Pacemaker Wenckebach phenomenon due to antiarrhythmic drug toxicity

Two patients with intractable ventricular arrhythmia were managed with ventricular pacing and antiarrhythmic drugs. Toxic levels of these drugs results in unusual conduction disturbances at the level of Purkinje ventricular junction which caused pacemaker Wenckebach phenomenon and marked QRS prolongation. Sodium bicarbonate and sodium lactate infusion improved the conduction velocity probably by hyperpolarizing the membrane and reversed the conduction disturbance.