Mode switching anomalies: A patient who remained symptomatic during paroxysmal atrial tachyarrhythmias despite a mode switching pacemaker

A patient with an automatic mode switching pacemaker continued to experience discomfort during the onset of poroxysmal supraventricular tachyarrhythmias. investigation revealed that the patient was sensing abrupt rate changes as the ventricular paced rate tracked the tachycardia during onset and detection phases. Her pacemaker was replaced with a new device with both mode switching and rate smoothing capabilities with resultant elimination of symptoms.