Document Detail

Dynamic changes in the QT-R-R relationship during head-up tilt test in patients with vasovagal syncope.
MedLine Citation:
PMID:  15649233     Owner:  NLM     Status:  MEDLINE    
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.
Koichi Mizumaki; Akira Fujiki; Masao Sakabe; Kunihiro Nishida; Masataka Sugao; Takayuki Tsuneda; Hidehiko Nagasawa; Hiroshi Inoue
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Publication Detail:
Type:  Journal Article    
Journal Detail:
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:
Created Date:  2005-01-14     Completed Date:  2005-05-03     Revised Date:  2008-03-10    
Medline Journal Info:
Nlm Unique ID:  9607443     Medline TA:  Ann Noninvasive Electrocardiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  16-24     Citation Subset:  IM    
Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, Sugitani, Toyama, Japan.
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MeSH Terms
Adrenergic beta-Antagonists / pharmacology
Autonomic Nervous System / drug effects,  physiopathology*
Case-Control Studies
Chi-Square Distribution
Heart Rate / drug effects,  physiology*
Metoprolol / pharmacology
Syncope, Vasovagal / physiopathology*
Tilt-Table Test
Reg. No./Substance:
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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