Discrete zones of the electrical connexion of Purkinje terminals with muscle fibres in the canine ventricle

The authors have recorded the activity of the Purkinje terminals (P) and the adjacent muscle (M) fibres in different portions of the right ventricle of the dog. It is shown that the transmission of excitation from P to the M fibres is observed not over the whole endocardial surface but only at discrete sites-zones of the P-M interaction. The zones have the form of ellipses with axes of 300 × 100 μm and are located relatively far from each other-at a distance of 800 to 2000 μm. The total area of the zones is ~ 5 per cent of the endocardial surface. The P-M delay is less within the zone of connexion of P-M fibres (4 msec) and greater outside it (up to 10 msec).