Serendipitous Supernormality

We describe a patient who underwent AV node modification to create complete heart block in the setting of incessant, ablation-and-drug-refractory, symptomatic atypical atrial flutter. His dual chamber defibrillator (previously implanted for resuscitated cardiac arrest) was programmed to the VVIR mode at a faster pacing rate of 85 bpm. Serendipitously, this rate was an almost exact factorial of his flutter rate of 250-260 bpm. This resulted in every 6th flutter wave falling in the supernormal period, resulting in fixed-coupled supraventricular bigeminy and trigeminy in the setting of complete heart block. Reprogramming the pacing rate to 75 bpm abolished bigeminy and trigeminy.