Provocative Cases -> Teaching Case Reports D-PO01 - Featured Poster Session (ID 11) Poster

D-PO01-094 - The Mechanism Of Recurrent Ventricular Tachycardia After Stereotactic Radioablation: Two Instructive Cases (ID 86)


Background: Stereotactic body radioablation (SBRT) is emerging as a treatment for ventricular tachycardia (VT) refractory to catheter ablation. However, 3/34 patients in published trials had no VT burden reduction.
Objective: we report two patients restudied at catheter ablation due to VT recurrence following SBRT
Results: Both patients had ischemic cardiomyopathy, large anteroapical scar, severe systolic LV dysfunction, VT refractory to antiarrhythmics and catheter ablation, and received SBRT at 25Gy. Patient 1 had recurrent VT with apicolateral exit that responded to SBRT but developed a new VT on antiarrhythmic medication taper 4 months later. This VT had a periaortic exit using a critical isthmus within patchy scar bordering the prior SBRT treatment zone, which was densely scarred. The basal septal region had been intentionally spared due to ICD lead tip position and proximity to the conduction system, valves and coronary arteries (Panel A). Patient 2 experienced recurrence at 4 weeks post radioablation with incessant VT identical to his prior clinical VT, despite 95.8% of the target volume receiving >95% of prescribed dose. There was slow conduction through the anteroseptal aneurysm between islands of calcification, with a far field mid diastolic potentials (white arrows) that could not be pace-captured by intramural needle catheter (Panel B).
Conclusion: Catheter ablation following SBRT is feasible and was without complication. 25Gy dose for ischaemic scar may be inadequate in some patients. Arrhythmia recurrence at treatment border-zones is possible, highlighting the importance of accurate translation of the electroanatomical target to treatment volume.