The effects of smoking on myocardial conduction in the human heart.

Inhalation of a few puffs on a cigarette increases the velocity of conduction and shortens the effective refractory period of the A-V node. These effects are attributed to adrenergic stimulation produced by minute amounts of nicotine absorbed. Wenckebach block is abolished whether induced by atrial pacing or occurring spontaneously. Conduction velocity in the His-Purkinje system and in the anomalous pathways in the WPW syndrome were not affected. Smoking increases the ventricular rate in atrial fibrillation, and antagonizes the cholinergic effects of digitalis.