Department of Electrical and Computer Engineering, Ryerson University, Toronto, Canada.
Department of Computer and Electrical Engineering, Florida Atlantic University, Boca Raton, Florida, United States of America.
PLoS One. 2019 Apr 10;14(4):e0214729. doi: 10.1371/journal.pone.0214729. eCollection 2019.
T wave alternans (TWA) is an electrocardiographic marker of heightened sudden death risk from ventricular tachyarrhythmias in patients with cardiomyopathy. TWA is evaluated from the 12-lead electrocardiogram, Frank lead, or Holter lead recordings, however these clinical lead configurations will not record TWA from adjacent regions of the body torso.
We tested the hypothesis that changing heart rate or ventricular activation may alter the body surface distribution of TWA such that the clinical ECG leads fail to detect TWA in some patients; thereby producing a false-negative test.
In 28 cardiomyopathy patients (left ventricular ejection fraction 28±6%), 114 unipolar electrograms were recorded across the body torso during incremental atrial pacing, followed by atrioventricular pacing at 100, 110 and 120bpm. TWA was measured from each unipolar electrogram using the spectral method. A clinically positive TWA test was defined as TWA magnitude (Valt) ≥1.9 uV with k ≥3 at ≤110bpm.
Maximum Valt (TWAmax) was greater from the body torso than clinical leads during atrial (p<0.005) and atrioventricular pacing (p<0.005). TWAmax was most prevalent in the right lower chest with atrial pacing 100 bpm and shifted to the left lower chest at 120 bpm. TWAmax was most prevalent in left lower chest with atrioventricular pacing at 100 bpm and shifted to the left upper chest at 120 bpm. Using the body torso as a gold standard, the false-negative rate for clinically positive TWA with clinical leads was 21% during atrial and 11% during atrioventricular pacing. Due to TWA signal migration outside the clinical leads, clinically positive TWA became false-negative when pacing mode was switched (atrial→atrioventricular pacing) in 21% of patients.
The body surface distribution of TWA is modulated by heart rate and the sequence of ventricular activation in patients with cardiomyopathy, which can give rise to modest false-negative TWA signal detection using standard clinical leads.
T 波交替（TWA）是一种心电图标志，表明心肌病患者室性心动过速和心律失常的猝死风险增加。TWA 可从 12 导联心电图、Frank 导联或动态心电图记录中进行评估，但是这些临床导联配置无法记录身体躯干相邻区域的 TWA。
我们检验了如下假说，即心率或心室激动的变化可能改变 TWA 的体表分布，从而导致某些患者的临床心电图导联无法检测到 TWA，即出现假阴性检测结果。
在 28 例心肌病患者（左心室射血分数 28±6%）中，在递增性心房起搏过程中记录了 114 个体表单极电图，随后进行房室起搏，起搏频率分别为 100、110 和 120 次/分。使用频谱法从每个单极电图中测量 TWA。临床阳性 TWA 试验定义为 TWA 幅度（Valt）≥1.9uV，k≥3，且起搏频率≤110 次/分。
心房起搏（p<0.005）和房室起搏（p<0.005）时，TWA 的最大幅度（TWAmax）从身体躯干记录的导联大于临床导联。TWAmax 在心房起搏 100 次/分时最常见于右胸下部，在 120 次/分时转移至左胸下部。在房室起搏 100 次/分时，TWAmax 最常见于左胸下部，在 120 次/分时转移至左胸上部。以身体躯干为金标准，在心房起搏和房室起搏时，临床阳性 TWA 的假阴性率分别为 21%和 11%。由于 TWA 信号在临床导联外迁移，当起搏模式从心房起搏切换为房室起搏时（21%的患者），临床阳性 TWA 变为假阴性。
在心肌病患者中，TWA 的体表分布受心率和心室激动顺序的调节，这可能导致使用标准临床导联时对 TWA 信号的检测出现适度假阴性。
