Feb 1, 1986

Electrophysiological mechanisms underlying rate-dependent changes of refractoriness in normal and segmentally depressed canine Purkinje fibers. The characteristics of post-repolarization refractoriness

Circulation Research
J Davidenko, Charles Antzelevitch


Tissues from diseased hearts are known to exhibit post-repolarization refractoriness and rate-dependent changes of the refractory period that are often inconsistent with changes in action potential duration. To examine the electrophysiological mechanisms responsible for such rate-dependent changes of the refractory period, a narrow inexcitable zone was created by superfusing the central segments of Purkinje fibers with an "ion-free" isotonic sucrose solution. The degree of conduction impairment could be finely regulated by varying the resistance of the extracellular shunt pathway. At intermediate or low levels of block, the refractory period remained unchanged or decreased, respectively, as the rate was increased. At relatively high levels of block, however, we observed marked increases of the refractory period in response to increases in the stimulation rate. The disparity of refractoriness between normally conducting fibers and fibers exhibiting discontinuous conduction characteristics and post-repolarization refractoriness increased dramatically as a function of increasing stimulation rate. With the aid of current clamp techniques, we demonstrate that the differential behavior is due to the interplay between rate-dependent c...Continue Reading

Mentioned in this Paper

Structure of Purkinje Fibers
Biochemical Pathway
Depressed - Symptom
Action Potentials
PDZK1 gene
Refractory Period, Electrophysiological
Refractory Period
Body Surface Area Formula for Dogs
Clamping Activity

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