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The effects of lidocaine on potassium efflux from various tissues of dog heart.

Publisised reports indicate that lidocaine is more effective in the treatment of ventricular than of atrial arrhythmias. It has also been reported that the drug shortens the action potentials of Purkinje and ventricular tissue, but not of atrial tissue. As part of an attempt to uncover the ionic basis for these differences, we studied the efflux of 42K from isolated strips of tissues from dog hearts. Lidocaine (2µg/ml) significantly enhaneed the efflux of 42K from ventricular strips and Purkinje fibers which had been previously loaded with the isotope for one hour. The drug did not accelerate the efflux of 42K from atrial tissue. It is suggested that the effects of lidocaine on pacemaker potentials and on the duration of action potentials (consequently the antiarrihythmic action) may be related to drug-induced increases in potassium counductance.