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Repolarization Dynamics During Exercise Discriminate Between LQT1 and LQT2 Genotypes
Author(s) -
SY RAYMOND W.,
CHATTHA ISHVINDER S.,
KLEIN GEORGE J.,
GULA LORNE J.,
SKANES ALLAN C.,
YEE RAYMOND,
BENNETT MATTHEW T.,
KRAHN ANDREW D.
Publication year - 2010
Publication title -
journal of cardiovascular electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.193
H-Index - 138
eISSN - 1540-8167
pISSN - 1045-3873
DOI - 10.1111/j.1540-8167.2010.01788.x
Subject(s) - medicine , qt interval , long qt syndrome , heart rate , repolarization , cardiology , genotype , prolongation , electrophysiology , blood pressure , biochemistry , chemistry , gene
Genotype and Exercise in LQTS . 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. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1242‐1246, November 2010)