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      Utility of Corrected QT Interval in Orthostatic Intolerance

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          Abstract

          We performed this study to determine whether electrocardiographic corrected QT (QTc) interval predicts alterations in sympathovagal balance during orthostatic intolerance (OI). We reviewed 1,368 patients presenting with symptoms suggestive of OI who underwent electrocardiography and composite autonomic function tests (AFTs). Patients with a positive response to the head-up tilt test were classified into orthostatic hypotension (OH), neurocardiogenic syncope (NCS), or postural orthostatic tachycardia syndrome (POTS) groups. A total of 275 patients (159 OH, 54 NCS, and 62 POTS) were included in the final analysis. Between-group comparisons of OI symptom grade, QTc interval, QTc dispersion, and each AFT measure were performed. QTc interval and dispersion were correlated with AFT measures. OH Patients had the most severe OI symptom grade and NCS patients the mildest. Patients with OH showed the longest QTc interval (448.8±33.6 msec), QTc dispersion (59.5±30.3 msec) and the lowest values in heart rate response to deep breathing (HRDB) (10.3±6.0 beats/min) and Valsalva ratio (1.3±0.2). Patients with POTS showed the shortest QTc interval (421.7±28.6 msec), the highest HRDB values (24.5±9.2 beats/min), Valsalva ratio (1.8±0.3), and proximal and distal leg sweat volumes in the quantitative sudomotor axon reflex test. QTc interval correlated negatively with HRDB ( r = −0.443, p<0.001) and Valsalva ratio ( r = −0.425, p<0.001). We found negative correlations between QTc interval and AFT values representing cardiovagal function in patients with OI. Our findings suggest that prolonged QTc interval may be considered to be a biomarker for detecting alterations in sympathovagal balance, especially cardiovagal dysfunction in OH.

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          Most cited references43

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          Guidelines for the diagnosis and management of syncope (version 2009).

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            Consensus statement on the definition of orthostatic hypotension, pure autonomic failure, and multiple system atrophy. The Consensus Committee of the American Autonomic Society and the American Academy of Neurology.

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              QT dispersion: an indication of arrhythmia risk in patients with long QT intervals.

              Homogeneity of recovery time protects against arrhythmias whereas dispersion of recovery time is arrhythmogenic. A single surface electrocardiographic QT interval gives no information on recovery time dispersion but the difference between the maximum and minimum body surface QT interval may be relevant. This hypothesis was tested by measuring the dispersion of the corrected QT interval (QTc) in 10 patients with an arrhythmogenic long QT interval (Romano Ward and Jervell and Lange-Nielsen syndromes or drug arrhythmogenicity) and in 14 patients without arrhythmias in whom the QT interval was prolonged by sotalol. QTc dispersion was significantly greater in the arrhythmogenic QT group than in the sotalol QT group. In patients with prolonged QT intervals, QT dispersion distinguished between those with ventricular arrhythmias and those without. This supports the hypothesis that QT dispersion reflects spatial differences in myocardial recovery time. QT dispersion may be useful in the assessment of both arrhythmia risk and the efficacy of antiarrhythmic drugs.
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                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS One
                PLoS ONE
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, USA )
                1932-6203
                2014
                2 September 2014
                : 9
                : 9
                : e106417
                Affiliations
                [1 ]Department of Neurology, Korea University Medical Center, Korea University College of Medicine, Seoul, Korea
                [2 ]Department of Cardiology, Korea University Medical Center, Korea University College of Medicine, Seoul, Korea
                [3 ]Department of Neurology, Kyungsang University Medical Center, Jinjoo, Korea
                University of Texas Health Science Center at San Antonio, Research Imaging Institute, United States of America
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                Conceived and designed the experiments: JBK KJP BJK. Performed the experiments: JBK SWH. Analyzed the data: DHC JBK. Contributed reagents/materials/analysis tools: DHC. Wrote the paper: JBK JWP BJK.

                Article
                PONE-D-14-09183
                10.1371/journal.pone.0106417
                4152255
                25180969
                131ee051-7673-4bd9-90e0-f6ee3b1df27f
                Copyright @ 2014

                This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                History
                : 2 March 2014
                : 6 August 2014
                Page count
                Pages: 7
                Funding
                The authors have no support or funding to report.
                Categories
                Research Article
                Biology and Life Sciences
                Neuroscience
                Neural Homeostasis
                Physiology
                Electrophysiology
                Electrophysiological Properties
                Nervous System Physiology
                Medicine and Health Sciences
                Diagnostic Medicine
                Clinical Neurophysiology

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                Uncategorized

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