Left bundle branch block

Causes

• Aortic stenosis
• Dilated cardiomyopathy
• Acute myocardial infarction
• Extensive coronary artery disease
• Primary disease of the cardiac electrical conduction system
• Long standing hypertension leading to aortic root dilatation and subsequent aortic regurgitation
• Lyme disease
• Side effect of some cardiac surgeries

  Diagnosis

• The heart rhythm must be supraventricular in origin
• The QRS duration must be ≥ 120 ms
• There should be a QS or rS complex in lead V1
• There should be a notched R wave in lead V6.

Diagnostic consequences

Treatment

• Patients with LBBB require complete cardiac evaluation, and those with LBBB and syncope or near-syncope may require a pacemaker.
• Some patients with LBBB, a markedly prolonged QRS, and systolic heart failure may benefit from a biventricular pacemaker, which allows for better synchrony of heart contractions.