Background: Cardiac resynchronization therapy (CRT) has recently emerged as a new modality for the treatment of patients with advanced heart failure (HF).
Hypothesis: Cardiac resynchronization therapy reduces atrial and ventricular arrhythmia burdens.
Methods: We analyzed the clinical data of patients who underwent an upgrade from a dual-chamber to a biventricular implantable cardioverter-defibrillator (ICD) at a tertiary care center.
Results: Nineteen patients (age 67 +/- 10 years, 18 men, left ventricular [LV] ejection fraction 0.24 +/- 0.07) underwent an upgrade to CRT-ICD. The LV lead was placed in a lateral position in 11, posterolateral in 4, and anterolateral in 3 patients. Baseline New York Heart Association class of HF improved in 11 (58%) patients who were considered "responders." After adjusting for the duration of follow-up before and after the upgrade, the number of patients receiving any ICD therapy decreased significantly from 13 to 4 (p = 0.004) and the total number of therapies decreased from 72 to 17 (p = 0.067). Also, the number of detections of sustained ventricular arrhythmias decreased from 40 to 11 episodes (p = 0.05), but the decrease in the number of detected supraventricular arrhythmias and mode switch episodes was not significant. The reduction in the ventricular arrhythmia load was independent of whether or not the patient responded to CRT.
Conclusion: Our data suggest that CRT reduces ventricular but not atrial arrhythmia burden in patients with HF irrespective of their clinical response. This suggests that the reduction in arrhythmia is primarily an electrical phenomenon. Further studies are needed to confirm these findings and to uncover their underlying mechanisms.