Reasons for loss of cardiac resynchronization therapy pacing: insights from 32 844 patients.

BACKGROUND: The efficacy of cardiac resynchronization therapy (CRT) is associated with the amount of CRT pacing delivered. The specific causes of CRT pacing loss and their relative frequencies remain poorly defined. METHODS AND
RESULTS: CRT patients who transmitted device data from 2006 to 2011 were screened for inclusion. Device diagnostics were analyzed using an automated algorithm to categorize CRT loss into 10 different causes. The algorithm was validated against manual adjudications using a portion of the entire cohort. There were 80 768 patients analyzed with a median time of 594 (interquartile range, 294-1003) days from implant to time of analysis. In this cohort, 40.7% of patients had <98% pacing, and 11.5% of patients had <90% pacing. For patients with <98% pacing, device diagnostics explained 55.8% of pacing loss: 30.6% atrial tachycardia/atrial fibrillation; 16.6% premature ventricular contractions; and 8.6% captured as episodes with at least 10 consecutive beats of CRT loss (ventricular sensing episodes). Inappropriately programmed sensed and paced atrioventricular (AV) intervals (SAV/PAV) accounted for 34.5% of all ventricular sensing episodes. As the severity of CRT loss increased, the contribution of atrial tachycardia/atrial fibrillation and SAV/PAV to the loss increased. Atrial tachycardia/atrial fibrillation accounted for >50% and premature ventricular contractions accounted for <10% of CRT loss in those with <90% CRT pacing.
CONCLUSIONS: CRT pacing <98% was observed in 40.7% of patients. Among those with suboptimal pacing, atrial tachycardia/atrial fibrillation was the most common reason for CRT pacing loss. Inappropriately programmed SAV/PAV intervals was the most common reason for episodes of sustained loss of CRT pacing. This information can help in defining more effective treatments to improve CRT delivery.