title: Left ventricular performance during acute rate control in atrial fibrillation: the importance of heart rate and agent used.
abstract: BACKGROUND
  The relation between heart rate and left ventricular function during rate control in atrial fibrillation is incompletely understood.
  
  
  METHODS
  Twenty-four patients (age 67 +/- 11 years) with symptomatic recent onset rapid atrial fibrillation and rapid ventricular rate (> 110 bpm) were randomly assigned to receive either intravenous digoxin (13 mcg/kg) or intravenous diltiazem (0.25 mg/kg bolus plus a maintenance infusion). A portable radionuclide detector was used to collect validated measures of relative left ventricular volumes, along with heart rate data, every 15 seconds for 6 hours.
  
  
  RESULTS
  Heart rate decreased significantly at 15 minutes and 180 minutes in the diltiazem group (from 133 +/- 18 bpm to 111 +/- 26 bpm [P <.01] to 94 +/- 24 bpm [P <.001]) but not in the digoxin group (from 129 +/- 18 bpm to 126 +/- 17 bpm [P = NS] to 118 +/- 15 bpm [P = NS]). Left ventricular ejection fraction improved in both groups to a similar extent (from 39 +/- 10% to 50 +/- 8%, [P <.05] after diltiazem, and from 38 +/- 8% to 52 +/- 11% [P <.05] after digoxin at baseline vs 180 minutes, respectively). The ejection fraction vs heart rate slope was steeper in the digoxin group than in the diltiazem group (-0.34 +/- 0.18 vs -0.16 +/- 0.17, P =.048) indicating a more pronounced improvement in ejection fraction per unit decrease in heart rate.
  
  
  CONCLUSIONS
  In patients with acute atrial fibrillation, digoxin led to similar improvements in ejection fraction compared to diltiazem despite a slower and less potent heart rate slowing.
authors.affiliation: Division of Cardiology, St. Michael's Hospital, University of Toronto, Canada.
authors.forename: Arnold
authors.initials: A
authors.lastname: Pinter
authors.forename: Paul
authors.initials: P
authors.lastname: Dorian
authors.forename: Miney
authors.initials: M
authors.lastname: Paquette
authors.forename: Alvina
authors.initials: A
authors.lastname: Ng
authors.forename: Mark
authors.initials: M
authors.lastname: Burns
authors.forename: Ileana
authors.initials: I
authors.lastname: Spanu
authors.forename: Michael
authors.initials: M
authors.lastname: Freeman
authors.forename: Victoria
authors.initials: V
authors.lastname: Korley
authors.forename: David
authors.initials: D
authors.lastname: Newman
mesh_terms: D000368:Aged; D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000188:drug therapy*; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D004077:Digoxin / Q000008:administration & dosage / Q000627:therapeutic use*; D004110:Diltiazem / Q000008:administration & dosage / Q000627:therapeutic use*; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D016037:Single-Blind Method; D013318:Stroke Volume / Q000187:drug effects; D013997:Time Factors
chemical_list: D000889:Anti-Arrhythmia Agents; D004077:Digoxin; D004110:Diltiazem