UNLABELLED: 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.
UNLABELLED: 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 LQT2patients observed at heart rates ≥ 60% of the predicted maximum (P < 0.05). LQT1patients demonstrated progressive or persistent QTc prolongation at higher heart rates, whereas LQT2patients 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: Lee W Gemma; Gregory M Ward; Mary M Dettmer; Jennifer L Ball; Peter J Leo; Danielle N Doria; Elizabeth S Kaufman Journal: J Cardiovasc Electrophysiol Date: 2011-06-02
Authors: Fabrice Extramiana; Pierre Maison-Blanche; Isabelle Denjoy; Patrick De Jode; Anne Messali; Jean-Philippe Labbé; Antoine Leenhardt Journal: Ann Noninvasive Electrocardiol Date: 2013-05-03 Impact factor: 1.468