Digitalis enhances exercise-induced hyperkalaemia.

In 9 patients with atrial fibrillation the effect of zero, low and high levels of serum digoxin on exercise-induced hyperkalemia was assessed by bicycle exercise tests. Exercise at each level of serum digoxin was associated with a significant (up to 20%) rise in plasma potassium. At a work load of 75 W the highest level of serum digoxin was associated with a significantly higher maximum plasma potassium concentration as compared to the maximum valueatazero serum digoxin. The enhancement of exercise-induced hyperkalemia may add to the arrhythmogenic effect of digitalis.