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Repolarization dynamics during exercise discriminate between LQT1 and LQT2 genotypes.
MedLine Citation:
PMID:  20455992     Owner:  NLM     Status:  In-Process    
Abstract/OtherAbstract:
BACKGROUND: Repolarization dynamics during exercise in patients with long-QT Syndrome (LQTS) may be influenced by various factors such as a patient's genotype. We sought to systematically characterize the repolarization dynamics during exercise in patients with LQTS with a particular focus on the influence of genotype.
METHODS: Three groups of patients were studied on the basis of clinical status and genotype: LQT1, LQT2, and normal controls. Twenty-five age- and gender-matched patients were selected for each group. The QTc was measured during bicycle exercise testing and its dynamics were compared between the 3 groups.
RESULTS: The degree of QTc prolongation during exercise was greater in LQTS patients (LQT1 80 ± 47 ms, LQT2 64 ± 41 ms, Control 46 ± 20 ms, P = 0.02), with significant differences between LQT1 and LQT2 patients observed at heart rates ≥ 60% of the predicted maximum (P < 0.05). LQT1 patients demonstrated progressive or persistent QTc prolongation at higher heart rates, whereas LQT2 patients demonstrated maximum QTc prolongation at submaximal heart rates (50% of the predicted maximum) with subsequent QTc correction toward baseline values at higher heart rates. Importantly, these observations were consistent regardless of age, gender, or exercise type in subgroup analyses.
CONCLUSIONS: Reduced repolarization reserve in LQTS is genotype and heart rate specific.
Authors:
Raymond W Sy; Ishvinder S Chattha; George J Klein; Lorne J Gula; Allan C Skanes; Raymond Yee; Matthew T Bennett; Andrew D Krahn
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of cardiovascular electrophysiology     Volume:  21     ISSN:  1540-8167     ISO Abbreviation:  J. Cardiovasc. Electrophysiol.     Publication Date:  2010 Nov 
Date Detail:
Created Date:  2010-11-02     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9010756     Medline TA:  J Cardiovasc Electrophysiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1242-6     Citation Subset:  IM    
Copyright Information:
© 2010 Wiley Periodicals, Inc.
Affiliation:
Division of Cardiology, University of Western Ontario, London, Ontario, Canada.
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