Hekkala Anna-Mari, Väänänen Heikki, Swan Heikki, Oikarinen Lasse, Viitasalo Matti, Toivonen Lauri
Helsinki University Hospital, Department of Cardiology, Helsinki, Finland.
Ann Noninvasive Electrocardiol. 2006 Oct;11(4):318-26. doi: 10.1111/j.1542-474X.2006.00124.x.
Accurate measurement of the QT interval is important for diagnosing long QT syndrome (LQTS), and in research on determinants of ventricular repolarization time. We tested automatic analysis of QT intervals from multiple ECG leads on chest.
Eleven healthy volunteers and 10 genotyped LQTS patients were tested at rest and during exercise with a bicycle ergometer twice 1-31 months apart. Electrocardiograms were recorded with the body surface potential mapping system, and 12 precordial channels were selected for analysis. Averaged QT peak and QT end intervals were determined with an automated algorithm, and the difference QT end minus QT peak (Tp-e) was calculated. Repeatability was assessed by coefficient of variation (CV) between measurements.
Within one test at rest the QT end intervals were highly repeatable with CV 0.6%. In repeated tests CV was 4.4% for QT end interval and 3.5% when the QT interval was corrected for heart rate. In exercise test at specified heart rates, mean CV was 3.0% for QT end and 2.9% for QT peak interval. The CV of Tp-e interval was 10.2% at rest, and 9.3% in exercise test. Reproducibility was comparable between healthy subjects and LQTS patients.
The BSPM system with automated analysis produced accurate and highly repeatable QT interval measurements. Reproducibility was adequate also over prolonged time periods both at rest and in exercise stress test. The method can be applied in studying duration of ventricular repolarization time in different physiologic and pharmacologic interventions.
准确测量QT间期对于诊断长QT综合征（LQTS）以及心室复极时间决定因素的研究至关重要。我们测试了从胸部多个心电图导联自动分析QT间期。
11名健康志愿者和10名基因分型的LQTS患者在静息状态和使用自行车测力计进行运动时接受测试，两次测试间隔1 - 31个月。使用体表电位标测系统记录心电图，并选择12个胸前导联进行分析。采用自动算法确定平均QT峰间期和QT终末间期，并计算QT终末间期减去QT峰间期的差值（Tp - e）。通过测量之间的变异系数（CV）评估重复性。
在一次静息测试中，QT终末间期具有高度重复性，CV为0.6%。在重复测试中，QT终末间期的CV为4.4%，心率校正后的QT间期CV为3.5%。在指定心率的运动测试中，QT终末间期的平均CV为3.0%，QT峰间期为2.9%。Tp - e间期在静息时的CV为10.2%，运动测试中为9.3%。健康受试者和LQTS患者之间的可重复性相当。
具有自动分析功能的体表电位标测系统产生了准确且高度可重复的QT间期测量结果。在静息和运动应激测试中，长时间内的可重复性也足够。该方法可应用于研究不同生理和药物干预下心室复极时间的持续时间。
