The control of atrial contraction by ventriculo-atrial pacing in the dog with AV block

Atrial contraction in dogs with atrioventricular (AV) block was controlled by multiple atrial stimuli delivered during ventricular diastole. Acute hemodynamic changes were assessed. At a ventricular rate of 60 bpm, the spontaneous atrial rate averaged 83, and atrial cannon waves were frequent. When the atria were given two stimuli at an interval of 500 ms during ventricular diastole, the cannon waves were eliminated completely, and a fall in mean central venous pressure and a rise in systemic blood pressure were found. At a pacing rate of 90 bpm, similar changes in the cannon waves, mean central venous pressure, and systemic blood pressure were found when two atrial stimuli followed ventricular stimulation. Ventriculo-atrial multiple pacing may be useful in both clinical and experimental AV block.