From the Guidelines
Left bundle (LB) branch dysynchrony and abnormal septal bounce on echocardiogram (echo) indicate left ventricular systolic dysfunction and underlying structural heart disease.
Key Findings
- The presence of left bundle branch block (LBBB) on electrocardiogram (ECG) markedly increases the likelihood of underlying structural heart disease and left ventricular systolic dysfunction 1.
- Echocardiography is usually the most appropriate initial screening test for structural heart disease, including left ventricular systolic dysfunction 1.
- LB branch dysynchrony and abnormal septal bounce on echo are signs of ventricular electromechanical delay or dyssynchrony, which can result in reduced ventricular systolic function, altered myocardial metabolism, functional mitral regurgitation, and adverse remodeling with ventricular dilatation 1.
Clinical Implications
- Patients with LBBB and left ventricular systolic dysfunction may benefit from cardiac resynchronization therapy (CRT), which can improve ventricular systolic function, reduce metabolic costs, ameliorate functional mitral regurgitation, and induce favorable remodeling 1.
- The presence of LBBB and left ventricular systolic dysfunction should prompt consideration for further evaluation and management, including echocardiography and cardiac MRI 1.
- In patients with LBBB and left ventricular systolic dysfunction, techniques that provide more physiologic ventricular activation, such as CRT or His bundle pacing, are preferred to right ventricular pacing to prevent heart failure 1.
From the Research
Left Bundle Branch Dysynchrony and Abnormal Septal Bounce on Echocardiogram
- Left bundle branch (LB) branch dysynchrony and abnormal septal bounce on echocardiogram (echo) are indicators of mechanical dyssynchrony in patients with left bundle branch block (LBBB) 2, 3, 4, 5, 6
- Studies have shown that LBBB is associated with delayed left ventricular systolic and diastolic events, resulting in shortening of left ventricular diastole and increased ratio of right to left ventricular diastolic time 2
- Abnormal interventricular septal motion in LBBB corresponds to periods of asynchrony in contraction, ejection, end systole, and end diastole between right and left ventricles 2
- Septal flash (SF) is a common feature in patients with LBBB, present in 45.2% of LBBB patients, and is associated with longer QRS duration and lower ejection fraction 4
- The presence of mid-QRS notching in more than two consecutive leads is a good predictor for the presence of SF, and when combined with an absent R-wave in lead V1, the presence of SF is very likely 4
Echocardiographic Features
- Echocardiographic findings in LBBB include abnormal septal motion, septal flash, and delayed left ventricular free-wall contraction 3, 5
- Septal displacement curves generated using feature-tracking techniques can help evaluate mechanical dyssynchrony in patients with LBBB 3
- Cardiac magnetic resonance imaging (CMR) can be used to identify and evaluate mechanical dyssynchrony in patients with LBBB, including features such as septal flash, apical rocking, and delayed aortic valve opening 3
Clinical Implications
- The presence of LBBB and mechanical dyssynchrony can lead to reduced left ventricular ejection fraction (LVEF) and decreased cardiac output 2, 6
- Patients with LBBB and cardiac dyssynchrony may benefit from cardiac resynchronization treatment (CRT) 3, 4
- The evaluation of mechanical dyssynchrony using echocardiography and CMR can help identify patients who may benefit from CRT 3, 4