Tracking of atrial flutter during DDD pacing: another form of pacemaker-mediated tachycardia.

Two patients who had DDD pacemakers inserted for symptomatic sick sinus syndrome developed sustained upper-rate limit pacing. It was demonstrated in these two patients that pacemaker-mediated tachycardia was due to tracking of atrial flutter. DDD pacemakers should be used with caution in patients with the sick sinus syndrome and associated atrial tachyarrhythmias. Medical treatment of recurrent atrial tachyarrhythmias may allow patients to remain in the DDD mode.