Propafenone induced acute variation of chronic atrial pacing threshold: a case report

A marked increase of chronic atrial pacing threshold resulting in loss of atrial capture, induced by propafenone, is reported in a patient with bradycardia-tachycardia syndrome. After atrial pacemaker implant, the atrial threshold had been measured repeatedly noninvasively and shown to be stable. The threshold rise and loss of atrial capture occurred after 7 days of treatment with propafenone at the dosage of 450 mg daily; drug withdrawal resulted in resumption of atrial capture and a return to prior pacing thresholds.