Computational ECG mapping and respiratory gating to optimize stereotactic ablative radiotherapy workflow for refractory ventricular tachycardia

Figures

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  Figure 1. Reduction in implantable cardioverter-defibrillator (ICD) shocks following radioablation. ICD shocks were significantly decreased from 23 ± 12 shocks in the 6 months prior to stereotactic ablative radiotherapy (36 patient-months) to 0.67 ± 1.0 shocks at 6.0 ± 4.9 months follow-up (P < .005).

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  Figure 2. Respiratory-gated delivery of radiation. Example of patient 2, in whom respiratory-gated delivery was performed (see Supplemental Video 1). Fluoroscopy shows displacement of the implantable cardioverter-defibrillator (ICD) lead up to 2.2 cm during the respiratory cycle. The beam is turned on during expiration and off during inspiration, with the respiratory cycle tracked by an external optical tracking system. A, B: Proper timing of therapy is verified using intermittent fluoroscopy to confirm that the ICD lead is within the green contour during expiration (A) when beam is on and that the beam is off when the ICD lead is outside of the green contour during inspiration (B). C: On the gated expiratory phase 4-dimensional computed tomography study (4DCT), the inferior wall and ICD lead are clearly separated from the stomach (0.8 cm distance, yellow marker). D: On the nongated 4DCT, the inferior wall VT target (red planned treatment volume contour) and ICD lead are shown overlying the contrast-enhanced stomach (yellow marker).

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  Figure 3. Noninvasive 12-lead electrocardiogram computational mapping. Example arrhythmia source mapping results and their corresponding cardiac segment are shown for this population with refractory ventricular tachycardia.

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  Figure 4. Histologic effects of stereotactic ablative radiotherapy for patient 1. A: Dense fibrosis at the basal anteroseptum. B: “Wavy fibers” mixed with fibrosis on trichrome stain of the basal anterior mitral annulus within the targeted region. C: No obstruction seen in the left circumflex coronary artery that was located in the targeted region. D: Preserved myocardial structure outside targeted areas.

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  Figure 5. Close proximity of the inferior wall to the stomach. Computed tomography images from all patients showing the close proximity of the stomach to the basal inferior left ventricle wall (4.8 ± 1.0 mm) for each study patient. The smallest distance was 3.7 mm in patient 6.