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).