CORRESPONDENCE: LETTER TO THE EDITOR
Continuation or Withdrawal of Beta-Blocker Therapy in Patients Admitted for Heart Failure
Alberto Bouzas-Mosquera, MD*,
Jesús Peteiro, MD, PhD and
Nemesio Álvarez-García, MD
* Department of Cardiology, Juan Canalejo Hospital, As Xubias, 84, 15006 A Coruña, Spain (Email: aboumos{at}canalejo.org).
We read with great interest the article by Fonarow et al. (1) evaluating the effect of continuation or withdrawal of beta-blocker drugs on outcomes in patients hospitalized with heart failure. The authors performed an analysis of 2,374 patients admitted with decompensated heart failure and concluded that withdrawal of beta-blocker therapy in these patients was associated with higher mortality.
There are several baseline characteristics that substantially differ among treatment groups. In addition to differences in the prevalence of coronary risk factors and coronary artery disease, patients who were withdrawn from beta-blocker drugs had lower left ventricular ejection fraction and higher expected post-discharge mortality risk. The authors performed a propensity score analysis to adjust for potential treatment selection bias.
Propensity scores represent the conditional probability of being assigned to a treatment group given a set of potential confounders (2,3). The bias and variance of the estimated effect of the treatment under study depend on the covariates selected for propensity score estimation. The authors claim that the propensity scores in their study were calculated with the set of all possible covariates that were related to the probability of receiving beta-blocker therapy; the inclusion of all information regarding the factors that might affect the selection of the treatment is, in fact, an important mainstay of propensity score analysis. However, the authors did not indicate which variables they used for estimation of the propensity scores. Furthermore, the reasons for beta-blocker withdrawal during hospital stay were not collected; this information is essential, because beta-blocker continuation or withdrawal might depend strongly on the clinical evolution of the patient during hospital stay, which in turn might be associated with outcome. Unfortunately, the authors also failed to provide information on the accuracy of the propensity scores for predicting treatment assignment, which might be assessed by the area under the receiver operating characteristic curve of the logistic regression model.
The presence of unmeasured variables that both affect the choice of the treatment and the outcome and the generation of propensity scores from potentially inaccurate models might preclude an adequate comparison among the different groups, which might compromise the validity of the estimated effect of the intervention.
 |
References
|
|---|
1. Fonarow GC, Abraham WT, Albert NM, et al. OPTIMIZE-HF Investigators and Coordinators Influence of beta-blocker continuation or withdrawal on outcomes in patients hospitalized with heart failure: findings from the OPTIMIZE-HF program J Am Coll Cardiol 2008;52:190-199.[Abstract/Free Full Text]2. Rubin DB. Estimating causal effects from large data sets using propensity scores Ann Intern Med 1997;127:757-763.[Abstract/Free Full Text] 3. D'Agostino Jr RB. Propensity scores in cardiovascular research Circulation 2007;115:2340-2343.[Free Full Text]
Related Article
-
Reply
- Gregg C. Fonarow, Jie Lena Sun, and Karen Pieper
J. Am. Coll. Cardiol. 2008 52: 2044-2045.
[Full Text]
[PDF]
|
Top
References