A case report of successful elimination of recurrent ventricular tachycardia by repeated stereotactic radiotherapy: the importance of accurate target volume delineation

Figure 1. Panel (A) shows 12-lead electrocardiogram of clinical VT. Panel (B) depicts an activation map (CARTO3, Biosense-Webster) of the left ventricle during VT in the modified left lateral view. Activation times are colour coded with the red corresponding to the earliest. Panel (C) shows local intracardiac electrogram at the site of the earliest endocardial activity during VT (see text for details).

Figure 2. Electroanatomical bipolar and unipolar voltage maps depicting left ventricle in the left lateral view obtained during the first ablation procedure (A, B), before the first SBRT (C, D), and prior the second SBRT (E, F). Voltage is colour-coded, cut-off values for scar detection were set to 1.5 mV and 8.3 mV for bipolar and unipolar voltage, respectively. Note the absence of a new detectable scarring after the first ablation session despite numerous radiofrequency applications. Interestingly, the earliest endocardial activity during VT (white circle) overlapped with the area of low unipolar voltage, while it was only neighbouring the low bipolar voltage region. This indicates that the maximum scarring after the first SBRT occurred only adjacent to the desired target. MA, mitral annulus.

Figure 3. Overview of PTV selection for the second SBRT using the image integration (see text for details). Panel (A) shows a 3D model of the LV and LA imported from the electroanatomical mapping system in dedicated software (slicer.org). Panels (B) and (C) depict endocardial contours of the LA and LV projected onto the raw CT images confirming proper registration. The PTV is projected on the CT slice by yellow colour (arrow). 3D, three dimensional; CT, computed tomography; LA, left atrium; LV, left ventricle; LPV, left-sided pulmonary veins; PTV, planned target volume; RPV, right-sided veins.