BackgroundUnlike T‐wave alternans (TWA), the relation between QRS alternans (QRSA) and ventricular arrhythmia (VA) risk has not been evaluated in hypertrophic cardiomyopathy (HCM). We assessed microvolt QRSA/TWA in relation to HCM risk factors and late VA outcomes in HCM.Methods and ResultsProspectively enrolled patients with HCM (n=130) with prophylactic implantable cardioverter‐defibrillators underwent digital 12‐lead ECG recordings during ventricular pacing (100–120 beats/min). QRSA/TWA was quantified using the spectral method. Patients were categorized as QRSA+ and/or TWA+ if sustained alternans was present in ≥2 precordial leads. The VA end point was appropriate implantable cardioverter‐defibrillator therapy over 5 years of follow‐up. QRSA+ and TWA+ occurred together in 28% of patients and alone in 7% and 7% of patients, respectively. QRSA magnitude increased with pacing rate (1.9±0.6 versus 6.2±2.0 µV; P=0.006). Left ventricular thickness was greater in QRSA+ than in QRSA− patients (22±7 versus 20±6 mm; P=0.035). Over 5 years follow‐up, 17% of patients had VA. The annual VA rate was greater in QRSA+ versus QRSA− patients (5.8% versus 2.0%; P=0.006), with the QRSA+/TWA− subgroup having the greatest rate (13.3% versus 2.6%; P<0.001). In those with <2 risk factors, QRSA− patients had a low annual VA rate compared QRSA+ patients (0.58% versus 7.1%; P=0.001). Separate Cox models revealed QRSA+ (hazard ratio [HR], 2.9 [95% CI, 1.2–7.0]; P=0.019) and QRSA+/TWA− (HR, 7.9 [95% CI, 2.9–21.7]; P<0.001) as the most significant VA predictors. TWA and HCM risk factors did not predict VA.ConclusionsIn HCM, microvolt QRSA is a novel, rate‐dependent phenomenon that can exist without TWA and is associated with greater left ventricular thickness. QRSA increases VA risk 3‐fold in all patients, whereas the absence of QRSA confers low VA risk in patients with <2 risk factors.RegistrationURL: https://www.clinicaltrials.gov; Unique identifier: NCT02560844.

中文翻译：

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肥厚型心肌病中的微伏 QRS 交替信号：晚期室性心律失常的新风险标志物

背景与 T 波交替 (TWA) 不同，QRS 交替 (QRSA) 与室性心律失常 (VA) 风险之间的关系尚未在肥厚型心肌病 (HCM) 中进行评估。我们评估了微伏 QRSA/TWA 与 HCM 危险因素和 HCM 晚期 VA 结局的关系。方法和结果 前瞻性招募的 HCM 患者（n=130）使用预防性植入式心脏复律除颤器在心室起搏期间接受了数字 12 导联心电图记录（100- 120 次/分钟）。QRSA/TWA 使用光谱法进行量化。如果≥2 个心前导联存在持续交替信号，则患者被归类为 QRSA+ 和/或 TWA+。VA 终点是经过 5 年随访的适当植入式心脏复律除颤器治疗。QRSA+ 和 TWA+ 同时出现在 28% 的患者中，单独出现在 7% 和 7% 的患者中。P = 0.006）。QRSA+ 患者的左心室厚度大于 QRSA− 患者（22±7 对 20±6 mm；P = 0.035）。超过 5 年的随访，17% 的患者有 VA。QRSA+ 与 QRSA− 患者的年 VA 发生率更高（5.8% 与 2.0%；P = 0.006），QRSA+/TWA− 亚组的发生率最高（13.3% 与 2.6%；P <0.001）。在具有<2 个风险因素的患者中，与 QRSA+ 患者相比，QRSA− 患者的年 VA 发生率较低（0.58% 对 7.1%；P = 0.001）。单独的 Cox 模型显示 QRSA+（风险比 [HR]，2.9 [95% CI，1.2-7.0]；P = 0.019）和 QRSA+/TWA-（HR，7.9 [95% CI，2.9-21.7]；P<0.001) 作为最重要的 VA 预测因子。TWA 和 HCM 危险因素不能预测 VA。结论在 HCM 中，微伏 QRSA 是一种新的、速率依赖的现象，在没有 TWA 的情况下也可以存在，并且与更大的左心室厚度相关。QRSA 使所有患者的 VA 风险增加 3 倍，而没有 QRSA 的患者具有 <2 个风险因素的 VA 风险较低。RegistrationURL：https://www.clinicaltrials.gov；唯一标识符：NCT02560844。