| Dynamic changes in the QT-R-R relationship during head-up tilt test in patients with vasovagal syncope. | |
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MedLine Citation:
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PMID: 15649233 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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BACKGROUND: QT interval is influenced by preceding R-R intervals and autonomic nervous tone. Changes in QT intervals during vasovagal reflex might reflect autonomic modulation of ventricular repolarization; however, this issue has not been fully elucidated. This study aimed to evaluate dynamic response of QT interval to transient changes in R-R interval during vasovagal syncope (VVS) induced by head-up tilt test. METHODS: Eighteen patients with VVS and 18 age-and sex-matched controls were studied. All patients with VVS had a positive mixed-type response to head-up tilt and all controls had a negative response. CM5-lead digital electrocardiogram (ECG) was recorded and QT intervals were analyzed using Holter ECG analyzer. Using scatter plots of consecutive QT and the preceding R-R intervals, QT-R-R relations during tilt-up and tilt-back or during vasovagal reflex were independently fitted to an exponential curve: QT (second) = A + B x exp[k x R-R (second)]. RESULTS: During the tilt-up, A, B, and k did not differ between patients with VVS and controls. During the tilt back, k showed equivalent positive value compared to the tilt-up (4.1 +/- 1.3 vs -4.6 +/- 0.9) in controls. However, k remained negative (-1.3 +/- 1.5) during vasovagal reflex in patients with VVS. In six patients, in whom metoprolol was effective in eliminating VVS, QT-R-R relationship during the tilt-back became similar to that in controls. CONCLUSIONS: In patients with VVS, hysteresis of the QT-R-R relation is similarly shown during tilt-up as in controls, whereas this hysteresis is no longer evident and failure of QT prolongation is observed during VVS. |
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Authors:
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Koichi Mizumaki; Akira Fujiki; Masao Sakabe; Kunihiro Nishida; Masataka Sugao; Takayuki Tsuneda; Hidehiko Nagasawa; Hiroshi Inoue |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Annals of noninvasive electrocardiology : the official journal of the International Society for Holter and Noninvasive Electrocardiology, Inc Volume: 10 ISSN: 1082-720X ISO Abbreviation: Ann Noninvasive Electrocardiol Publication Date: 2005 Jan |
Date Detail:
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Created Date: 2005-01-14 Completed Date: 2005-05-03 Revised Date: 2008-03-10 |
Medline Journal Info:
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Nlm Unique ID: 9607443 Medline TA: Ann Noninvasive Electrocardiol Country: United States |
Other Details:
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Languages: eng Pagination: 16-24 Citation Subset: IM |
Affiliation:
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Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, Sugitani, Toyama, Japan. kmizu@ms.toyanna-mpu.ac.jp |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Adrenergic beta-Antagonists
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pharmacology Adult Autonomic Nervous System / drug effects, physiopathology* Case-Control Studies Chi-Square Distribution Electrocardiography Female Heart Rate / drug effects, physiology* Humans Male Metoprolol / pharmacology Syncope, Vasovagal / physiopathology* Tilt-Table Test |
| Chemical | |
Reg. No./Substance:
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0/Adrenergic beta-Antagonists; 37350-58-6/Metoprolol |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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