University of California-San Diego and Veterans Affairs Medical Center, San Diego, CA.
Circ Arrhythm Electrophysiol. 2013 Oct;6(5):859-67. doi: 10.1161/CIRCEP.113.000204. Epub 2013 Aug 31.
Few clinical indices identify the propensity of patients to atrial fibrillation (AF) when not in AF. Repolarization alternans has been shown to indicate AF vulnerability, but is limited in its sensitivity to detect changes in action potential (AP) duration (APD), which may be subtle. We hypothesized that spectral analysis would be a more sensitive and robust marker of AP alternans and thus a better clinical index of individual propensity to AF than APD alternans.
In 31 patients (12 persistent AF, 15 paroxysmal AF, 4 controls with no AF), we recorded left (n=27) and right (n=6) atrial monophasic APs during incremental pacing from cycle length 500 ms (120 beats per minute) to AF onset. Alternans was measured by APD and spectral analysis. At baseline pacing (median cycle length [1st, 3rd quartiles], 500 ms [500, 500]), APD alternans was detected in only 7 of 27 AF patients (no controls), whereas spectral AP alternans was detected in 18 of 27 AF patients (no controls; P=0.003); AP alternans was more prevalent in persistent than paroxysmal AF, and absent in controls (P=0.018 APD; P=0.042 spectral). Spectral AP alternans magnitude at baseline was highest in persistent AF, with modest rate-dependent amplification, followed by paroxysmal AF, with marked rate dependence, and undetectable in controls until just before induced AF.
Spectral AP alternans near baseline rates can identify patients with, versus those without, clinical histories and pathophysiological substrates for AF. Future studies should examine whether the presence of spectral AP alternans during sinus rhythm may obviate the need to actually demonstrate AF, such as on ambulatory ECG monitoring.
在非房颤（AF）状态下，很少有临床指标能够确定患者发生房颤的倾向。复极交替已经被证明可以指示房颤易感性，但在检测动作电位（AP）持续时间（APD）变化方面的敏感性有限，这些变化可能很细微。我们假设，频谱分析将是 AP 交替的更敏感和更稳健的标志物，因此是个体发生房颤倾向的比 APD 交替更好的临床指标。
在 31 名患者（12 名持续性房颤、15 名阵发性房颤、4 名无房颤的对照）中，我们在从周长 500 毫秒（120 次/分钟）递增起搏至房颤发作期间记录了左（n=27）和右（n=6）心房单相动作电位。通过 APD 和频谱分析测量交替。在基线起搏（中位数周长[第 1 四分位数，第 3 四分位数]，500 毫秒[500，500]）时，仅在 27 名 AF 患者中的 7 名（无对照）中检测到 APD 交替，而在 27 名 AF 患者中的 18 名（无对照）中检测到频谱 AP 交替（P=0.003）；持续性房颤中的 AP 交替比阵发性房颤更常见，对照组中不存在（APD 时 P=0.018；频谱时 P=0.042）。基线时，持续性房颤的频谱 AP 交替幅度最高，呈适度的频率依赖性放大，其次是阵发性房颤，具有明显的频率依赖性，而在对照组中，直到诱发房颤前才检测到。
在接近基础率时，频谱 AP 交替可以识别有临床病史和房颤病理生理学基础的患者与无这些病史和基础的患者。未来的研究应该检查在窦性节律期间是否存在频谱 AP 交替可以避免实际显示房颤的需要，例如在动态心电图监测中。
