The nature and type of arrhythmias in acute experimental hyperkalemia in the intact dog

Abstract

Progressive A-V block was produced in the intact dog by rapid intravenous infusion of isotonic potassium chloride (KCl) solution. The site of the conduction disturbance was determined with electrode catheter recordings from the atria and region of the His bundle, and a simultaneous conventional ECG. First-degree and seconddegree A-V block and then complete A-V dissociation were produced, with the block above the bundle of His, the ventricles following a pacemaker originating in the bundle of His. During A-V dissociation, atrial potentials maintained their control rate. “Sinoventricular” conduction could not be produced under the conditions of the experiments. Further infusion of KCl produced conduction defects below the bundle of His with an irregular ventricular action. Unexpectedly, with the most rapid infusions of KCl, the experimental animals developed complete block below the site of the His bundle recording at a time when conduction above the junctional pacemaker was only partially blocked. Ventricular arrhythmias, including terminal tachycardias, are probably the consequence of depressed or failing propagation of the cardiac impulse.