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The Impact of Catecholamines on Defibrillation Threshold in Patients with Implanted Cardioverter Defibrillators
Author(s) -
KALUS JAMES S.,
WHITE C. MICHAEL,
CARON MICHAEL F.,
GUERTIN DANETTE,
MCBRIDE BRIAN F.,
KLUGER JEFFREY
Publication year - 2005
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1111/j.1540-8159.2005.09484.x
Subject(s) - medicine , epinephrine , defibrillation threshold , placebo , ventricular fibrillation , norepinephrine , beta blocker , sedation , cardiology , anesthesia , heart failure , dopamine , alternative medicine , pathology
Objectives: To determine the effect of physiologic catecholamine concentrations on the defibrillation threshold (DFT) in patients with implanted cardioverter defibrillators.Background: DFT is the minimum energy delivered by an implanted cardioverter defibrillator that successfully converts ventricular fibrillation. DFT testing is performed under conscious sedation. Since activities of daily living enhance sympathetic tone substantially over these nadir levels, it is important to explore the impact of catecholamines on DFT.Methods: In this double‐blind study, we determined DFT by the step‐down method. Patients (n = 50) were stratified by beta‐blocker use and then randomized to a 7‐minute infusion of epinephrine, norepinephrine, or placebo. After study infusion, DFT testing was repeated. Changes in DFT with different study medications were compared. Subgroup analyses of the effects of catecholamines on DFT, based on beta‐blocker use, were also performed.Results: Norepinephrine reduced DFT from baseline measurements by 22.6% (P = 0.008). Neither epinephrine nor placebo impacted DFT (P = 0.999, P = 0.317, respectively). In the subgroup analyses, DFT was reduced with norepinephrine regardless of beta‐blocker use, while epinephrine reduced DFT among those receiving beta‐blockers. No change in DFT was observed in either of the placebo subgroups.Conclusions: Elevation of plasma norepinephrine concentrations reduces the DFT, while elevations in epinephrine had no effect. Norepinephrine seems to reduce DFT regardless of beta‐blocker therapy but epinephrine's effects are beta‐blocker dependent.