Presence and development of atrial fibrillation in chronic heart failure. Experiences from the MERIT-HF Study.
BACKGROUND
Atrial fibrillation is common in heart failure, but data regarding beta-blockade in these patients and its ability to prevent new occurrence of atrial fibrillation are scarce.


METHODS
Baseline ECGs in MERIT-HF were coded regarding baseline rhythm, and outcome was analyzed in relation to rhythm. Occurrence of atrial fibrillation during follow-up was also analyzed.


RESULTS
At baseline atrial fibrillation was diagnosed in 556 patients (13.9%). Mean metoprolol CR/XL dose in patients in atrial fibrillation (154 mg) and sinus rhythm (158 mg) was similar, as well as decrease in heart rate (14.8 and 13.7 bpm, respectively). Only 61 (total of 362) deaths occurred in those in atrial fibrillation at baseline, 31 on placebo and 30 on metoprolol (RR 1.0; 95% CI 0.61-1.65). During follow-up, new atrial fibrillation was observed in 85 patients on placebo and 47 patients on metoprolol (RR 0.53; 95% CI 0.37-0.76; p=0.0005).


CONCLUSIONS
First, given the wide confidence interval, it was impossible to detect an interaction between metoprolol and mortality in patients with atrial fibrillation and heart failure. Second, in patients with sinus rhythm at baseline, metoprolol reduced the incidence of atrial fibrillation during follow-up. However, we must be extremely cautious in over-interpreting effects in these subgroups.
van Veldhuisen
Dirk J
DJ
Department of Cardiology, Thoraxcenter, University Medical Center Groningen, PO Box 30 001, 9700 RB Groningen, The Netherlands. d.j.van.veldhuisen@thorax.umcg.nl
Aass
Halfdan
H
El Allaf
Dia
D
Dunselman
Peter H J M
PH
Gullestad
Lars
L
Halinen
Matti
M
Kjekshus
John
J
Ohlsson
Lis
L
Wedel
Hans
H
Wikstrand
John
J
D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage*; D000368:Aged; D001281:Atrial Fibrillation / Q000453:epidemiology* / Q000401:mortality / Q000517:prevention & control; D015897:Comorbidity; D004562:Electrocardiography; D005260:Female; D006333:Heart Failure / Q000453:epidemiology* / Q000401:mortality; D006801:Humans; D008297:Male; D008790:Metoprolol / Q000008:administration & dosage / Q000031:analogs & derivatives*; D008875:Middle Aged; D011446:Prospective Studies
D000319:Adrenergic beta-Antagonists; D008790:Metoprolol