Yeragani Vikram Kumar, Berger Ronald, Desai Nagaraj, Bar Karl Juergen, Chokka Pratap, Tancer Manuel
Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, MI, USA.
Ann Noninvasive Electrocardiol. 2007 Jul;12(3):203-9. doi: 10.1111/j.1542-474X.2007.00162.x.
Some studies suggest that it is important to take the end of "T" wave to quantify QT-interval variability, which signifies cardiac repolarization lability, as there is substantial and important information beyond the peak of the T wave on the surface electrocardiogram.
In this study, we examined the relationship between the variability of beat-to-beat RTe (beginning of R-peak to T-end) and the variability of RTp (R-peak to T-peak) in the following groups: normal controls (n = 26), patients with anxiety (n = 26), and patients with cardiovascular disease with or without diabetes (n = 63). We obtained ECG sampled at 1024 Hz in lead II configuration in supine posture to obtain beat-to-beat interbeat interval (R-R) and RT-interval variability for 256 seconds.
We found significant positive correlations (r = 0.8; P < 0.00001) in normal controls and patients with anxiety between the variability of RTeVI and RTpVI (RTe and RTp variability indices, respectively, corrected for the mean of RTe and RTp and the mean and the variance of R-R). These correlations were also statistically significant in the medically ill group but the r values were much smaller (r = 0.45 in various groups). The slopes were also significantly different between the two groups (P < 0.001). Bland-Altman plots also showed better agreement between the two measures in the controls and patients with anxiety compared to the group with cardiovascular disease.
These findings have methodological implications for studies comparing people with and without overt cardiovascular illness. While RTe or RTp variability index may be used interchangeably in normal controls and some patients with no overt cardiovascular problems, it may be more prudent to use both RTe and RTp variability indices in patients with cardiovascular illness. These indices, especially RTeVI, may provide different information about cardiac repolarization lability. Future studies should address the importance of the relative usefulness of these two measures especially in cardiac patients before and after successful treatment.
一些研究表明，以“T”波终点来量化QT间期变异性很重要，它代表心脏复极的易变性，因为体表心电图上T波峰值之外还有大量重要信息。
在本研究中，我们在以下几组中检查了逐搏RTe（R波峰起点至T波终点）变异性与RTp（R波峰至T波峰）变异性之间的关系：正常对照组（n = 26）、焦虑症患者（n = 26）以及患有或未患有糖尿病的心血管疾病患者（n = 63）。我们以仰卧姿势在II导联配置下以1024 Hz采样心电图，以获取256秒的逐搏心跳间期（R-R）和RT间期变异性。
我们发现，在正常对照组和焦虑症患者中，RTeVI（RTe变异性指数）和RTpVI（RTp变异性指数，分别针对RTe和RTp的均值以及R-R的均值和方差进行校正）之间存在显著正相关（r = 0.8；P < 0.00001）。这些相关性在患病组中也具有统计学意义，但r值要小得多（各亚组中r = 0.45）。两组之间的斜率也有显著差异（P < 0.001）。Bland-Altman图还显示，与心血管疾病组相比，对照组和焦虑症患者中这两种测量方法之间的一致性更好。
这些发现对比较有或无明显心血管疾病的人群的研究具有方法学意义。虽然RTe或RTp变异性指数在正常对照组和一些无明显心血管问题的患者中可以互换使用，但在心血管疾病患者中同时使用RTe和RTp变异性指数可能更为谨慎。这些指数，尤其是RTeVI，可能提供有关心脏复极易变性的不同信息。未来的研究应探讨这两种测量方法相对有用性的重要性，尤其是在心脏病患者成功治疗前后。
