Relationship between Potassium and Vagal Action on Atrioventricular Transmission.

Interrelationship of Potassium and Vagal Action on the Sinoatrial Pacemaker and on Atrioventricular Conduction.

Sympathetic and periodic vagal influences on antegrade and retrograde conduction through the canine atrioventricular node.

Concurrent stimulation of the parasympathetic and sympathetic branches of the autonomic nervous system causes a diminished sympathetic response at high levels of vagal activity. This "accentuated antagonism" has been demonstrated for cardiac chronotropic, inotropic, and dromotropic responses. The effect on conduction was demonstrated with tonic stimulation of the vagus nerve. However, normally ...

On the cause of ventricular asystole during vagal stimulation.

In anesthetized dogs the vagus nerve was stimulated for 2 min; during the first minute the ventricles were driven at a rate higher than the control sinus rate; after discontinuation of the drive, the duration of asystole was prolonged. When the ventricles were driven at a rate lower than the sinus rate during vagal stimulation the subsequent asystole was shortened. Slowing sinus activity by gra...

On the mechanism of idioventricular pacemaker suppression by fast drive.

The role of vagal activity, potassium concentration, and temperature in overdrive suppression of ventricular pacemakers, was studied in anesthetized dogs with and without surgical atrioventricular block. The results were as follows. (1) Overdrive of an idioventricular pacemaker during vagal stimulation was followed by a second pause. (2) Hypothermia increased the duration of the vagal and overd...

Electrophysiological mechanisms and determinants of vagal maneuvers for termination of paroxysmal supraventricular tachycardia.

BACKGROUND The vagal maneuvers used for termination of paroxysmal supraventricular reentrant tachycardia (PSVT) appear to involve more complex mechanisms than we have known, and further study should be done to explore the possible mechanisms. METHODS AND RESULTS In this study, 133 patients with PSVT and 30 age- and sex-matched control subjects were included. We assessed the effects of differe...