Figure 6. Subthreshold DAD-like activity in ventricular cells of the Purkinje–myocardial junction cause retrograde excitation of PFs.

(A) Representation of the tissue block (left) used in the computational model. Recording electrode is illustrated for the ventricular (gray) and Purkinje (blue) tissue subtypes. The membrane voltage recording (at right) shows a ventricular DAD (gray) triggering an AP in the PF (blue). (B) Reciprocal experiment demonstrating that Purkinje DADs fail to generate ventricular APs. (C) Schematic representation of the computational model. Clipping plain and zoomed-in inset show the boundaries of the hemispherical juxta-cell region with characteristic r_Juxta. Membrane voltage traces (right), showing DAD-like activity in ventricular tissue (gray; identical regardless of r_Juxta value) and the response in a coupled PF for various r_Juxta values. Evolution of membrane voltage over time in this model for all r_Juxta values can be found in Supplemental Video 1.