An in-silico assessment of efficacy of two novel intra-cardiac electrode configurations versus traditional anti-tachycardia pacing therapy for terminating sustained ventricular tachycardia

Figures

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  Fig. 1. (a) Model generation pipeline of porcine LV meshes from in vivo MRI. (b) Placements of novel bipolar electrodes in the LV models, viewed from side and top. ATP delivery sites in all three LV models are marked with green dots which replicate the delivery site in clinical ICDs (apical septum of right ventricle). (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

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  Fig. 2. The ventricular tachycardia cycle lengths (VTCLs) histogram.

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  Fig. 3. Bipolar and transmural electrode configurations and field distributions. Bipolar electrode (left, black) and transmural electrode (right, blue and red) configurations in Model 1 shown in side and top views. The clipping images show the extracellular potential distribution during stimulus delivery. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

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  Fig. 4. Sensitivity tests setup of the transmural electrode configurations shown in direct (left) and side (right) views. First test (top) varies the location of the ground electrode (outside the LV) in 5 different locations. The middle blue electrode represents the same location as the default setup. Second test (centre) shows the prolongation of the transmural electrodes. Third test (bottom) shows the movement of the positive electrode to be outside of the LV cavity, which maintains a shock vector through the CI. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

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  Fig. 5. Transmembrane potential (Vm) maps of at different timings during slow VTs induced in Model 1, 2 and 3, along with a fast VT induced in Model 2. VTCLs are 400 ms, 350 ms, 530 ms and 270 ms. Only the first time plots show the scar region while the others are removed in order to clearly show the pathway of activation wave. The black arrows show the propagation direction of the VT through the CI. The black circles mark the small extra pathways at the exit of the CI in Model 1 and 2.

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  Fig. 6. Average minimum stimulus strength needed, for terminating VT with the bipolar (left blue line) and transmural (right red line) electrode configurations, is plotted against the shock delivery time defined as the percentage of the VTCL since the last activation detected at the CI. Note that at 50% and 60% of VTCL, some VTs failed to terminate with the maximum delivered stimulus. In these cases, the average value is calculated by eliminating those unsuccessful cases. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

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  Fig. 7. Transmembrane potential (Vm) distributions during shock application with the bipolar electrode configuration showing successful (panel a) and unsuccessful (panel b) VT termination using strength SfEff and strength SpEff, respectively in Model 1. Note that the stimulus applied by the bipolar electrodes starts at 88% VTCL in the CI location, as shown in Fig. 3 and lasts for 5 ms. Two views are shown from the epicardium and the endocardium of the LV. Enlarged views of the CI region are marked by blacked rectangles.

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  Fig. 8. Transmembrane potential (Vm) distributions during shock application with the transmural electrode configuration showing successful (panel a) and unsuccessful (panel b) VT termination using strength SfEff and strength SpEff, respectively in Model 1. Note that the stimulus applied by the tranmural electrodes starts at 88% VTCL in the CI location, as shown in Fig. 3 and lasts for 5 ms. Two views are shown from the epicardium and the endocardium of the LV. Enlarged views of the CI region are marked by blacked rectangles.

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  Fig. 9. (a) Comparison of the efficacy of the bipolar and transmural electrode configurations with ATP, applied to all 40 VT episodes. Strengths SpEff and SfEff for bipolar configuration are 860 V and 1700 V. Strengths SpEff and SfEff for transmural configuration are 80 V and 120 V. (b) Comparison of the efficacies of bipolar and transmural electrodes using strength SfEff with ATP, on slow and fast VTs separately.

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  Fig. 10. Sensitivity analysis of the specific placements and geometry of the transmural electrode configuration, tested on a smaller cohort of 3 VT episodes (one from each LV model). Test 1 varies the placement of the ground electrode outside of the LV to five locations around the CI (5 cases). Test 2 prolongs the electrodes size (3 cases). Test 3 moves the positive electrode outside of the LV cavity, whilst maintaining the shock vector through the CI (3 cases). All stimulus strengths used here are SfEff.