Brouwer Jan, Van Den Berg Maarten P, Grobbee Diederick E, Haaksma Jaap, Wilde Arthur A M
Department of Cardiology, Thorax Center, University Hospital Groningen, Groningen, The Netherlands.
Ann Noninvasive Electrocardiol. 2003 Oct;8(4):269-74. doi: 10.1046/j.1542-474x.2003.08402.x.
Recently, we identified a novel mutation of SCN5A (1795insD) in a large family with LQTS3. The aim of this study was to assess whether the various proposed corrections of the QT interval to heart rate help to improve the identification of carriers of the mutant gene.
The study group consisted of 101 adult family members: 57 carriers and 44 noncarriers (mean age 44.6 +/- 14.6 and 40.3 +/- 12.8 years, respectively). In all individuals a 12-lead ECG, exercise ECG, and 24-hour Holter ECG were obtained.
Correction for heart rate significantly improved the diagnostic performance of the QT interval. Diagnostic performance of the Bazett formula was similar to that of the newer formulas (Fridericia, Hodges, Framingham, and a logarithmic formula). At a cut-off value of 440 ms, the Bazett corrected QT interval was associated with a sensitivity and specificity of 90% and 91%, respectively. Using the 24-hour Holter ECG, a prolonged QTc at heart rates less than 60 beats/min was almost pathognomonic for genetic mutation (sensitivity and specificity both 99%), whereas the QTc calculated at the lowest heart rate using Bazett's formula provided full discrimination.
In the present family, the resting ECG gave a good indication about the presence or absence of genetic mutation but a 24-hour Holter recording was mandatory to ascertain the diagnosis. In the diagnosis of this form of LQTS3, Bazett's formula was at least as good as other proposed corrections of the QT interval to heart rate.
最近，我们在一个患有长QT综合征3型（LQTS3）的大家庭中发现了SCN5A基因的一种新突变（1795insD）。本研究的目的是评估各种提议的心率校正QT间期方法是否有助于提高突变基因携带者的识别率。
研究组由101名成年家庭成员组成：57名携带者和44名非携带者（平均年龄分别为44.6±14.6岁和40.3±12.8岁）。所有个体均进行了12导联心电图、运动心电图和24小时动态心电图检查。
心率校正显著提高了QT间期的诊断性能。Bazett公式的诊断性能与较新的公式（Fridericia、Hodges、Framingham和对数公式）相似。在截断值为440毫秒时，Bazett校正QT间期的敏感性和特异性分别为90%和91%。使用24小时动态心电图，心率低于60次/分钟时QTc延长几乎对基因突变具有确诊意义（敏感性和特异性均为99%），而使用Bazett公式在最低心率时计算的QTc提供了完全的区分度。
在本家族中，静息心电图对基因突变的有无有很好的提示作用，但确诊必须进行24小时动态心电图记录。在诊断这种形式的LQTS3时，Bazett公式至少与其他提议的心率校正QT间期方法一样好。
