# Serendipitous Supernormality

## TL;DR

A patient with a heart condition experienced unusual heart rhythms due to a coincidental match between his pacemaker settings and his flutter rate, which was resolved by adjusting the pacemaker.

## Contribution

The paper highlights a rare case of supernormal conduction caused by a coincidental factorial relationship between pacing and flutter rates.

## Key findings

- A pacing rate of 85 bpm created a factorial match with the flutter rate, causing fixed-coupled supraventricular bigeminy and trigeminy.
- Changing the pacing rate to 75 bpm eliminated the abnormal rhythms.
- The phenomenon was due to the flutter waves aligning with the supernormal period of the ventricular myocardium.

## Abstract

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.

We describe supernormal conduction in a pattern of bigeminy or trigeminy due to serendipitous programming of the ventricular pacing rate at an exact factorial of the atrial flutter rate in a patient who underwent an ablate‐and‐pace strategy for recalcitrant atypical atrial flutter. Changing the ventricular pacing to a rate that was not an exact factorial of the flutter rate abolished this pattern.