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Updated: Aug 12, 2026

Assessment of Vascular Tone Responsiveness using Isolated Mesenteric Arteries with a Focus on Modulation by Perivascular Adipose Tissues
Published on: June 3, 2019
Autonomic modulation of the U wave during phenylephrine and esmolol infusions
Anthony R Magnano1, Sarah Suleman, Hasan Garan
1Department of Medicine, Division of Cardiology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA. arm6@columbia.edu
Abstract:
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.
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