A Case of a Cardiac Resynchronization Therapy-Defibrillator Exhibiting a Lower and Alternately Variable Basic Rate

Area of Science:

• Cardiology
• Biomedical Engineering
• Electrophysiology

Background:

• A 67-year-old male with cardiac sarcoidosis and severely impaired cardiac function received a cardiac resynchronization therapy defibrillator (CRT-D).
• The patient had a history of ventricular tachycardia, managed with catheter ablation, medication, and pacing, initially programmed in DDI mode.

Observation:

• Following admission for pneumonia and heart failure, the patient's CRT-D mode was changed from DDI to DDD due to atrial tachycardia causing inadequate biventricular pacing.
• The device exhibited prolonged and variable cycle lengths, leading to arrhythmias and exacerbated heart failure symptoms.

Findings:

• The noncompetitive atrial pacing (NCAP) algorithm, intended to prevent atrial tachycardia and ventriculoatrial (VA) synchrony, inadvertently induced rates lower than the programmed basic lower rate.
• Optimizing the AV delay to 120 ms and NCAP to 200 ms successfully mitigated these adverse events.

Implications:

• This case highlights a potential complication of the NCAP algorithm in CRT-D devices, particularly when programmed at high basic heart rates.
• Careful programming of AV delay and NCAP settings is essential to prevent device-induced arrhythmias and manage heart failure symptoms effectively.
• Further attention to NCAP algorithm behavior in specific patient populations and pacing configurations is warranted.