Background
Defibrillation threshold (DFT) is the minimum energy required to successfully terminate
ventricular fibrillation. Epinephrine has been shown to increase the DFT in the beta-blocker
naïve, but using cardioselective beta-blockers leads to a reduction in the DFT on
infusion of epinephrine and norepinephrine. We sought to determine the impact of carvedilol
therapy on the DFT after infusion of epinephrine and norepinephrine.
Methods
DFT was determined in patients receiving carvedilol by the step-down method (baseline
DFT), and then patients (n = 27, 67.3 years, 70.0% were male, average left ventricular
ejection fraction = 19%) were randomized to a 7-minute infusion of norepinephrine,
epinephrine, or placebo in a double-blind manner. After the study drug infusion, DFT
testing was repeated (experimental DFT) and results were compared between groups.
Results
No differences in intragroup DFTs were observed among carvedilol-treated patients
receiving norepinephrine (9.4 ± 4.6 J vs 11.1 ± 7.8 J; P = .589), epinephrine (10.6 ± 5.3 J vs 9.8 ± 6.3 J; P = .779), or placebo (11.1 ± 7.0 vs 8.5 ± 4.2; P = .349).
Conclusions
Carvedilol prevents alterations in DFT produced by stress levels of catecholamines.
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Article info
Footnotes
This study was funded by a Hartford Hospital Research Grant.
Identification
Copyright
© 2008 Mosby, Inc. Published by Elsevier Inc. All rights reserved.
