Steinbigler P, Haberl R, Nespithal K, Spiegl A, Schmücking I, Steinbeck G
Medical Hospital 1, University of Munich, Germany.
J Electrocardiol. 1998;30 Suppl:137-44. doi: 10.1016/s0022-0736(98)80061-7.
Inhomogeneous repolarization is considered to be associated with increased risk of ventricular arrhythmias, but exact determination of the end of the T wave is difficult, and a single measurement of the QTc interval may be insufficient for risk stratification. A new algorithm was therefore developed to determine the beat-to-beat variability of the T wave in Holter electrocardiographic recordings. This algorithm, termed T Wave Spectral Variance (TWSV) uses the two-dimensional fast Fourier transform to determine the beat-to-beat variability of the T wave in Hotter ECG recordings. The two-dimensional fast Fourier transform was calculated by use of a data matrix with 1,024 consecutive single beats (first dimension) and a 200-ms segment centered on the T wave (second dimension). The power spectra of the 2D-FFT revealed the frequency content of the T wave in the first dimension and the periodicity of these frequencies in cycles per beat in the second dimension. A TWSV index of periodicity was calculated by dividing total spectral energy by spectral energy at 0 cycles per beat. A TWSV index of 0 means a constant T wave from beat to beat; a TWSV index of 1 means a completely irregular T wave. Of the 200 patients investigated, all of whom had had myocardial infarctions, 50 had documented sustained ventricular tachycardia (VT) (<230 beats/min) (group 1), 50 had ventricular fibrillation (VF) (group 2), and 100 were without VT or VF (group 3); 10 normal subjects were also investigated. The visually determined QTc was 442 +/- 62 ms in group 1, 402 +/- 13 ms in group 2, 411 +/- 26 ms in group 3, and 398 +/- 43 ms in normal subjects (differences not significant). The TWSV index was 0.95 +/- 0.14 in group 1, 0.90 +/- 0.16 in group 2, and 0.64 +/- 0.24 in group 3; it showed a highly constant T wave in normal subjects (0.52 +/- 0.23). Differences between patients with VT and VF as against patients without VT or VF were significant (P < .05), whereas no statistical differences between patients with VT and VF could be found. Thus, TWSV, a new method to assess beat-to-beat variability of the T wave, revealed increased heterogeneity of repolarization in patients prone to both VT and VF after myocardial infarction, whereas a single QTc interval measurement showed no significant differences.
复极不均一性被认为与室性心律失常风险增加相关，但准确确定T波终点较为困难，单次测量QTc间期可能不足以进行风险分层。因此，开发了一种新算法来确定动态心电图记录中T波的逐搏变异性。该算法称为T波频谱方差（TWSV），它使用二维快速傅里叶变换来确定动态心电图记录中T波的逐搏变异性。二维快速傅里叶变换是通过使用一个数据矩阵来计算的，该数据矩阵包含1024个连续的单个心搏（第一维度）以及以T波为中心的200毫秒时间段（第二维度）。二维快速傅里叶变换的功率谱在第一维度上揭示了T波的频率成分，在第二维度上揭示了这些频率的每搏周期的周期性。通过将总频谱能量除以每搏0周期时的频谱能量来计算周期性的TWSV指数。TWSV指数为0表示T波逐搏恒定；TWSV指数为1表示T波完全不规则。在接受调查的200例患者中，所有患者均有心肌梗死病史，其中50例有记录的持续性室性心动过速（VT）（<230次/分钟）（第1组），50例有室颤（VF）（第2组），100例无VT或VF（第3组）；还对10名正常受试者进行了调查。第1组目测的QTc为442±62毫秒，第2组为402±13毫秒，第3组为411±26毫秒，正常受试者为398±43毫秒（差异无统计学意义）。第1组的TWSV指数为0.95±0.14，第2组为0.90±0.16，第3组为0.64±0.24；正常受试者显示T波高度恒定（0.52±0.23）。有VT和VF的患者与无VT或VF的患者之间的差异具有统计学意义（P<.05），而有VT和VF的患者之间未发现统计学差异。因此，TWSV作为一种评估T波逐搏变异性的新方法，揭示了心肌梗死后易发生VT和VF的患者复极不均一性增加，而单次QTc间期测量未显示出显著差异。
