PMC9669661_01
Twelve-lead electrocardiography of the patient. (A) VT with right bundle branch block morphology and an inferior axis. (B) VT with right bundle branch block morphology and a superior axis. (C) VT with the origin in the RVOT. (D) Slow VT with all positive concordance in the precordial leads and an inferior axis suggested at a different location from the initial therapy zone. (E) The morphology of ventricular premature beats was the same as the morphology of the slow VT.
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F1
The twelve-lead electrocardiogram revealed two different morphologies of clinical VT (Figures 1A,B).
Bipolar voltage mapping with a 3D CARTO mapping system (Biosense, Diamond Bar, CA). (A) The presence of a large, uneven, mixed scar and viable zone in the area of the left ventricular basal to the middle posteroseptal wall from the right anterior oblique (RAO) view. The arrow indicates LAVA, the substrate, as the target ablation zone. (B) After SBRT, the therapy zone became a scar zone. The arrow indicates local voltage < 0.5 mV. (C) Inferior view of the left ventricle (LV) before SARS. (D) Inferior view of the left ventricle (LV) after SBRT. (E) Cardiac MRI using a wide-band sequence before SBRT. A delay in the enhancement of the mid-basal septal wall and mid-inferior wall was noted, which indicated scar formation in this area. (F) Cardiac MRI after SBRT. The previously shown delay in enhancement of the mid-basal septal wall and mid inferior wall was still present; however, the affected area was slightly larger than that on the previous MRI.
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F2
During the electrophysiology study, bipolar voltage mapping with a three-dimensional (3D) CARTO mapping system (Biosense, Diamond Bar, CA) suggested the presence of a large, uneven, mixed scar and viable zone in the area of the left ventricular basal to middle posteroseptal wall (Figures 2A,C,E).
Multimodal imaging combined with scar imaging, including the CARTO mapping system (Biosense, Diamond Bar, CA), CT, MRI and 99mTc-sestamibi MPI, was used offline to delineate a target for ablation. A plan was developed in the Pinnacle3 planning system (version 9.8.1, Philips Medical Systems, Madison, WI, USA). One day before treatment, quality assurance was performed. On the day of treatment, the patient was immobilized on the vacuum device, and cone-beam computed tomography (CBCT) was used for patient setup and target localization. The treatment unit was aligned with the patient, and a dose of 12 Gy was delivered precisely by volumetric-modulated arc therapy (VMAT) through a linear accelerator machine (Versa HDTM, Elekta, Crawley, West Sussex, UK) with 6 MV photons.
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F3
The procedural workflow is shown in Figure 3.
The substrate was targeted at the clinical target volume (CTV). An internal target volume (ITV) was created from the phased-binned 4D CT images to account for the maximum range of motion that was assessed by reviewing the playback of all the phases of the 4D-CT overlaid with the reference CT scan. The planning target volume (PTV) was generated as a 3-mm volumetric expansion from the ITV. The goal was for at least >= 95% of the PTV to be covered by at least 95% of the prescribed dose (12 Gy). Optimization was performed to place prescription hotspots (areas receiving > 100% of the prescribed dose) within the ITV and CTV, enabling the ITV and CTV to be covered by up to 125% and 150% of the prescribed dose, respectively. (A) Dose volume histogram (DVH) for the PTV and organs at risk. (B) DVH for the PTV and heart substructures. RV, right ventricle; LV, left ventricle; RA, right atrium; LA, left atrium; AO, aorta; ICD, cardioverter-defibrillator. (C) Coronal view of the plan with color wash. (D) Transverse view of the plan with color wash. (E) Sagittal view of the plan with color wash.
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F4
Optimization was used to place prescription hotspots (areas receiving > 100% of the prescription dose) within the ITV and CTV, enabling the ITV and CTV to be covered by up to 125 and 150% of the prescribed dose, respectively (Figure 4).