Rapid atrial pacing above the maximum sensor rate: a case report

Area of Science:

• Cardiology
• Biomedical Engineering
• Electrophysiology

Background:

• Ventricular-based timing modes in pacemakers can lead to elevated atrial pacing when intrinsic atrioventricular (AV) conduction is shorter than the programmed AV delay.
• A previous case report in 2015 described rapid atrial pacing in a DDI-mode pacemaker induced by premature atrial complexes and slow AV conduction.

Observation:

• A patient with a St. Jude Abbott DCPPM pacemaker (DDDR mode) experienced rapid atrial pacing exceeding 180 bpm.
• This event was triggered by an atrial tachyarrhythmia that caused a mode switch to DDIR, utilizing ventricular-based timing.
• The rapid atrial pacing episode terminated spontaneously.

Findings:

• The phenomenon was precipitated by an atrial tachyarrhythmia leading to a mode switch to DDIR.
• Rate-responsive pacing, enabled on the device, shortened the calculated ventriculo-atrial interval (VAI) sufficiently.
• This shortened VAI, combined with slow AV conduction, facilitated pacemaker 'crossover' and induced rapid atrial pacing.

Implications:

• Understanding this unusual mechanism requires careful analysis of pacemaker timing cycles and programming limitations.
• This case highlights a unique interaction between device settings (rate-responsiveness, mode switching) and patient electrophysiology.
• The serendipitous nature of this event underscores the complexity of pacemaker behavior in specific clinical scenarios.