Purkinje Fibers in Canine False Tendons: New Anatomical and Electrophysiological Findings

Figure 1. The distribution of Purkinje fibers in the left ventricular endocardium. (a, d) There was no Purkinje fiber branch found within 0.5 cm below the mitral valve; (b, e) showed there was no Purkinje fiber branch found within 0.8 cm below the aortic valve; (c, f) there was no Purkinje fiber branch found on the tip of the papillary muscles. MVL, mitral valve leaflet; LCC, left coronary cusp; RCC, right coronary cusp.

Figure 2. The distribution characteristics of Purkinje fibers on chordae tendineae (true tendons) and FTs. (a) Lugol's liquid staining in a dog's endocardium: Purkinje fibers were dyed darker. (b, c, and d) No Purkinje fibers contained in chordae tendineae which connected to the mitral valve. (b) The enlarged triangular region of (a). (c) Masson's staining of chordae tendineae (×100). (d) Connexin 40 immunohistochemical staining of chordae tendineae (×100). (e, f, g, and h) All of the FTs contain Purkinje fibers. (e) The enlarged star region of (a) (×5). (f) The enlarged rectangular area region of (e) (g) Masson's staining of FTs (×100). (h) Connexin 40 immunohistochemical staining of FTs (×100).

Figure 3. Purkinje fibers, typical working myocardium, and vasa vasorum in the larger FTs (×50). (a) HE staining; (b) Masson's staining; (c) PAS staining; (d) connexin 40 immunohistochemical staining. M, working myocardium; P, Purkinje fibers; black arrow, vasa vasorum.

Figure 4. Electrophysiologic mapping of the endocardium using the DVM method. (a) Two 20-electrode mapping catheters were positioned at the LV septal endocardium from the upper septum to the apex. One mapping catheter (P1–P20) was stuck on one of the FTs, and the other one (P21–P40) was placed at the adjacent Purkinje network. Pacing point is located at the proximal end of FT (red star). (b) Lugol's liquid staining in the dog's endocardium: Purkinje fibers were dyed darker. (c) When pacing from the proximal FTs, at the cycle length of 400 ms, the conduction direction of Purkinje fibers contained in the FT was from the proximal to the distal end, and the conduction direction of Purkinje fibers on the apical endocardium was from the distal to the proximal end. After stopping the pacing, Purkinje fiber automaticity from FTs (the four to eight beats) was observed. (d) When pacing at a cycle length of 250 ms, decremental conduction of Purkinje fibers occurred, and the activation sequences of Purkinje fibers were the same as that of 400 ms pacing (c).

Figure 5. Multiple potentials were recorded in the overlapping area of FTs. (a) A 20-eletrode mapping catheter was positioned at the overlapping area of FTs; (b) multiple rows of Purkinje potentials were recorded.

Figure 6. The schematics of our hypothesis about the possible reentrant circuits of idiopathic left fascicular ventricular tachycardia. (a) The anatomical structure and conduction pattern of the Purkinje network during sinus rhythm. During sinus rhythm, the main branch of His-Purkinje system (the apical hierarchy) exhibited antegrade activation sequence (P2, red lines and arrows) and then retrogradely activated the Purkinje network on the basal hierarchy (P1, blue lines and arrows). The green line and arrows represented the tiny FT between the Purkinje network on the same basal hierarchy or different hierarchies. (b) During VT, the reentrant circuit was around the Purkinje fiber network, which might be connected by the tiny FT as a slow conduction zone (red lines and arrows). To note, the left posterior fascicle (P2) was a bystander of the reentrant circuit. (c) During VT in rare cases, the slow conduction zone was from a longer FT connecting the Purkinje network and the papillary muscles (red lines and arrows). (d) The possible anatomical basis of idiopathic left fascicular VT in (b) (e) The possible anatomical basis of idiopathic left fascicular VT in (c) LPF, left posterior fascicle;…