Session Item

Noninvasive cardiac radioablation has been reported to be effective and relatively safe for ventricular tachycardia (VT) in preclinical and clinical studies. However, previous studies implementing cardiac radioablation set a 6-12 week “blanking period” and focused on long-term effects rather than reporting the early changes. In this prospective trial, we focused on the early antiarrhythmic effects within one month after cardiac radioablation. In particular, we aimed to determine the differences in response according to the cause of VT.

From September 2019 to December 2020, 6 patients (3 ischemic VTs and 3 non-ischemic VTs) were included in this trial and treated with cardiac radioablation with a single fraction of 25 Gy for intractable VT or premature ventricular contraction-induced cardiomyopathy. Imaging studies, 12-lead ECG, and electrophysiological mapping were used to localize the treatment target. The internal target volume was delineated considering the respiratory motion. To measure the early response after cardiac radioablation, 24-hour Holter monitoring was performed from 24 hours before the treatment to 48 hours after the treatment. Additionally, all patients had Holter monitoring one month before and after the cardiac radioablation. 

The median follow-up time was 9.6 months. The number of total ventricular beats decreased by 58% and 60% within 24 hours and 48 hours after cardiac radioablation, respectively. It further decreased to 30% of the pre-treatment number of total ventricular beats at one month after cardiac radioablation. On further analysis of the ventricular beats, VT decreased earlier and more dramatically than that of premature ventricular contractions (PVCs). Additionally, the duration of the longest VT run was shortened after cardiac radioablation, suggesting that disintegration of VTs into shorter VTs and PVCs was the main cause of early anti-arrhythmic effects. Notably, VT burden decreased more markedly in the patients with ischemic cardiomyopathy compared to the non-ischemic cardiomyopathy patients after cardiac radioablation. All patients were alive and there was no severe acute toxicity during the follow-up period.

In patients with intractable VT, noninvasive cardiac radioablation with a dose of 25 Gy resulted in an immediate decrease of ventricular beats before the period when tissue fibrosis is expected to occur. The decrease of VT burden through the shortening of VTs already began within 24 hours after the procedure and continued to decrease until one month after the radioablation. The treatment effect was more remarkable in ischemic VT patients compared to non-ischemic VT patients in this cohort and should be validated in larger studies.