Narayan Sanjiv M, Franz Michael R, Lalani Gautam, Kim Jason, Sastry Ashwani
University of California and Veterans Affairs Medical Center, San Diego, California 92161, USA.
J Am Coll Cardiol. 2007 Dec 18;50(25):2385-92. doi: 10.1016/j.jacc.2007.10.011.
Our aim was to study the relationship between T-wave alternans (TWA) and rate-response (restitution) of repolarization in subjects with and without ventricular systolic dysfunction.
T-wave alternans is a promising predictor of sudden death, yet the mechanisms linking it with human ventricular arrhythmias are unclear. From theoretic considerations, we hypothesized that abnormal TWA is linked with steep restitution of action potential duration (APD) and that both predict arrhythmic outcome.
We studied 53 subjects with left ventricular ejection fraction (LVEF) < or =40% and 18 control subjects. At electrophysiologic study, we recorded APD at 90% repolarization (APD(90)) in the right (n = 62) or left (n = 9) ventricle during pacing while measuring TWA from the body surface.
As expected, TWA (at <109 beats/min) was more likely to be abnormal in study than in control subjects (p < 0.01). However, study (LVEF 28 +/- 8%) and control (LVEF 58 +/- 12%) subjects did not differ in APD(90) restitution slope maxima (1.2 +/- 0.6 vs. 1.3 +/- 0.6, respectively; p = 0.82) or numbers with steep slope (>1; 58% vs. 67%). T-wave alternans and simultaneous APD alternans always occurred at diastolic intervals where APD restitution was not steep (p < 0.001), and there was no relationship between maximum restitution slope and TWA magnitude. Over 829 +/- 473 days, TWA (p = 0.02), but not restitution slope >1, predicted ventricular arrhythmias in subjects with LVEF < or =40%.
The mechanism by which TWA predicts arrhythmic mortality does not reflect the maximum slope of ventricular APD restitution. Better understanding of the mechanisms underlying TWA may enable improved prediction and prevention of ventricular arrhythmias.
我们的目的是研究有和没有心室收缩功能障碍的受试者中T波交替（TWA）与复极化的频率反应（恢复）之间的关系。
T波交替是猝死的一个有前景的预测指标，但其与人类室性心律失常相关的机制尚不清楚。从理论考虑，我们假设异常TWA与动作电位时程（APD）的陡峭恢复相关，且两者都可预测心律失常结局。
我们研究了53例左心室射血分数（LVEF）≤40%的受试者和18例对照受试者。在电生理研究中，我们在起搏期间记录右心室（n = 62）或左心室（n = 9）复极化90%时的APD（APD(90)），同时从体表测量TWA。
正如预期的那样，研究组受试者中TWA（心率<109次/分钟时）比对照组更易异常（p < 0.01）。然而，研究组（LVEF 28±8%）和对照组（LVEF 58±12%）受试者在APD(90)恢复斜率最大值方面无差异（分别为1.2±0.6与1.3±0.6；p = 0.82），斜率陡峭（>1）的人数也无差异（58%对67%）。T波交替和同时出现的APD交替总是发生在APD恢复不陡峭的舒张期（p < 0.001），且最大恢复斜率与TWA幅度之间无关联。在829±473天期间，TWA（p = 0.02）而非恢复斜率>1可预测LVEF≤40%的受试者发生室性心律失常。
TWA预测心律失常死亡的机制并不反映心室APD恢复的最大斜率。更好地理解TWA背后的机制可能有助于改善室性心律失常的预测和预防。
