title: Effects of metoprolol and amiodarone combination on heart rate, myocardial contractility and coronary flow: Study in isolated perfused rat hearts.
abstract: BACKGROUND
  Beta-blockers and amiodarone have been used concomitantly to treat arrhythmias associated with congestive heart failure. However, the combination of metoprolol and amiodarone has only been studied restrospectively, and its potential effects in congestive heart failure remain to be properly elucidated in prospective trials.
  
  
  OBJECTIVE
  The present investigation focused on evaluating the pharmacological interaction between metoprolol and amiodarone in an isolated perfused rat heart preparation.
  
  
  METHODS
  Adult male Wistar rats (n=24) were divided into four groups of six animals, and the effects of the metoprolol/amiodarone combination on systolic pressure, myocardial contractility (dP/dt), coronary flow (CF) and heart rate were analyzed, and the interdependent variables were compared.
  
  
  RESULTS
  There was a negative chronotropic effect by both metoprolol and the metoprolol/amiodarone combination in isolated rat hearts. However, the acute effects of the metoprolol/amiodarone combination showed no myocardial contractility depression or bradycardia accentuation compared with metoprolol alone. CF increased by 9.2% at minute 1 through minute 5 (P=0.004) with the metoprolol/amiodarone combination. There was no difference in systolic pressure or myocardial contractility among the groups.
  
  
  CONCLUSIONS
  The acute effects of the metoprolol/amiodarone combination in the isolated rat heart were an increase in CF, and no myocardial contractility depression or bradycardia accentuation.
authors.affiliation: Center of Research and PostGraduation - Cardiovascular Unit, Faculty of Medical Sciences of Minas Gerais, Belo Horizonte;
authors.forename: Wagner C
authors.initials: WC
authors.lastname: Pádua-Filho
authors.forename: David P
authors.initials: DP
authors.lastname: Brasil
authors.forename: Hueverson J
authors.initials: HJ
authors.lastname: Neves
authors.forename: Otoni M
authors.initials: OM
authors.lastname: Gomes
authors.forename: Edimar A
authors.initials: EA
authors.lastname: Bocchi