Effects of Low and High Concentrations of Potassium on the Simultaneously Recorded Purkinje and Ventricular Action Potentials of the Perfused Pig Moderator Band

1968 Circulation Research  
The use of the perfused pig moderator band has allowed us to study the rapid simultaneous changes in Purkinje and ventricular action potentials induced by perfusing solutions of high (10 to 12 HIM) and low (0.6 to 0.8 HIM) K concentrations. High K shortened the plateau more in Purkinje fibers than in ventricular fibers and decreased the difference between the action potential durations of the two fiber types. Low K prolonged the plateau in Purkinje fibers but shortened it in ventricular fibers
more » ... ventricular fibers and increased the difference between the action potential durations. Low K initially hyperpolarized both Purkinje and ventricular fibers. However, the resting potential of the Purkinje fiber subsequently decreased as phase-4 depolarization increased. The decreased maximum repolarization potential associated with low K-induced pacemaker activity was time rather than voltage dependent. When the perfusate was changed from low K to control (K = 4.8 IIM), phase-4 depolarization was rapidly suppressed and the action potential of the Purkinje fiber was shortened to less than that produced by high K, and then changes in amplitude of the resting and action potentials occurred. Our observations help to explain some of the effects of low and high K on rhythm and conduction. ADDITIONAL KEY WORDS action potential plateau pacemaker resting potential maximum repolarization potential arrhythmia phase-4 depolarization Zwaardemaker-Librecht effect • Purkinje fibers have different electrophysiological properties than ventricular myocardial fibers (1-4). Spontaneous diastolic depolarization occurs normally in the Purkinje fibers but not in the ventricular fibers. In addition, the transmembrane action potentials of the Purkinje fibers have a greater amplitude, larger spike, more-.negative, rest- From the Schematic drawing of the moderator band preparation showing the arterial cannula inserted into the septal branch of the left anterior descending coronary artery. The action potentials of the Purkinje fiber were recorded from, the right bundle branch.
doi:10.1161/01.res.23.6.717 pmid:5727180 fatcat:bw26ewepbvhifgk7jaa3jkbiwi