Complete atrioventricular block with unwidened QRS complex during hyperkalemia.

Purkinje and ventricular myocardial fibers are thought to be more sensitive to hyperkalemia than sinoatrial and atrioventricular (AV) nodes, although complete AV block due to hyperkalemia can occur. We describe a case in which hyperkalemia in a patient affected by renal failure is responsible for complete AV block without QRS complex prolongation. Temporary endoventricular pacing was essential in restoration of adequate renal blood flow and excretion of exceeding serum potassium with subsequent normalization of AV conduction.