Pacemaker repetitive nonreentrant ventriculoatrial synchronous rhythm. A review

Ventriculoatrial (VA) synchrony during dual chamber pacing can occur in any patient who has the ability to sustain repeated retrograde conduction. If the retrograde P wave is sensed, the result will be an endless loop tachyca rdia or repetitive reentrant VA synchrony. VA synchrony can also occur when a dual chamber pacemaker does not sense a retrograde P wave within the pos tventricular atrial refractory period. In this situation if the normally su prathreshold atrial stimulus at the end of the atrial escape interval is co ntinually delivered when the atrial myocardium is physiologically refractor y, the result will be a repetitive nonreentrant VA synchronous rhythm. Repe titive nonreentrant VA synchrony may produce unfavorable hemodynamic conseq uences and the pacemaker syndrome. It represents an example of functional a trial undersensing combined with functional loss of atrial capture. Managem ent requires modification of the programmed settings of the pacemaker and u tilization of certain algorithms designed for other functions but neverthel ess effective in this situation.