Experimental His-Bundle Pacing: Histopathological and Electrophysiological Examination

His-bundle pacing gives a more physiological ventricular contraction in comparison to right ventricular apical pacing. However the problems of lead fixation and stability of long-term His-bundle pacing are yet unsolved. We used six adult beagles, in which a screw-in lead was anchored in the His-bundle region for observation of the pacing conditions and histopathologic changes of the conduction system over the course of 2 months. In the results, a satisfactory fixation was obtained using a conventional screw-in lead and no histological influence on the conduction system was observed. The pacing threshold at the time of implantation was 1.15 ± 0.69V (3.23 ± 3.08 mA) in the pulse width of 0.5 ms. R wave amplitude, the impedance and slew rate were 7.28 ± 2.04 mV, 409 ± 102 Ohm, and 0.65 ± 0.41 V/s, respectively. Two months later, these parameters changed to 2.83 ± 1.06 V (10.4 ± 5.71 mA), 5.63 ± 1.62 mV, 310 ± 71.3 Ohm, and 0.49 ± 0.22 V/s, respectively. These results suggest the feasibility of clinical application of permanent His-bundle pacing.