Pacemaker mediated tachycardias in single chamber rate responsive pacing.

Area of Science:

• Cardiology
• Biomedical Engineering

Background:

• Pacemaker-mediated tachycardia (PMT) is typically linked to dual-chamber pacemakers.
• Single-chamber, rate-responsive pacemakers can also develop PMT under specific conditions.

Observation:

• An 83-year-old man with complete atrioventricular block developed palpitations and pocket twitching post-implantation of a unipolar activity-sensing pacemaker.
• The pacemaker had flipped, causing diaphragmatic pacing that activated the rate-responsive sensor, initiating a positive feedback loop and tachycardia.

Findings:

• Pacemaker-mediated tachycardia occurred due to pacemaker flipping and subsequent pocket pacing activating the rate-responsive sensor.
• Reducing pacemaker output to 2.5 V successfully eliminated pocket pacing and the tachycardia.
• Pacemaker reversal necessitated a more sensitive setting for achieving adequate rate response during exercise.

Implications:

• Pacemaker flipping is a potential complication leading to PMT in single-chamber activity-sensing pacemakers.
• Strategies for preventing and managing pacemaker flipping are crucial.
• Understanding sensor-mediated tachycardias is important for device management.