A Mechanism for Reentry in Canine Ventricular Tissue
In isolated canine papillary muscle-false tendon preparations it was possible by selecting the pattern of stimulation to obtain conduction block within the peripheral distribution of the Purkinje network. Action potentials recorded just proximal to the site of block were always extremely brief in duration; refractory periods were abbreviated accordingly. When propagation from specialized fibers to muscle fibers was made very critical, conduction block occurred at some Purkinje-muscle junctions while propagation continued through others. Under these conditions very early reentrant activity could be obtained in terminal Purkinje fibers. With proper timing, the impulse propagated back to the false tendon and emerged as a closely coupled extrasystole. Occasionally, the activity returned again to muscle and resulted in a double reentry. Electrotonic shortening of action potentials of Purkinje fibers at relatively long distances upstream from a site of block facilitated the reentry of proximal elements. Partial reentry of the Purkinje system created conditions favoring fractionation of the reentrant wave front.
- repetitive activity in ventricular tissue
- unidirectional conduction block
- abbreviation of action potentials
- refractory period of Purkinje fibers
- electronus in heart muscle
- Purkinje-muscle junctions
- cardiac arrhythmias
- Received August 26, 1970.
- Accepted November 3, 1970.
- © 1971 American Heart Association, Inc.