Cardiac Resynchronization Therapy Response is Associated with Shorter Duration of Atrial Fibrillation NICOLAS LELLOUCHE, M.D., CARLOS DE DIEGO, M.D., MARMAR VASEGHI, M.D., ERIC BUCH, M.D., DAVID A. CESARIO, M.D., PH.D., AMAN MAHAJAN, M.D., PH.D., ISAAC WIENER, M.D., GREGG C. FONAROW, M.D., NOEL G. BOYLE, M.D., PH.D., and KALYANAM SHIVKUMAR, M.D., PH.D. From the UCLA Cardiac Arrhythmia Center, Division of Cardiology, Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California Background: Atrial fibrillation (AF) is commonly associated with heart failure. The benefit of cardiac resynchronization therapy (CRT) on atrial remodeling has been demonstrated. However, biventricular pacing did not reduce the global incidence of AF. We evaluated the relationship between CRT response and AF duration. Methods: We retrospectively analyzed data from 96 patients (59 ± 15 years; 78% male) who under- went CRT. All patients had class III–IV New York Heart Association (NYHA) symptoms despite maximal medical therapy, left ventricular ejection fraction (LVEF) ≤ 35%, QRS >130 ms, and sinus rhythm before implantation. CRT response in patients who survived at six months of follow-up was defined as: (1) no hospitalization for heart failure and (2) improvement of one or more grades in the NYHA classification. Results: CRT responders (n = 54) and non-responders (n = 42) had similar baseline characteristics, including the incidence of persistent AF within six months before implantation. Six months after implan- tation, when compared to baseline, CRT responders exhibited a significant decrease in left atrial size (47.5 ± 7.1 mm vs 44.6 ± 7.7 mm, P < 0.01) and in the incidence of persistent AF (17% vs 2%, P = 0.02). At six months, CRT responders demonstrated shorter mean AF duration (7.5 ± 43.3 hours vs 48.8 ± 129.0 hours, P = 0.03) and lower incidence of persistent AF (2% vs 19%, P = 0.004) compared to nonresponders. Conclusion: CRT response is associated with a reversal of atrial remodeling and a shorter AF duration. (PACE 2007; 30:1363–1368) cardiac resynchronization therapy, atrial fibrillation duration Introduction Atrial fibrillation (AF) is frequently associ- ated with heart failure (HF) 1 and is an indepen- dent risk factor for morbidity and mortality in this population. 2–3 The prevalence increases from 10% in patients with New York Heart Association (NYHA) functional class II up to 50% in those with NYHA functional class IV. 1 Cardiac resynchro- nization therapy (CRT) is currently an established treatment of severe HF associated with cardiac dyssynchrony for patients in sinus rhythm 4–6 or in chronic AF with well-controlled heart rate. 7–9 However, AF could worsen left ventricular func- tion, 1 affecting the clinical benefit of CRT. Dr. Nicolas Lellouche is supported by grants from the French Society of Cardiology, Dr. Kalyanam Shivkumar is supported by grants from American Heart Association and the NHLBI (R01HL084261). Address for reprints: Noel G. Boyle, M.D. Ph.D., UCLA Car- diac Arrhythmia Center, Division of Cardiology, Department of Medicine, BH 407 CHS, David Geffen School of Medicine at UCLA, 10833 Le Conte Avenue, Los Angeles, CA 90095-1679. Fax: 310-794-6492; e-mail: nboyle@mednet.ucla.edu Received May 20, 2007; revised June 30, 2007; accepted July 30, 2007. CRT has been shown to reverse atrial remod- eling. 10 Nevertheless, CRT did not influence AF incidence in the CARE-HF study. 11 The relation- ship between AF duration and CRT response has not been specifically analyzed. Thus the aim of this study was to evaluate the association between CRT response and AF duration. Methods We retrospectively studied patients who were referred to our center for CRT between January 2003 and June 2005. Persistent AF Definition Persistent AF was defined according to the international classification 12 as AF requiring an intervention for termination (pharmacological or electrical cardioversion). Inclusion Criteria The inclusion criteria in our study were: • Chronic HF • NYHA functional class III or IV HF symp- toms despite optimal medical therapy as defined by current guidelines 13 C 2007, The Authors. Journal compilation C 2007, Blackwell Publishing, Inc. PACE, Vol. 30 November 2007 1363