Division of Cardiology, Department of Medicine, Duke University, Durham, North Carolina.
Duke Clinical Research Institute, Duke University, Durham, North Carolina.
J Am Coll Cardiol. 2018 Jan 23;71(3):306-317. doi: 10.1016/j.jacc.2017.11.020.
Patients with left bundle branch block (LBBB) often respond to cardiac resynchronization therapy (CRT) with left ventricular ejection fraction (LVEF) improvement. Guideline-directed medical therapy (GDMT), not CRT, is first-line therapy for patients with reduced LVEF with LBBB. However, there are little data on how patients with reduced LVEF and LBBB respond to GDMT.
This study examined patients with cardiomyopathy and sought to assess rates of LVEF improvement for patients with LBBB compared to other QRS morphologies.
Using data from the Duke Echocardiography Laboratory Database, the study identified patients with baseline electrocardiography and LVEF ≤35% who had a follow-up LVEF 3 to 6 months later. The study excluded patients with severe valve disease, a cardiac device, left ventricular assist device, or heart transplant. QRS morphology was classified as LBBB, QRS duration <120 ms (narrow QRS duration), or a wide QRS duration ≥120 ms but not LBBB. Analysis of variance testing compared mean change in LVEF among the 3 groups with adjustment for significant comorbidities and GDMT.
There were 659 patients that met the criteria: 111 LBBB (17%), 59 wide QRS duration ≥120 ms but not LBBB (9%), and 489 narrow QRS duration (74%). Adjusted mean increase in LVEF over 3 to 6 months in the 3 groups was 2.03%, 5.28%, and 8.00%, respectively (p < 0.0001). Results were similar when adjusted for interim revascularization and myocardial infarction. Comparison of mean LVEF improvement between patients with LBBB on GDMT and those not on GDMT showed virtually no difference (3.50% vs. 3.44%). The combined endpoint of heart failure hospitalization or mortality was highest for patients with LBBB.
LBBB is associated with a smaller degree of LVEF improvement compared with other QRS morphologies, even with GDMT. Some patients with LBBB may benefit from CRT earlier than guidelines currently recommend.
左束支传导阻滞（LBBB）患者的左心室射血分数（LVEF）通常会因心脏再同步治疗（CRT）而改善。对于 LVEF 降低伴 LBBB 的患者，指南指导的药物治疗（GDMT）而非 CRT 是一线治疗方法。然而，对于 LVEF 降低伴 LBBB 的患者对 GDMT 的反应，数据很少。
本研究检查了心肌病患者，并评估了 LBBB 患者与其他 QRS 形态相比 LVEF 改善的发生率。
利用杜克超声心动图实验室数据库的数据，研究确定了基线心电图和 LVEF≤35%且随访 LVEF 为 3 至 6 个月的患者。研究排除了严重瓣膜疾病、心脏装置、左心室辅助装置或心脏移植的患者。QRS 形态分为 LBBB、QRS 时限<120ms（窄 QRS 时限）或宽 QRS 时限≥120ms 但非 LBBB。采用方差分析比较 3 组间 LVEF 的平均变化，并对有意义的合并症和 GDMT 进行调整。
共有 659 名患者符合标准：111 名 LBBB（17%）、59 名宽 QRS 时限≥120ms 但非 LBBB（9%）和 489 名窄 QRS 时限（74%）。3 组间 3 至 6 个月的 LVEF 平均增加值分别为 2.03%、5.28%和 8.00%（p<0.0001）。当调整中期血运重建和心肌梗死的因素时，结果相似。在 GDMT 治疗和未接受 GDMT 治疗的 LBBB 患者之间，平均 LVEF 改善的比较几乎没有差异（3.50%对 3.44%）。LBBB 患者心力衰竭住院或死亡率的联合终点最高。
与其他 QRS 形态相比，LBBB 与较小程度的 LVEF 改善相关，即使接受 GDMT 治疗也是如此。一些 LBBB 患者可能比指南目前建议的更早受益于 CRT。
