Department of Cardiovascular Medicine, Mayo Clinic; Phoenix, Arizona-United States.
Department of Cardiovascular Medicine, Smidt Heart Institute, Cedars Sinai Medical Center; Los Angeles, California-United States.
Anatol J Cardiol. 2021 Mar;25(3):170-176. doi: 10.14744/AnatolJCardiol.2020.10008.
Left bundle branch block (LBBB), which is associated with underlying cardiac disease, is believed to play a role in the pathogenesis of cardiomyopathy through delays in interventricular conduction, leading to dyssynchrony. However, this has not been established in previous studies. It is unclear whether LBBB indicates clinically advanced cardiac disease or is an independent factor responsible for increased mortality and the development of heart failure. We investigated the natural history of isolated LBBB without any associated structural heart disease in order to determine its clinical significance.
We performed a retrospective chart review on consecutive patients who fulfilled the 12-lead electrocardiographic (ECG) criteria for complete LBBB and had a normal echocardiogram with no evidence of structural heart disease and left or right ventricular systolic dysfunction within three months of the initial ECG between January 1, 2000 and December 31, 2009. We excluded patients with documented coronary artery disease (CAD) at any time, any structural heart disease, or cardiac devices. We evaluated the primary endpoints of mortality and incidence of cardiomyopathy, as well as any heart failure hospitalizations over a 1- and 10-year period.
We identified 2522 eligible patients. The mean follow-up duration was 8.4±3.2 years. The one-year mortality rate was 7.8%, with a 10-year mortality rate of 22.0%. The incidence of cardiomyopathy over one year was 3.2% and over 10 years was 9.1%. There was no significant difference in QRS duration between patients who were alive and those that were deceased at 10 years (141+/-18 vs. 141+/-17 ms; p=0.951) and patients with and without cardiomyopathy at 10 years (142±17 vs. 141±17 ms; p=0.532).
Isolated LBBB occurring without structural heart disease, ventricular dysfunction, or CAD is associated with a low mortality rate and incidence of cardiomyopathy.
左束支传导阻滞（LBBB）与潜在的心脏疾病有关，据信它通过延迟心室间传导导致不同步，在心肌病的发病机制中起作用。然而，这在以前的研究中尚未得到证实。目前尚不清楚 LBBB 是否表明存在临床晚期心脏疾病，还是导致死亡率增加和心力衰竭发展的独立因素。我们研究了孤立性 LBBB 而无任何相关结构性心脏病的自然病史，以确定其临床意义。
我们对 2000 年 1 月 1 日至 2009 年 12 月 31 日期间连续符合完全性 LBBB 12 导联心电图（ECG）标准且在初始 ECG 后三个月内无结构性心脏病和左或右心室收缩功能障碍证据的患者进行了回顾性图表审查。我们排除了任何时间有记录的冠心病（CAD）、任何结构性心脏病或心脏器械的患者。我们评估了 1 年和 10 年内死亡率和心肌病发生率以及任何心力衰竭住院的主要终点。
我们确定了 2522 名符合条件的患者。平均随访时间为 8.4±3.2 年。1 年死亡率为 7.8%，10 年死亡率为 22.0%。1 年内心肌病的发生率为 3.2%，10 年内为 9.1%。10 年内存活患者和死亡患者的 QRS 持续时间无显著差异（141+/-18 与 141+/-17 ms；p=0.951），以及有和无心肌病患者的 QRS 持续时间也无显著差异（142±17 与 141±17 ms；p=0.532）。
无结构性心脏病、心室功能障碍或 CAD 的孤立性 LBBB 与低死亡率和心肌病发生率相关。
