The association of duration of QRS complex in left bundle branch block with left ventricular systolic function

Abstract EN

Background: Left bundle branch block (LBBB) indicates organic heart disease.

It is responsible for a greater degree of asynchrony in the left ventricular (LV) contraction as a result of alteration in LV depolarization sequence.

This study aimed to compare the duration of QRS complex in LBBB in relation to LV systolic function by two‑dimensional transthoracic echocardiography.

Patients and Methods: In this cross‑sectional study, 82 patients with LBBB were divided into two groups.

Group I defined as QRS <160 ms and Group II defined as QRS ≥160 ms.

Then, the relationships between QRS duration and echocardiographic LV ejection fraction (EF) were derived.

LV systolic dysfunction defined as EF <40%.

Results: Eighty‑two patients with (LBBB) had been included in the study, the duration of the QRS complex of 55 patients (67%) was <160 ms (Group I), and it was ≥160 ms (Group II) in 27 patients (33%).

More than half (55.6%) of Group II aged ≥70 years compared with 38.2% of Group I (P = 0.001).

Group II had high incidence of LV systolic dysfunction (70.4%) compared with 20% in Group I, while 18.2% of Group I had an EF of ≥60% compared with 3.7% in Group II (P < 0.001).

Conclusion: The prolongation of QRS duration (≥160 ms) in LBBB is a marker of significant LV systolic dysfunction.