Key result
QRS ≥160 ms in LBBB linked to ~3.5-fold higher rate of LV systolic dysfunction.
Why the study?
The relationship between QRS duration in LBBB and left ventricular systolic function was unclear and needed evaluation by echocardiography.
Does a QRS duration ≥160 ms associate with left ventricular systolic dysfunction in patients with LBBB?
Cross-Sectional (n=82)
Does a QRS duration ≥160 ms associate with left ventricular systolic dysfunction in patients with LBBB?
Absolute Event Rate: 70.4% vs 20%
p-value: p=<0.001
Prolongation of QRS duration to ≥160 ms in patients with LBBB is a marker of significant left ventricular systolic dysfunction.
QRS ≥160 ms marks higher LV dysfunction odds in LBBB; leaves open whether it refines risk stratification in prospective cohorts.
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.
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Zebari et al. (2019) conducted a cross-sectional in Left bundle branch block (n=82). QRS duration ≥160 ms vs. QRS duration <160 ms was evaluated on Left ventricular systolic dysfunction (ejection fraction <40%) (p=<0.001). QRS duration ≥160 ms in left bundle branch block was associated with a higher incidence of left ventricular systolic dysfunction compared to QRS <160 ms (70.4% vs 20%; P<0.001).
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