Autonomic Modulation of the U Wave During Sympathomimetic Stimulation and Vagal Inhibition in Normal Individuals
- 18 November 2004
- journal article
- research article
- Published by Wiley in Pacing and Clinical Electrophysiology
- Vol. 27 (11) , 1484-1492
- https://doi.org/10.1111/j.1540-8159.2004.00665.x
Abstract
Prolonged repolarization time, an important contributor to the pathogenesis of ventricular arrhythmias, is usually identified by a long QT interval (QT) on the ECG but is frequently confounded by the presence of a U wave. The physiological basis and clinical relevance of the U wave is unresolved. To better understand the relationship between the T and U waves, this study examined their behavior during nonresting autonomic conditions. Twenty-five healthy subjects were evaluated during sympathomimetic infusion with isoproterenol and vagal inhibition with atropine. As heart rate (HR) increased in response to isoproterenol, the QU interval (QU) decreased by an eightfold greater extent than QT. Furthermore, a marked increase in U wave amplitude and decrease in T wave amplitude were observed with T and U wave fusion at higher HRs. During atropine, QU decreased by only a threefold greater extent than QT, T and U wave amplitudes were affected only minimally, and T-U wave fusion was not observed. These results demonstrate that sympathomimetic stimulation causes striking alterations in the timing and amplitude of U waves that differ from effects on the T wave. These effects are not observed during vagal inhibition. Thus, the U wave represents a component of cardiac repolarization that is electrocardiographically and physiologically distinct from the T wave with a unique response to sympathomimetic stimulation.Keywords
This publication has 28 references indexed in Scilit:
- Autonomic nervous system influences on qt interval in normal subjectsJournal of the American College of Cardiology, 2002
- The U wave and the M cellJournal of the American College of Cardiology, 1995
- QTc behavior during treadmill exercise as a function of the underlying QT-heart rate relationshipJournal of Electrocardiology, 1995
- The long QT syndromes: A critical review, new clinical observations and a unifying hypothesisProgress in Cardiovascular Diseases, 1988
- Cellular basis for the T wave of the electrocardiogramNature, 1976
- Purkinje repolarization as a possible cause of the U wave in the electrocardiogram.Circulation, 1975
- Effect of isoproterenol on the abnormal T waveThe American Journal of Cardiology, 1972
- XII. Polarity and Amplitude of the U Wave of the Electrocardiogram in Relation to that of the T WaveCirculation, 1957
- The U Wave of the ElectrocardiogramArchives of internal medicine (1960), 1955
- The duration of the Q-U interval and its components in electrocardiograms of normal personsAmerican Heart Journal, 1953