Electrical activation of the ventricular myocardium of the crocodile Crocodylus johnstoni: a combined microscopic and electrophysiological study

We mapped the sequence of ventricular depolarization in the crocodile Croco dylus johnstoni. We also attempted to find specialized conduction tissue wi thin the ventricular myocardium. Electrical recordings with miniature multi -point electrodes revealed two strands of rapidly conducting tissue (channe ls) within the interventricular septum, suggestive of conductive tissue pat hways. From these septal channels, wavefronts of excitation swept around ea ch ventricle. Electrical recordings did not indicate that there was conduct ive tissue in the wall of either ventricle. Similarly, microscopic studies of the septal channels provided no indication of specialized conductive tis sue. We suggest that the channels of early septal depolarization provide th e crocodile heart with a high speed depolarization pathway functionally ana logous to a rudimentary conductive system. (C) 1999 Elsevier Science Inc. A ll rights reserved.