Purpose: Competitive athletes have often a prolonged QT interval. Currently, genetic test is used to distinguish healthy athletes from LQT1/LQT2 patients, but it is expensive, it takes long timeline and it is negative in about 30% of cases with clinical diagnosis of long QT Syndrome. Aim of the study was to evaluate whether the trend of QT hysteresis could be used as a new diagnostic method to distinguish healthy athletes from LQTS subjects and to hypothesize the involved gene (LQT1, LQT2). Methods: Four groups of subjects were created. LQT1: 6 subjects (mean age 24±13 years) with prolonged QT interval at rest ECG (QT: 510±67 ms) and positive genotype (KCNQ1 mutation). LQT2: 5 subjects (mean age 20±3 years) with prolonged QT interval (QT: 490±56 ms) and positive genotype (KCNH2 mutation). ATHLETES (ATH): 6 competitive sport athletes (mean age 15±3 years) sent from the Sport Medicine Institute for further investigations after the recognition of a prolonged QT interval at basal ECG (QT: 480±52 ms) or during exercise test; all of them had negative genotype. Any group was compared with a control group (CTRL) with normal QT interval at resting ECG: CTRL-LQT1/2 consisted of 19 subjects (mean age 18±5 years); CTRL-ATH consisted of 16 athletes (mean age 16±3 years). All subjects underwent treadmill exercise test according to Bruce protocol. Hysteresis was calculated subtracting the QT interval measured at 80, 100 and 120 bpm during exercise from the QT interval at the same heart rate (HR) into the recovery phase. QT and QTc values were expressed as mean ± standard deviation and compared using Student's t test. Results: In LQT1 group the QT hysteresis resulted significantly greater compared to CTRL group at all HR considered (p<0.001 at 80, 100 and 120 bpm). Also in LQT2 group the QT hysteresis was significantly different from that of the CTRL (p<0.001 at all the HR considered). There was also a significant difference in QT hysteresis between LQT1 and LQT2 groups at all HR considered (p<0.01). Moreover QT hysteresis in the LQT2 group had a positive value differently from all the other groups, in which it was negative. In ATH group QT hysteresis behaviour was similar to the CTRL group (p=NS at all the HR considered). The QT hysteresis was significantly different between LQT1 and ATH group at 100 and 120 bpm (p=0.05 and p=0.02). It was also different between LQT2 and ATH group at all the HR considered (p<0.03). Conclusions: Our results show that QT hysteresis analysis allows to distinguish healthy athletes with prolonged QT interval from patients with LQT syndrome and LQT1 from LQT2 patients.
Athletes with prolonged QT interval: is QT hysteresis analysis a useful method to distinguish healthy athletes from LQTS patients?
GIUSTETTO, Carla;CERRATO, Natascia;SCROCCO, Chiara;GAITA, Fiorenzo
2014-01-01
Abstract
Purpose: Competitive athletes have often a prolonged QT interval. Currently, genetic test is used to distinguish healthy athletes from LQT1/LQT2 patients, but it is expensive, it takes long timeline and it is negative in about 30% of cases with clinical diagnosis of long QT Syndrome. Aim of the study was to evaluate whether the trend of QT hysteresis could be used as a new diagnostic method to distinguish healthy athletes from LQTS subjects and to hypothesize the involved gene (LQT1, LQT2). Methods: Four groups of subjects were created. LQT1: 6 subjects (mean age 24±13 years) with prolonged QT interval at rest ECG (QT: 510±67 ms) and positive genotype (KCNQ1 mutation). LQT2: 5 subjects (mean age 20±3 years) with prolonged QT interval (QT: 490±56 ms) and positive genotype (KCNH2 mutation). ATHLETES (ATH): 6 competitive sport athletes (mean age 15±3 years) sent from the Sport Medicine Institute for further investigations after the recognition of a prolonged QT interval at basal ECG (QT: 480±52 ms) or during exercise test; all of them had negative genotype. Any group was compared with a control group (CTRL) with normal QT interval at resting ECG: CTRL-LQT1/2 consisted of 19 subjects (mean age 18±5 years); CTRL-ATH consisted of 16 athletes (mean age 16±3 years). All subjects underwent treadmill exercise test according to Bruce protocol. Hysteresis was calculated subtracting the QT interval measured at 80, 100 and 120 bpm during exercise from the QT interval at the same heart rate (HR) into the recovery phase. QT and QTc values were expressed as mean ± standard deviation and compared using Student's t test. Results: In LQT1 group the QT hysteresis resulted significantly greater compared to CTRL group at all HR considered (p<0.001 at 80, 100 and 120 bpm). Also in LQT2 group the QT hysteresis was significantly different from that of the CTRL (p<0.001 at all the HR considered). There was also a significant difference in QT hysteresis between LQT1 and LQT2 groups at all HR considered (p<0.01). Moreover QT hysteresis in the LQT2 group had a positive value differently from all the other groups, in which it was negative. In ATH group QT hysteresis behaviour was similar to the CTRL group (p=NS at all the HR considered). The QT hysteresis was significantly different between LQT1 and ATH group at 100 and 120 bpm (p=0.05 and p=0.02). It was also different between LQT2 and ATH group at all the HR considered (p<0.03). Conclusions: Our results show that QT hysteresis analysis allows to distinguish healthy athletes with prolonged QT interval from patients with LQT syndrome and LQT1 from LQT2 patients.
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