Mini Electrodes on Ablation Catheters: Valuable Addition or Redundant Information?—Insights from a Computational Study

Figures

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  Figure 1. Exemplary simulation setup for parallel catheter orientation P with an 8 mm nonirrigated ablation catheter. Ablation catheter and myocardium are completely surrounded by blood. ME2 is in direct contact with the myocardium. In this simulation scenario, the ablation catheter is slightly touching the cardiac tissue. The border zone of ablation lesion is shown by a color gradient. The varying resolution of the tetrahedral grid elements with edge lengths from 0.05 to 0.3 mm can be seen.

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  Figure 2. Positioning of ablation catheter and orientation of MEs for orthogonal (a) and parallel (b) orientation. (a) ME1 is oriented towards the reader, perpendicular to the propagation direction of the excitation wavefront. ME2 and ME3 are shifted by an angle of 120°, pointing away and towards the excitation wave, respectively. (b) In parallel orientation, the ablation catheter is tilted and placed flat onto the tissue patch. The myocardium and the catheter are completely surrounded by blood (not shown here). The excitation wavefront is propagating from the left tissue boundary (extracellular potentials are exemplarily shown here, depicting a moment before the excitation has passed the catheter).

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  Figure 3. Movement of the ablation catheter over a point-shaped ablation lesion without border zone in orthogonal (a) and parallel (b) orientation (step size: 0.5–1 mm). Four different positions of the catheter are shown exemplarily. Arrows indicate the direction of movement to before and behind the lesion from the initial position (dotted line). Myocardium is more transparently shown in the direction of movement of the catheter.

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  Figure 4. Movement of the ablation catheter along a linear lesion with a conduction gap in orthogonal (a) and parallel (b) orientation (step size: 0.5 mm). Four different positions of the catheter are shown exemplarily. Arrows indicate the direction of movement from the initial position (dotted line). Myocardium is more transparently shown in front of the linear lesion.

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  Figure 5. Comparison of filtered simulated IEGMs above healthy myocardium and above an acute point-shaped ablation lesion for orthogonal (a) and parallel (b) catheter orientation. Distal: UEGM of distal ablation electrode; ME1: UEGM of ME1; ME2: UEGM of ME2; ME3: UEGM of ME3; ME1-ME2: BEGM of ME1 and ME2; Distal-ME1: BEGM of distal ablation electrode and ME1; and Distal-ME2: BEGM of distal ablation electrode and ME2.

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  Figure 6. Relative changes of unipolar Vpp of the distal electrode, ME1, ME2, and ME3 by varying catheter's tilting angle with respect to myocardium. Vpp were referenced to simulated Vpp at orthogonal orientation of the catheter (90° tilting angle). Relative changes of Vpp for ME1 and ME3 were completely overlapping in all tilting angles.

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  Figure 7. Relative changes of Vpp during rotation for distal electrode (orthogonal orientation and parallel orientation), ME2 (orthogonal orientation and parallel orientation), ME1, and ME3 in parallel orientation. The catheter is rotated above healthy myocardium. All Vpp were referenced to minimum Vpp of each electrode for complete rotation. At an angle around 30°, ME2 is in direct contact with the myocardium. Relative changes of Vpp for distal electrode are completely overlapping in both catheter positions.

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  Figure 8. Comparison of relative changes of unipolar Vpp of the distal ablation electrode and ME2 for changing the penetration depth of the parallel placed catheter in healthy myocardium. In orthogonal orientation, relative changes of Vpp from distal electrode and ME2 were not significant.

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  Figure 9. Changes of unipolar Vpp of the distal electrode (orthogonal orientation and parallel orientation) and ME2 (orthogonal orientation and parallel orientation) when the catheter was moved above the point-shaped ablation lesion. Vpp were referenced to simulated Vpp at the central position of the catheter (0 mm shift). Negative sign represents a shift towards the propagating excitation wavefront and positive sign represents a shift in the opposite direction.

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  Figure 10. Unipolar EGMs from the distal electrode and ME1 when the catheter is orthogonally moved to the front of the point-shaped ablation lesion (a) and behind the lesion (b). Distance of catheter from center of ablation lesion is illustrated in the figure (from 7 mm to 0 mm).

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  Figure 11. Unipolar EGMs from the distal ablation electrode and ME2 when the catheter is perpendicularly moved to the front of the point-shaped ablation lesion (a) and behind the lesion (b). Distance of catheter from center of ablation lesion is illustrated in the figure (from 7 mm to 0 mm).

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  Figure 12. Relative changes of Vpp from the distal electrode (orthogonal orientation and parallel orientation) and ME2 (orthogonal orientation and parallel orientation) when the catheter was moved above the linear lesion. Vpp was referenced to Vpp at the conduction gap within the linear lesion (0 mm shift).