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

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Abstract
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.