Division of Cardiovascular Diseases, Department of Internal Medicine, University of Iowa College of Medicine and Veterans Administration Medical Center, Iowa City, USA.
Transl Res. 2011 Nov;158(5):265-72. doi: 10.1016/j.trsl.2011.07.001. Epub 2011 Aug 3.
T-wave alternans (TWA) has been investigated as a marker for susceptibility to lethal ventricular arrhythmia. In this article, we studied intracardiac TWA and ischemia as predictors of spontaneous ventricular tachycardia (VT) or ventricular fibrillation (VF) in a canine model of coronary artery occlusion (CAO). Anesthetized, open-chest dogs were studied. Electrograms from intracardiac bipolar electrodes (IBEs) were assessed for TWA and spontaneous VT or VF. TWA was defined on IBE as T wave voltage change on every other complex. In each heart, we examined 62 electrograms measured in the risk zone and surrounding normal sites, filtered from 3 to 1300 Hz. Ischemia was measured as percent of all IBE recorded that had QRS voltage drop >45%. Mapping localized the three-dimensional origin of spontaneous VT or VF. The data from dogs with VF (n = 5), VT (n = 8), or controls (no VT or VF, n = 8) were analyzed before left CAO, at the 20th min after CAO and times immediately preceding VT and VF. We found a correlation between intracardiac TWA and ischemia. More importantly, increases in intracardiac TWA peaked immediately preceding spontaneous VF and VT and were significantly higher compared to controls at comparable times. At VT/VF origins and adjacent sites, the mean TWA magnitude and discordance of TWA distinguished between VT/VF and controls at comparable times but not between VT and VF or between reentry and focal mechanisms. TWA was more common than ischemia at VT/VF origins. In summary, changes in intracardiac TWA and ischemia correlate with impending spontaneous VT/VF in a clinically applicable canine model of CAO.
T 波电交替（TWA）已被研究作为预测致命性室性心律失常易感性的标志物。本文研究了心内 TWA 和缺血作为冠状动脉闭塞（CAO）犬模型中自发性室性心动过速（VT）或心室颤动（VF）的预测指标。研究对象为麻醉开胸犬。评估心内双极电极（IBEs）的心电图以确定 TWA 和自发性 VT 或 VF。在 IBE 上，TWA 定义为每两个复合波的 T 波电压变化。在每个心脏中，我们检查了在风险区和周围正常部位测量的 62 个电描记图，滤波范围为 3 至 1300 Hz。缺血的测量方法是记录的所有 IBE 中 QRS 电压下降>45%的百分比。映射定位了自发性 VT 或 VF 的三维起源。对 VT（n = 8）、VF（n = 5）或对照组（无 VT 或 VF，n = 8）的犬进行左 CAO 前、CAO 后 20 分钟以及 VT 和 VF 发生前的时间点的数据分析。我们发现心内 TWA 与缺血之间存在相关性。更重要的是，心内 TWA 的增加在自发性 VF 和 VT 发生前即刻达到峰值，并且在可比时间点明显高于对照组。在 VT/VF 起源和相邻部位，TWA 幅度和 TWA 不协调性的平均值可在可比时间点区分 VT/VF 和对照组，但不能区分 VT 和 VF 或折返和局灶性机制。在 VT/VF 起源处，TWA 比缺血更常见。总之，在临床适用的 CAO 犬模型中，心内 TWA 和缺血的变化与即将发生的自发性 VT/VF 相关。
