Neyroud N, Maison-Blanche P, Denjoy I, Chevret S, Donger C, Dausse E, Fayn J, Badilini F, Menhabi N, Schwartz K, Guicheney P, Coumel P
Lariboisière Hospital, Paris, France.
Eur Heart J. 1998 Jan;19(1):158-65. doi: 10.1053/euhj.1997.0730.
The long QT syndrome is mainly defined by QT interval prolongation (QTc > 0.44s). However, data obtained in genotyped patients showed that resting QTc measurement alone may be inaccurate for ascertaining the phenotype. The aim of this study was to evaluate the diagnostic performance of QT interval rate-dependence in untreated chromosome 11-linked patients.
The study population consisted of 25 untreated long QT patients linked to chromosome 11 and 25 age- and gender-matched controls. QTc intervals were measured on 12-lead resting ECG recordings. From 24-h Holter recordings, the slope of the relationship between ventricular repolarization and heart rate was studied separately day and night to assess neural modulation. Mean heart rates and rate-dependences of QT and Q-maximum of T (QTm) intervals were compared between long QT patients and controls for both time periods.
In both groups, the rate-dependences were modulated by day-night influences. When compared to controls, long QT patients showed a significant increase at night in QT/RR slopes (0.158 +/- 0.05 vs 0.117 +/- 0.03, P = 0.002) and QTm/RR slopes (0.163 +/- 0.05 vs 0.116 +/- 0.04, P = 0.0006). Multivariate analysis, adjusting QTc interval on age and gender, discriminated between long QT patients and controls with a 76% sensitivity and a 84% specificity. A 96% sensitivity and a 96% specificity were reached by taking into account the QTm/RR slope at night, the QTc interval and the mean heart rate during the day.
QT interval variables obtained from 24-h ECG recordings improve long QT syndrome diagnosis by showing an increased nocturnal ventricular repolarization rate-dependence in genotyped chromosome 11-linked patients.
长QT综合征主要由QT间期延长（QTc＞0.44秒）定义。然而，对基因分型患者的数据显示，仅测量静息QTc可能无法准确确定该表型。本研究的目的是评估未经治疗的11号染色体相关患者中QT间期频率依赖性的诊断效能。
研究人群包括25例未经治疗的与11号染色体相关的长QT患者和25例年龄及性别匹配的对照。在12导联静息心电图记录上测量QTc间期。从24小时动态心电图记录中，分别在白天和夜间研究心室复极与心率之间关系的斜率，以评估神经调节。比较长QT患者和对照在两个时间段的平均心率以及QT和T波最大间期（QTm）的频率依赖性。
在两组中，频率依赖性均受昼夜影响的调节。与对照相比，长QT患者夜间的QT/RR斜率（0.158±0.05对0.117±0.03，P = 0.002）和QTm/RR斜率（0.163±0.05对0.116±0.04，P = 0.0006）显著增加。在根据年龄和性别调整QTc间期的多变量分析中，区分长QT患者和对照的灵敏度为76%，特异度为84%。通过考虑夜间的QTm/RR斜率、QTc间期和白天的平均心率，灵敏度达到96%，特异度达到96%。
通过24小时心电图记录获得的QT间期变量显示，在基因分型的11号染色体相关患者中，夜间心室复极频率依赖性增加，从而改善了长QT综合征的诊断。
