title: Dabigatran versus warfarin after bioprosthesis valve replacement for the management of atrial fibrillation postoperatively: protocol.
abstract: BACKGROUND
  Warfarin and similar vitamin K antagonists have been the standard therapy for patients with mechanical or biological valve prosthesis and atrial fibrillation (AF). Even with the appropriate use of therapy, some studies have reported that there is a high incidence of thromboembolic events, 1%-4% per year. Furthermore, a bleeding risk is significant, ranging from 2% to 9% per year, according to some studies.
  
  
  OBJECTIVE
  The objective of our study was to examine the effect of dabigatran etexilate versus dose-adjusted warfarin for the prevention of intracardiac thrombus in persistent or permanent AF at least 3 months after aortic and/or mitral bioprosthesis replacement.
  
  
  METHODS
  Dabigatran versus warfarin after bioprosthesis valve replacement for the management of atrial fibrillation postoperatively (DAWA) is a phase 2, prospective, open label, randomized exploratory pilot study. The main variable to be observed in this study is intracardiac thrombus. From August 2013 to April 2015, 100 patients, at least 3 months after aortic and/or mitral bioprosthesis replacement and permanent or persistent AF postoperatively, who match eligibility criteria will be selected from Ana Nery Hospital in Salvador-Bahia with a follow-up of three months. Patients were randomly assigned in a 1:1 ratio to receive either dabigatran etexilate or warfarin.
  
  
  RESULTS
  Although the present study has no statistic power to proof non-inferiority, it is expected that the dabigatran etexilate group will be protected as well as the warfarin group from intracardiac thrombus, without increasing the bleeding rates, since we are using safer doses (110 mg bid). The lack of necessity of monitoring INR is also another factor that contributes to a better adherence to the new drug and it can make all the difference in the manner of doing anticoagulation for patients with similar clinical characteristics.
  
  
  CONCLUSIONS
  The study is in the recruitment phase. It is possible that dabigatran etexilate is as effective as warfarin in preventing the emergence of intracardiac thrombus in patients with AF and mitral and/or aortic bioprosthesis.
  
  
  BACKGROUND
  Clinicaltrials.gov NCT01868243; http://clinicaltrials.gov/ct2/show/NCT01868243 (Archived by WebCite at http://www.webcitation/6OABiuasd).
authors.affiliation: Hospital Ana Nery, Serviço de Cardiologia, Universidade do Estado da Bahia, Salvador, Brazil. andreduraes@gmail.com.
authors.forename: Andre Rodrigues
authors.identifier: 0000-0002-1506-0327
authors.initials: AR
authors.lastname: Duraes
authors.forename: Pollianna Ds
authors.identifier: 0000-0002-7966-8550
authors.initials: PD
authors.lastname: Roriz
authors.forename: Fabio V
authors.initials: FV
authors.lastname: Bulhoes
authors.forename: Bianca DA
authors.initials: BD
authors.lastname: Nunes
authors.forename: Juliana Qv
authors.initials: JQ
authors.lastname: Muniz
authors.forename: Italvar Ndcr
authors.initials: IN
authors.lastname: Neto
authors.forename: Andre Ms
authors.initials: AM
authors.lastname: Fernandes
authors.forename: Francisco Jfbd
authors.initials: FJ
authors.lastname: Reis
authors.forename: Edmundo Jn
authors.initials: EJ
authors.lastname: Camara
authors.forename: Erenaldo Dsr
authors.initials: ED
authors.lastname: Junior
authors.forename: Deusdeth Ts
authors.initials: DTs
authors.lastname: Segundo
authors.forename: Felipe Pinho E Albuquerque
authors.identifier: 0000-0002-5705-4777
authors.initials: FP
authors.lastname: Silva
authors.forename: Roque
authors.initials: R
authors.lastname: Aras
keywords: anticoagulants; atrial fibrillation; dabigatran; hematologic agents; stroke; warfarin