Unexpected Response to Atrial Fibrillation Reduction in Patients With Cardiac Resynchronization Therapy

Background: Cardiac resynchronization therapy (CRT) is known to improve left ventricular (LV) systolic function and symptoms of systolic heart failure. The effect of CRT on atrial fibrillation (AF) burden is less clarified. Methods: 18 patients mean age of 77 ± 11 (72% male) underwent CRT implantations. There were no changes to concomitant anti-arrhythmic medication and permanent AF patients were excluded. Echocardiograms were obtained six month before and after device implantation. LV ejection fraction (LVEF), LV end diastolic dimension (LVEDd), left atrial (LA) dimension, and magnitude of mitral regurgitation (MR) were measured by echocardiogram before and after CRT. The burden of AF was evaluated by 24-hour Holter monitoring before and by device arrhythmic log after implantation. There were no concomitant medication changes. The results were later divided into presence (Group I) and absence (Group II) of paroxysmal or persistent AF. No patient was in permanent AF at the time of CRT implantation. Results: LVEF improved after CRT in both groups. Patients with AF showed the most beneficial effects of LVEF with average improvement of 41% (P-value=0.004) in comparison to 13% improvement in patients without AF (P-value=0.044). The LVEDd was improved by 11.9% in patients with AF (P-value=0.01) while it was improved by only 5.6% in patients without AF (P-value=0.08). LA Dimension was decreased by 4.4% in patients with AF (P-value=0.038). MR was reduced on average from moderate to mild for both groups. The number of AF episodes and duration of the AF were also decreased in all of our AF patients. The pre and post effect of CRT in patients with and without AF is shown in the table below: Conclusions: The AF burden in patients who received CRT was significantly reduced. There were excellent correlations between improvement of LVEF, LVEDd, LA dimension, and AF burden. This may be due to LV and LA remodeling. Further studies need to elaborate the mechanisms of this finding.