The prevalence and association of patients with impaired left ventricular ejection fraction and complete left bundle-branch block in Taiwan.

BACKGROUND/PURPOSE: A deleterious effect of complete left bundle-branch block (cLBBB) on left ventricular (LV) function has been established. The underutilization of cardiac resynchronization therapy has been noted in Taiwan and the Asian-Pacific area, but the reasons remain unclear. This study aimed to evaluate the prevalence and association of cLBBB and impaired LV ejection fraction (LVEF) in patients at the National Taiwan University Hospital (NTUH).

METHODS: We enrolled 164,049 patients who underwent standard 12-lead electrocardiography (ECG) between January 2010 and December 2013 at NTUH. Echocardiographic examinations within one year of the index ECG were analyzed. Baseline clinical characteristics, electrocardiography and ECG parameters, in patients with cLBBB were compared among those with three different LVEFs (EF <35%, 35%≤ EF<50%, and EF ≥50%). Multivariable logistic regression analysis were conducted to identify independent predictors of impaired LVEF in patient with cLBBB.

RESULTS: The prevalence of cLBBB was 0.4% (648 patients), and it increased with age. The estimated prevalence of cLBBB and LVEF <35% was about 0.1%. The effects of age on the distributions of patients with cLBBB by three different EF statuses were significantly disparate. In patients with cLBBB aged >80 years, 64% had a normal EF. However, in those aged between 40 and 60 years, the risk of EF <35% was as high as 45%, and the risk of EF <50% was even higher at 60%.

CONCLUSIONS: Patients in Taiwan had a low prevalence of LVEF<35% and cLBBB. About three-fourth of patients with cLBBB did not experience HF events, and 56% of them had a normal LVEF. The development of an effective triage strategy for these patients is warranted.