Two Mechanisms of Cardiac Arrest Produced by Potassium

Abstract

Ventricular arrest occurs in isolated heart perfused with potassium-deficient solution when the extracellular potassium concentration is suddenly raised to a physiological concentration. This is known as a paradoxical phenomenon of Zwaardemaker and Libbrecht. Records of electrocardiograms, and ventricular and atrial transmembrane potentials from perfused rabbit hearts before, during and after this type of arrest revealed that its mechanism differs from the mechanism of cardiac arrest produced by an increase of external [K] above physiological concentration. The Zwaardemaker-Libbrecht phenomenon is associated with a striking increase in the velocity of repolarization while the typical effects of high-K concentration on the resting membrane potential and amplitude and upstroke velocity of the action potential are either very slight or absent. Conduction in the atria, ventricles and between the atria and the ventricles apparently is not disturbed during the Zwaardemaker-Libbrecht phenomenon; therefore, we attribute the cardiac arrest to a selective inhibition of the pacemaker activity. This might be due to an inhibition of the diastolic depolarization of the pacemaker fibers. A speculation is made that the type of imbalance between the intra- and extracellular K concentration in the myocardium which causes the Zwaardemaker-Libbrecht effect in the isolated heart could occur in situ and cause sudden death.

Influence of the lonic Environment on Spontaneous Electrical and Mechanical Activity of the Rat Portal Vein

“…When the [K + ] o is raised to the normal level again all discharge is inhibited and the membrane repolarizes. This is similar to the observation for heart muscle that return to normal K + -concentration from K + -low media is followed by a period of quiescence (22). It has been suggested that this inhibition is due to a sudden increase in the K-permeability Reduction or removal of calcium from the external medium changed the normal pattern of activity from one consisting of bursts of spikes to one consisting of single spikes at regular intervals, each spike preceded by a prepotential which resembled the diastolic depolarization of cardiac pacemaker cells.…”

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

“…The shortening was more than that produced by perfusion with the high K solution and was similar to the shortening of atrial and ventricular action potentials in the isolated perfused rabbit heart which occurred after a similar change in perfusing solution from low K to control (19). In the rabbit heart experiments, the change in perfusing solution was immediately followed by a cardiac arrest which lasted from 10 to 30 seconds.…”

“…In this study, the changes in the Purkinje and ventricular action potentials induced by the altered extracellular K concentrations occurred as rapidly as did the changes in the ventricular action potentials of the rabbit heart perfused by the Langendorf method with nearly identical solutions (10,18,19).…”

Assessment of blood pressure in cats presented with urethral obstruction

“…The cardiac toxicity of hyperkalemia is enhanced by hypocalcemia, 7 hyponatremia, 27 acidemia, 28 and the rate of elevation of the plasma potassium concentration. 21,29 In the hyperkalemic cats of this study, 67% (8/12) had concurrent acidemia, and 67% (8/12) had concurrent hypocalcemia. All of these cats were in the normotensive group.…”