PDF(Pubmed)
Abstract：
BACKGROUND: Measurement of the QT interval in the ECG (QT interval) is important in evaluating risk for cardiac death and for assessing the impact of drugs on the heart. The objective of this study is to determine whether the time of day affects the QT interval, QT interval variability and whether these relationships are influenced by an individual\'s sex.
METHODS: Twenty-four hour ECGs were analyzed in detail on 50 individuals, 49 years of age, without evidence of coronary artery disease, structural heart disease, or significant arrhythmias. Four different QT-heart rate adjustment formulae were calculated and compared.
RESULTS: There were significant (P=0.0014) differences between the QT-heart rate relationship during three different time-periods (night 00:00 to 08:00 h, day 08:00 to 14:00 h and evening 14:00 to 24:00 h). Women, compared to men, had a steeper relation of QT to RR interval indicating that when heart rate slows at night, the QT interval is more prolonged which is consistent with a greater susceptibility to fatal arrhythmias. The variability of the QT interval (the SD) was significantly (P<0.01) greater in men than women at night and in the evening but not during the day. There were differences in the ability of different QT heart rate adjustment formulae to blunt the effect of heart rate changes on the QT interval during the day.
CONCLUSIONS: The time of the day that the QT interval is assessed should be considered. The QT heart rate relationship is different in women than in men especially at night. QT interval variability is greater at night especially in men. There are differences in the ability of QT heart rate adjustment formulae to blunt the effect of heart rate on the QT interval. Differences in the QTc at night might be the basis for the higher prevalence of sudden death in women at night.
METHODS: Twenty-four hour ECGs were analyzed in detail on 50 individuals, 49 years of age, without evidence of coronary artery disease, structural heart disease, or significant arrhythmias. Four different QT-heart rate adjustment formulae were calculated and compared.
RESULTS: There were significant (P=0.0014) differences between the QT-heart rate relationship during three different time-periods (night 00:00 to 08:00 h, day 08:00 to 14:00 h and evening 14:00 to 24:00 h). Women, compared to men, had a steeper relation of QT to RR interval indicating that when heart rate slows at night, the QT interval is more prolonged which is consistent with a greater susceptibility to fatal arrhythmias. The variability of the QT interval (the SD) was significantly (P<0.01) greater in men than women at night and in the evening but not during the day. There were differences in the ability of different QT heart rate adjustment formulae to blunt the effect of heart rate changes on the QT interval during the day.
CONCLUSIONS: The time of the day that the QT interval is assessed should be considered. The QT heart rate relationship is different in women than in men especially at night. QT interval variability is greater at night especially in men. There are differences in the ability of QT heart rate adjustment formulae to blunt the effect of heart rate on the QT interval. Differences in the QTc at night might be the basis for the higher prevalence of sudden death in women at night.
摘要：
背景：测量ECG中的QT间期（QT间期）对于评估心脏死亡的风险和评估药物对心脏的影响很重要。这项研究的目的是确定一天中的时间是否影响QT间期，QT间期变异性以及这些关系是否受个体性别的影响。
方法：详细分析了50例个体的24小时心电图，49岁,没有冠状动脉疾病的证据，结构性心脏病,或严重的心律失常。计算并比较了四种不同的QT-心率调整公式。
结果：在三个不同时间段（夜间00:00至08:00h，天08:00至14:00h和晚上14:00至24:00h)。女人,和男人相比,QT与RR间期有更陡的关系，表明当夜间心率减慢时，QT间期延长，这与对致命性心律失常的易感性更高一致。男性在夜间和晚上的QT间期（SD）的变异性显着（P<0.01）大于女性，而在白天则没有。不同QT心率调整公式对白天心率变化对QT间期影响的能力存在差异。
结论：应考虑评估QT间期的当天时间。女性的QT心率关系与男性不同，尤其是在晚上。夜间QT间期变异性更大，尤其是男性。QT心率调整公式在削弱心率对QT间期影响的能力方面存在差异。夜间QTc的差异可能是女性夜间猝死患病率较高的基础。
方法：详细分析了50例个体的24小时心电图，49岁,没有冠状动脉疾病的证据，结构性心脏病,或严重的心律失常。计算并比较了四种不同的QT-心率调整公式。
结果：在三个不同时间段（夜间00:00至08:00h，天08:00至14:00h和晚上14:00至24:00h)。女人,和男人相比,QT与RR间期有更陡的关系，表明当夜间心率减慢时，QT间期延长，这与对致命性心律失常的易感性更高一致。男性在夜间和晚上的QT间期（SD）的变异性显着（P<0.01）大于女性，而在白天则没有。不同QT心率调整公式对白天心率变化对QT间期影响的能力存在差异。
结论：应考虑评估QT间期的当天时间。女性的QT心率关系与男性不同，尤其是在晚上。夜间QT间期变异性更大，尤其是男性。QT心率调整公式在削弱心率对QT间期影响的能力方面存在差异。夜间QTc的差异可能是女性夜间猝死患病率较高的基础。
