Autonomic modulation of the U wave during phenylephrine and esmolol infusions.
The etiology of U waves on the electrocardiogram is uncertain. We previously found that U waves could be amplified by isoproterenol infusion. Whether other autonomic interventions modify U-wave amplitude is unknown. Twenty-five healthy subjects underwent graded infusions of esmolol and phenylephrine. Heart rate, T-wave amplitude, U-wave amplitude, and QT and QU intervals were measured using interactive computerized electrocardiogram software. Heart rate decreased with both interventions ( P < .001), though to a greater degree with phenylephrine. U-wave amplitude increased by 16.3% during phenylephrine ( P < .001) but decreased by 14.5% during esmolol ( P < .001). The change in U-wave amplitude was strongly dose-dependent for both phenylephrine ( P < .001) and esmolol ( P < .001). T-wave amplitude increased with phenylephrine (597-692 microV, P < .001) but decreased with esmolol (632-568 microV, P < .001). QT and QU intervals increased with both interventions ( P < .001). We conclude that sympathetic and parasympathetic activities are important determinants of U-wave timing and amplitude.
Magnano
Anthony R
AR
Department of Medicine, Division of Cardiology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA. arm6@columbia.edu
Suleman
Sarah
S
Garan
Hasan
H
Bloomfield
Daniel M
DM
D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage* / Q000494:pharmacology; D000328:Adult; D004562:Electrocardiography / Q000187:drug effects*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D010656:Phenylephrine / Q000008:administration & dosage* / Q000494:pharmacology; D011412:Propanolamines / Q000008:administration & dosage* / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D011412:Propanolamines; D010656:Phenylephrine; C036604:esmolol