Effect of chronic amiodarone therapy on defibrillation energy requirements in humans.
BACKGROUND
The effect of oral amiodarone therapy on defibrillation energy requirements in patients with an implantable defibrillator has not been established.


RESULTS
Twenty-one consecutive patients with implantable biphasic waveform defibrillators underwent a step-down determination of the defibrillation energy requirement 211 +/- 12 days before and 73 +/- 22 days after initiation of amiodarone therapy (mean total dose 26.7 +/- 11.1 g). Serum amiodarone and desethylamiodarone concentrations were measured at the time of defibrillation energy requirement determination. The mean defibrillation energy requirement before amiodarone therapy was 9.9 +/- 4.6 J. After initiation of amiodarone therapy, the mean defibrillation energy requirement increased to 13.7 +/- 5.6 J (P = 0.004). A linear relationship between the amiodarone (P = 0.02, r = 0.6), desethylamiodarone (P = 0.02, r = 0.6), and combined amiodarone-desethylamiodarone concentrations (P = 0.01, r = 0.6) and the defibrillation energy requirement was noted. Stepwise regression analysis demonstrated that the combined amiodarone-desethylamiodarone concentration was the only independent predictor of increase in the defibrillation energy requirement.


CONCLUSIONS
Chronic oral amiodarone therapy increases the defibrillation energy requirement by approximately 62% in patients with an implantable defibrillator. The combined amiodarone-desethylamiodarone concentration is directly related to the increase in the defibrillation energy requirement.
Department of Internal Medicine, University of Michigan Health System, Ann Arbor 48109-0022, USA. fpelosi@umich.edu
F
F
Pelosi
H
H
Oral
M H
MH
Kim
C
C
Sticherling
L
L
Horwood
B P
BP
Knight
G F
GF
Michaud
F
F
Morady
S A
SA
Strickberger
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000638:Amiodarone / Q000493:pharmacokinetics / Q000627:therapeutic use*; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use*; D017147:Defibrillators, Implantable; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged
D000889:Anti-Arrhythmia Agents; D000638:Amiodarone