Repolarization interactions between cardiac segments of varying action potential duration.
We studied interactions between action potential duration (APD) disperse zones using a double compartment bath in which an APD lengthening solution (Ni++ 2 mmol/L, in Tyrode's solution) was added to one compartment (which contained a portion of the fiber labeled "segment A") followed by addition of an APD shortening solution (6 to 10 mmol/K+) to the other compartment ("segment B"). Standard microelectrode techniques were used in canine Purkinje fibers. With Ni++ in segment A, there was a dispersion in APD measured at both 50% (APD50) and 95% (APD95) of repolarization. After selective addition of K+ to segment B, APD50 dispersion remained constant while APD95 dispersion increased, which indicated a change in the slope of repolarization, a factor with possible arrhythmogenic potential. In addition, a characteristic transitional action potential was seen adjacent to the partition. This had a timely and normally sloping early repolarization followed by a much more gradually sloping shelf. Premature action potentials arising during this shelf had diminished upstrokes. Results of these experiments may be useful in evaluating APD dispersion in relation to arrhythmias.
Duo
G S
GS
Department of Medicine, Mount Sinai School of Medicine, City University of New York.
Hoff
P
P
Kupersmith
J
J
D000200:Action Potentials; D000818:Animals; D004285:Dogs; D004594:Electrophysiology; D006329:Heart Conduction System / Q000502:physiology*; D066298:In Vitro Techniques; D009532:Nickel; D011188:Potassium / Q000502:physiology; D011690:Purkinje Fibers / Q000502:physiology*
D009532:Nickel; D011188:Potassium