Experimental dog models demonstrate that inability to record His potentials may not be due to technical failure, and that specific conduction blocks and 'splitting of H' can be experimentally induced.
Although the recordings of the His potential have been shown to be very useful in the study of cardiac conduction and rhythm disturbances, there remain some problems regarding the clinical His bundle electrogram. Some of the studies were performed to solve in the perfused dog hearts and in situ dog hearts, and consequently the following results were obtained. In some experiments, recording of the His potential could not be achieved even in the perfused hearts in spite of the preserved A-V conduction, suggesting that, as experienced sometimes in the clinical cases, inability to record the His potential might not be due to the technical failure or the anatomical abnormalities of the His bundle. On the other hand, real "splitting of H" occurred in association with the increase in the duration and decrease in the amplitude of the His potential after the ligation of the anterior septal artery. In addition, the true Mobitz II type A-H block, and Wenckebach type intra-Hisian and H-V block could be produced experimentally.
Hiejima et al. (1975) studied this question.