[Increase in blood potassium and subsequent normalization: effects on the electrocardiogram. Case report].

Significant variations in the ECG have been observed in a female aged 77 with heart failure and chronic atrial fibrillation during an occasional increase in blood potassium followed by normalization. The major phenomena observed during hyperkalemia, due to a severe dehydration, were a transient sinus rhythm with atrio-ventricular block followed by atrial activity disappearance and advent of interventricular and fascicular block. Therapeutic normalization of blood potassium leads to a progressive disappearance of intraventricular and fascicular block, a temporary sinus rhythm and finally the return to atrial fibrillation which was the steady state of the patient before the blood potassium imbalance.