Ramírez Julia, Laguna Pablo, Bayés de Luna Antonio, Malik Marek, Pueyo Esther
Centro de Investigación Biomédica en Red (CIBER), Spain; Aragón Institute of Engineering Research, IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain.
Centro de Investigación Biomédica en Red (CIBER), Spain; Aragón Institute of Engineering Research, IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain.
J Electrocardiol. 2014 Nov-Dec;47(6):842-8. doi: 10.1016/j.jelectrocard.2014.08.013. Epub 2014 Aug 17.
Previous studies investigated the QT/RR relationship by linear regressions of QT and RR intervals. However, the pattern of the QT/RR relationship is not necessarily linear. This study investigated the QT/RR and T-peak-to-end (Tpe)/RR curvatures and corresponding slopes in chronic heart failure (CHF) patients, and studied their differences between sudden cardiac death (SCD) victims and others.
Holter ECG recordings of 650 CHF patients were analyzed. RR, QT and Tpe series were obtained and for each patient, the data of each subject were fitted with a non-linear regression function of the form: QT=χ+ϕ(1-RR(γ)), where γ is the QT/RR curvature. The same regression formula was applied to the Tpe interval series. The slopes (dimensionless units) were calculated at the averaged RR intervals and at RR of 1 second.
The median (difference between 75th and 25th percentile) of the curvature parameter was 0.226 (2.39) for QT/RR and -0.002 (3.64) for Tpe/RR in the overall sample. For the QT/RR slope, these values were 0.170 (0.12) and 0.190 (0.10) when evaluated at RR=1 and at the averaged RR, respectively, while for the Tpe/RR slope the values were 0.016 (0.04) and 0.020 (0.04), respectively. The Tpe/RR slope showed high statistical significance for separation of SCD victims and others, particularly when evaluated at the averaged RR (median values of 0.040 vs 0.020, p=0.002), but also when evaluated at RR=1 second (0.026 vs 0.015, p=0.023). Patients with values of Tpe/RR slope above 0.042 had double incidence of SCD, for the case of the slope being evaluated at RR=1 second, and triple incidence for the case of the slope being evaluated at the averaged RR. The QT/RR slope and curvature, as well as the Tpe/RR curvature, were not different in SCD victims and in others.
Non-linear regression models based on curvature and slope characteristics, individually obtained for each patient, were used to characterize the QT/RR and Tpe/RR relationships. Steeper Tpe/RR slopes, obtained after adjusting for the curvature parameter, were associated with higher incidence of SCD. The curvature parameter itself did not show SCD predictive value.
既往研究通过QT和RR间期的线性回归来研究QT/RR关系。然而，QT/RR关系的模式不一定是线性的。本研究调查了慢性心力衰竭（CHF）患者的QT/RR和T波峰末间期（Tpe）/RR曲线及其相应斜率，并研究了心源性猝死（SCD）患者与其他患者之间的差异。
分析了650例CHF患者的动态心电图记录。获取RR、QT和Tpe序列，对每位患者的数据用以下形式的非线性回归函数进行拟合：QT = χ + ϕ(1 - RR(γ))，其中γ是QT/RR曲线。将相同的回归公式应用于Tpe间期序列。在平均RR间期和RR为1秒时计算斜率（无量纲单位）。
在整个样本中，QT/RR曲线参数的中位数（第75百分位数与第25百分位数之差）为0.226（2.39），Tpe/RR曲线参数的中位数为 -0.002（3.64）。对于QT/RR斜率，在RR = 1时和平均RR时评估，这些值分别为0.170（0.12）和0.190（0.10），而对于Tpe/RR斜率，相应的值分别为0.016（0.04）和0.020（0.04）。Tpe/RR斜率在区分SCD患者与其他患者方面具有高度统计学意义，特别是在平均RR时评估（中位数分别为0.040和0.020，p = 0.002），在RR = 1秒时评估也具有统计学意义（0.026和0.015，p = 0.023）。当在RR = 1秒时评估斜率，Tpe/RR斜率值高于0.042的患者SCD发生率翻倍；当在平均RR时评估斜率，SCD发生率则为三倍。SCD患者与其他患者的QT/RR斜率和曲线，以及Tpe/RR曲线并无差异。
基于为每位患者单独获得的曲线和斜率特征的非线性回归模型，用于描述QT/RR和Tpe/RR关系。在调整曲线参数后获得的更陡的Tpe/RR斜率与更高的SCD发生率相关。曲线参数本身未显示出SCD预测价值。
