Background:
Stereotactic ablative radiotherapy (SAbR) is an emerging therapy for ventricular tachycardia (VT) storm, but the feasibility and outcomes guided by computational 12-lead ECG mapping and respiratory-gated radiation delivery have not been reported.
Hypothesis:
We hypothesized that a novel 12-lead ECG-based mapping system and respiratory-gated radiotherapy delivery may simplify the workflow and improve precision of SAbR in critically ill patients with VT storm.
Methods:
We enrolled patients with VT storm who were not candidates for catheter ablation. VT was induced using non-invasive stimulation and recorded on 12-lead ECGs. Computational ECG mapping was performed to localize VT exit sites. Target volumes were contoured onto an averaged free-breathing CT. Ionizing radiation (25 Gy) was delivered using a linear accelerator (Varian, Palo Alto). In patients with significant respiratory motion, radiotherapy was delivered at end-expiration, guided by ICD lead fiducials.
Results:
In 5 patients (age 74±6.1 years, EF 29±14%) refractory to 2±1 ablation procedures, 1.5±0.6 VT morphologies were localized on 3D models (Fig 1A) using ECG-based mapping (mapping time 1.2±0.3 min). In patients whom respiratory gating (Fig 1B) was used prospectively due to respiratory variation, the planned target volume (PTV) was smaller compared to patients who were not gated (71 ± 7 vs 153 ± 35 cc, p<0.01). These patients also had VT targets (crux or inferior LV) close to the stomach, and did not experience adverse events. ICD shocks were decreased after SAbR compared to before (0.25±0.5 vs 26±19 shocks, p<0.001) at 4.4±3.4 months follow-up.
Conclusion:
Non-invasive computational mapping based upon the 12-lead ECG alone simplifies radioablation workflow in critically ill VT storm patients and reduces the burden of ICD shocks. Respiratory gated radiotherapy ablation appears feasible and may help reduce target volume of therapy. Studies with longer follow-up are ongoing.
NOVEL MAPPING AND TARGETING TECHNOLOGIES IMPROVE THE EFFICIENCY, PRECISION AND SAFETY OF STEREOTACTIC ABLATIVE RADIOTHERAPY FOR REFRACTORY VENTRICULAR TACHYCARDIA
