Reasons for Loss of Cardiac Resynchronization Therapy Pacing

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 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.