Left ventricular performance during acute rate control in atrial fibrillation: the importance of heart rate and agent used.
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.
Pinter
Arnold
A
Division of Cardiology, St. Michael's Hospital, University of Toronto, Canada.
Dorian
Paul
P
Paquette
Miney
M
Ng
Alvina
A
Burns
Mark
M
Spanu
Ileana
I
Freeman
Michael
M
Korley
Victoria
V
Newman
David
D
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
D000889:Anti-Arrhythmia Agents; D004077:Digoxin; D004110:Diltiazem