[Atrioventricular asynchrony and pacing].

Atrioventricular dissociation and atrioventricular block are the most common types of atrioventricular asynchrony. Less frequently, atrioventricular asynchrony may occur in the pacemaker syndrome or during sequential pacing with programmed asynchronous atrioventricular delay. A rare type of atrioventricular asynchrony that has relevant hemodynamic effects is observed in first-degree atrioventricular block when associated with mitral stenosis or other conditions characterized by an obstruction of the left atrial outflow. Atrioventricular asynchrony can be defined as systolic when both the atrium and ventricle are contracting simultaneously (pacemaker syndrome, sequential pacing with programmed asynchronous atrioventricular interval), or systo-diastolic when atrial systole occurs at the onset of ventricular diastole as observed in patients with very long PR interval. All described asynchronies can be eliminated by sequential pacing with programmed synchronous atrioventricular delay.