Complete Atrioventricular Block Due to Potassium

Intravenous infusion of KC1 at a rate of 1.22 or 2.45 mEq per minute to anesthetized dogs frequently resulted in complete A-V block at a time when P waves were still recorded in the ECG. Furthermore, some of the observations suggest that in hyperkalemia a regular idioventricular rhythm may not be essential for the diagnosis of complete atrioventricular (A-V) block. Thus, with complete A-V block induced during a rapidly changing plasma K+ , the ventricular pacemaker may be irregular.In addition, evidence was obtained that some parts of the atrial tissue, the automatic ventricular focus and the ventricular myocardium, are more resistant to K+ than is the A-V conduction tissue. The relative sensitivity of the various tissues of the heart seems to depend, among other factors, on the rate of KCl infusion.