Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD 21218, USA.
Circ Arrhythm Electrophysiol. 2011 Dec;4(6):858-66. doi: 10.1161/CIRCEP.110.961763. Epub 2011 Aug 14.
Instability in ventricular repolarization in the presence of premature activations (PA) plays an important role in arrhythmogenesis. However, such instability cannot be detected clinically. This study developed a methodology for detecting QT interval (QTI) dynamics instability from the ECG and explored the contribution of PA and QTI instability to ventricular tachycardia (VT) onset.
To examine the contribution of PAs and QTI instability to VT onset, ECGs of 24 patients with acute myocardial infarction, 12 of whom had sustained VT (VT) and 12 nonsustained VT (NSVT), were used. From each patient ECG, 2 10-minute-long ECG recordings were extracted, 1 right before VT onset (onset epoch) and 1 at least 1 hour before it (control epoch). To ascertain how PA affects QTI dynamics stability, pseudo-ECGs were calculated from an MRI-based human ventricular model. Clinical and pseudo-ECGs were subdivided into 1-minute recordings (minECGs). QTI dynamics stability of each minECG was assessed with a novel approach. Frequency of PAs (f(PA)) and the number of minECGs with unstable QTI dynamics (N(us)) were determined for each patient. In the VT group, f(PA) and N(us) of the onset epoch were larger than in control. Positive regression relationships between f(PA) and N(us) were identified in both groups. The simulations showed that both f(PA) and the PA degree of prematurity contribute to QTI dynamics instability.
Increased PA frequency and QTI dynamics instability precede VT onset in patients with acute myocardial infarction, as determined by novel methodology for detecting instability in QTI dynamics from clinical ECGs.
过早激活（PA）存在时心室复极的不稳定性在心律失常发生中起着重要作用。然而，这种不稳定性在临床上无法检测到。本研究开发了一种从心电图检测 QT 间期（QTI）动力学不稳定性的方法，并探讨了 PA 和 QTI 不稳定性对室性心动过速（VT）发作的贡献。
为了研究 PA 和 QTI 不稳定性对 VT 发作的贡献，使用了 24 例急性心肌梗死患者的心电图，其中 12 例发生持续性 VT（VT），12 例发生非持续性 VT（NSVT）。从每位患者的心电图中提取了 2 段 10 分钟长的心电图记录，1 段在 VT 发作前（发作期），1 段至少在发作前 1 小时（对照期）。为了确定 PA 如何影响 QTI 动力学稳定性，从基于 MRI 的人心室模型计算了伪心电图。将临床和伪心电图分为 1 分钟记录（minECG）。使用一种新方法评估每个 minECG 的 QTI 动力学稳定性。确定了每位患者的 PA 频率（f（PA））和不稳定 QTI 动力学的 minECG 数量（N（us））。在 VT 组中，发作期的 f（PA）和 N（us）大于对照期。在两组中均发现了 f（PA）和 PA 提前程度与 N（us）之间的正回归关系。模拟结果表明，PA 频率和 PA 提前程度都导致了 QTI 动力学不稳定性。
通过检测临床 ECG 中 QTI 动力学不稳定性的新方法，在急性心肌梗死患者中，PA 频率增加和 QTI 动力学不稳定性先于 VT 发作。
