Objectives:

There is a rising interest in using radiosurgery to modify arrhythmogenic substrate in patients with recurrent ventricular tachycardia (VT). However, data on safety are still inadequate. This is an update of toxicity evaluation based on the compilation from our case series, NIRA-VT (NCT03601832) and STAR-VT (NCT04612140).

Methods:

Between 2014 and June 2022, 39 patients (36 males, 3 females; mean age 66 ± 10 years) with structural heart disease (ischemic cardiopathy, dilated cardiopathy or fibroma-associated scar) from two electrophysiology centers in the Czech Republic (Trinec, Prague) underwent radiosurgery for recurrent VT. Radiosurgery was performed after at least one failed catheter ablation for VT. The critical part of the VT substrate was identified by electroanatomic mapping using a combination of voltage mapping, pace mapping, and activation mapping; and it was marked on a contrast-enhanced computer tomography study as a CTV. In the NIRA-VT trial, CTV included scars based on PET/CT evaluation. A radiosurgery system with real-time motion tracking using the tip of the ICD lead of an indwelling defibrillator as a fiducial marker was used. A total radiation dose of 25 Gy was delivered to the ablation target in a single session during free breathing. Radiation-induced toxicity was evaluated according to the Common Terminology Criteria for Adverse Events (CTCAE) version 4.0. Only patients with follow-up longer than 6 months were included in the long-term radiation-related side effects evaluation.

Results:

The mean CTV and PTV were 28 (range 6-53) ml and 13 ± 91 ml respectively. No patient exhibited acute (up to 3 months) elevation of troponin, pericardial effusion, or a decrease in left ventricular ejection fraction from baseline. Four patients developed acute mild nausea, which waned after antiemetic drugs. Long-term radiation-related side effects were evaluated in 30 patients. Four patients (13 %) presented radiological signs of lung fibrosis in a small area at a close distance from PTV. Except for two patients (7 %) with grade 1, there was no significant decrease in left ventricular ejection fraction during follow-up. Eight patients (27 %) gradually developed significant progression of known valve regurgitation after SBRT, three (10 %) of them had to undergo mitral valve replacement (grade 4 toxicity) and one tricuspidal regurgitation (grade 3) probably unrelated to SBRT was detected. Two cases of esophagitis (10 %) were seen with one radiation toxicity-related death (grade 5 toxicity) due to the unresectable esophagi-pericardial fistula (5 %).

Conclusion(s):

Our data indicate the feasibility of radiosurgery, the majority of patients presented no/mild radiation-related toxicity and a decrease in VT burden. However, we have seen three cases of severe toxicity including one death. To further investigate the long-term safety and efficacy of radiosurgery for VT, enrolling in a randomized prospective study (NCT04612140) is in progress.