T wave of normo- and hyperkalemic canine heart: Effect of vagal stimulation

The effect of vagal stimulation on ventricular repolarization of normokalemic and hyperkalemic canine hearts was investigated. During the normokalemic state stimulation of the vagus decreased the amplitude of the T wave when the polarity of the wave prior to vagal activity was upright. When the control T waves were biphasic or inverted the effect of vagal stimulation was an increase in negativity. In all cases the T waves became upright and increased in amplitude during potassium (K+) infusion regardless of the initial T configuration prior to the infusion of the cation. As the plasma K+ levels were increasing the amplitude of these heightened T waves was further enhanced by vagal stimulation. It is concluded that vagal activity does effect ventricular repolarization and this effect is exaggerated as the plasma K+ level is progressively elevated.