardias (VTs). Different mechanisms of SBRT for VT suppression were proposed that include radiation-induced fibrosis but also SBRT-triggered increase in myocardial conduction velocities without significant fibrotic changes. Purpose The study compared the morphologies and cycle lengths (CLs) of inducible VTs during re-do catheter ablation after SBRT with VTs before SBRT. Methods We investigated patients that underwent SBRT (a single session of 25 Gy) for refractory VT and subsequent electrophysiology study / reablation for recurrences of VTs. All inducible VTs were analysed concerning morphology and CL. Results A total of 9 patients (2 women, aged 60 ± 13 years) were included. Two patients had ischemic heart disease, six patients had nonischemic cardiomyopathy, and one had a cardiac fibroma. All patients were on chronic amiodarone treatment. The mean ejection fraction of the left ventricle was 35 ± 12%. The mean planning target volume for SBRT was 39 ± 21 ml. Electrophysiology study/reablation was performed at a mean interval of 8 months (interquartile range: 2-10months) after SBRT. A total of 23 and 27 distinct VT morphologies were inducible before and after SBRT, respectively. Twelve pairs of VTs (44%) were identified that had identical morphology before and after SBRT. The mean CL of these VT pairs decreased from 399 ± 98 ms to 472 ± 74 ms (P = 0.01) after SBRT. Overall, 15/27 of all VT morphologies induced after SBRT originated from the irradiated region. Conclusions Recurrent VTs after SBRT had commonly origin in the irradiated region. In pairwise comparison, the CL of VTs has prolonged after the SBRT. This suggests that SBRT results in radiation-induced fibrosis rather than an increase in conduction velocity.