1133 - Preservation of Left Ventricular Systolic Function Following 25 Gy Stereotactic Arrhythmia Radioablation

03:50pm - 03:55pm ET

Room 107

Presenter(s)

Raphael William, MD - University of Ottawa, Ottawa, ON

R. William¹, C. J. Redpath², C. Haberl², A. M. Crean³, D. I. Paterson², R. deKemp², P. Nery², M. Golian², S. Hansom², G. G. Cook¹, and D. Tiberi¹; ¹Division of Radiation Oncology, The Ottawa Hospital, Ottawa, ON, Canada, ²Division of Cardiology, The University of Ottawa Heart Institute, Ottawa, ON, Canada, ³Centre for Cardiac Research Manchester, Manchester, Hong Kong

Purpose/Objective(s):

Stereotactic Arrhythmia Radioablation (STAR) delivers targeted radiation (25 Gy) to the myocardium. We analyzed the absolute change in Left Ventricular Ejection Fraction (LVEF) using transthoracic echocardiography (TTE) to characterize safety profile of this therapy and characterize potential non- arrhythmia benefits of STAR.

Materials/Methods:

We conducted a retrospective analysis on a prospectively maintained registry of patients treated with STAR at our institution. Patients with both pre- and post-treatment (3-9 months) TTE LVEF data were categorized into three groups based on absolute change in EF (post-treatment minus pre-treatment): Decreased (loss of = 5 points), Stable (change between -4.9 and +4.9 points), and Increased (gain of = 5 points). Group characteristics and treatment variables, specifically mean heart dose (across the entire contoured volume of the heart), were compared using single-factor ANOVA. Furthermore, the cohort was divided into quintiles based on the mean dose to correlate dose distribution with the incidence of EF change using Chi-square.

Results:

Of the 43 treated patients in the registry, 36 had complete pre- and post-treatment TTE EF data. The distribution across the functional outcome groups was: Decreased EF in 3 patients (8.3%), Stable EF in 21 patients (58.3%), and Increased EF in 12 patients (33.3%). The mean absolute changes in EF for these groups were -7.7, +0.2, and +12.6 points, respectively.

The average mean heart doses delivered for the Decreased, Stable, and Increased groups were 10.2 Gy, 9.7 Gy, and 9.5 Gy, respectively. There was no statistically significant association found between mean heart dose and the defined change in EF (ANOVA p = 0.890). When stratifying patients by mean heart dose quintiles (Q1 being lowest dose, Q5 being highest), the incidence of EF change across groups did not demonstrate a significant correlation (Chi-square p = 0.382). For instance, the lowest dose quintile (Q1) saw 0 Decreased, 5 Stable, and 2 Increased EF outcomes, while the highest dose quintile (Q5) saw 1 Decreased, 5 Stable, and 1 Increased EF outcome.

Conclusion:

In this expanded analysis, 25 Gy single-fraction STAR was not associated with short-term reduction in systolic function. Contrary to concerns regarding radiotoxicity, the majority exhibited either stable or significantly improved LVEF on follow-up TTE (91.6%). Prospective randomized data is needed to more definitively assess the impact of STAR on LVEF.