P5690Comparison of two methods to navigate the stereotactic body radiotherapy ablation for ventricular tachycardia, the invasive electrophysiological study and substrate identification

Abstract

Abstract Purpose To compare two methods used for identifying the arrhythmogenic substrate - invasive electrophysiological study versus PET-CT scar identification. The substrate is then targeted by stereotactic body radiotherapy (SBRT) in patients with previously unsuccessful radiofrequency catheter ablation. Methodology Patients with ischemic cardiomyopathy, LVEF less than 40% and unsuccessful conventional treatment resulting in recurring ventricular tachycardias, were divided into two groups with different methods of obtaining arrhythmogenic substrate. In the group A, invasive electrophysiological mapping was used, while in the group B, scar identification by PET-CT was done, enhanced with non-invasive body surface ecg mapping of all inducible ventricular tachycardias. This target obtained was then attacked with SBRT. We compared the size of the planned target volume (PVT), the SBRT duration, the calculated dose for the esophagus, stomach and lung and the incidence of acute complications. Cohort description Patients in group A were recruited from April 2014 to December 2018, patients in group B from June to December 2018. Group A (8 patients) – mean age 66, NYHA class 2.4, LVEF 29,4%. Group B (6 patients) – mean age 71, NYHA class 2.1, LVEF 25,2%. All patients were men. Results There was a statistically significant difference in PTV – Group A (mean 24.1ml, SD = 3,9), Group B (mean 76.0ml, SD 14.1), p<0,001 (two-sample t-test). There was no difference in the calculated secondary radiation doses acquired by surrounding organs. The most frequent adverse event was acute anorexia, occurring in 4 patients from Group A and in 2 patients from Group B. The anorexia subsided in one week time. One patient from Group B suffered from esophageal ulcer, which developed 6 months after the therapy. Conclusion Using invasive electrophysiology mapping to identify arrhythmogenic substrate for SBRT yields significantly smaller volume of targeted tissue. Despite this finding, we did not find any difference neither in radiation dose delivered to the surrounding organs, nor in the radiation duration.