Author: Karam Ayoub, Aaron B Hesselson, Ronald C McGarry, Joshua Misa, Damodar Pokhrel 👨🔬
Affiliation: University of Kentucky, Department of Radiation Medicine, University of Kentucky, Department of Cardiology 🌍
Purpose: Noninvasive stereotactic body radiosurgery (SBRS) is emerging treatment option for advanced heart failure patients with refractory-ventricular tachycardia (rVT) who experienced recurrent implantable cardiovascular defibrillator (ICD). We report our SBRS treatment-workflow, dosimetry-metrics, and patient reported clinical outcomes.
Methods: Five rVT patients underwent 4D-CT based standard SBRS simulation with/without IV contrast-enhanced CT. Utilizing electroanatomical-mapping with a Medtronic-Vest, target was outlined by an experienced electrophysiologist(s) via AHA 17-segment model. PTV includes target plus 3-5mm isotropic margin:34.5+/-33.5(9.9–93.3)cc. SBRS plans utilized highly non-coplanar/partial-arc VMAT, optimal collimators/couch positions on TrueBeam (6MV-FFF/Acuros-XB) for single-dose of 25Gy (maximum, 31.3Gy). SBRS plans were optimized for target coverage, conformity, and sparing critical organs including heart–PTV. CBCT-based IGRT with 6DOF couch corrections were used. Patients followed up for rVT episodes requiring therapy, including anti-tachycardia pacing/ICD shocks before/after SBRS.
Results: The SBRS plans provided conformity index:1.00+/-0.03(0.99–1.05); steep dose-gradient:2.97+/-0.24(2.66–3.31) and mean heart–PTV dose:2.8+/-0.9(1.7–3.7) Gy. Adjacent OAR maximum dose including stomach/small-bowel were kept low. Patient-specific QA and independent Monte-Carlo second check were 99.1% (2%/2mm criteria) and 1.6%. SBRS was delivered in <20min with 6.8+/-1.7(5.1–9.3)min beam-on time. All patients survived post-SBRS with no adverse effects. Median follow-up interval was 9.9(3.0–19.8)months. First patient had >20 events/month; received SBRS targeting mid-lateral LV wall, reduced VT burden (none). Second, third, and fifth patients had 10-50 events/month before-SBRS, reduced VT burden post-SBRS (0-2 events). Fourth patient didn’t experience rVT but had frequent PVCs, which interfered with biventricular (BiV) pacing: BiV pacing improved from 68 to 89% post-SBRS.
Conclusion: Highly non-coplanar SBRS planning and treatment delivery method with no patient collision concern provided highly-conformal radiosurgical dose distribution for rVT patients while sparing critical organs. SBRS treatment was feasible, safe, and effective at reducing rVT/PVC burden in advanced heart failure patients and improved their quality of life. Longer clinical follow up result of larger rVT SBRT cohort is ongoing.