Bundle Branch Block Pathophysiology and Management

Mechanism and Etiologies

• The American College of Cardiology notes that right bundle branch block results from interruption of conduction through the right bundle branch, causing delayed right ventricular activation that manifests as QRS duration >120 ms on ECG, with a prevalence of approximately 1% in the general population, and 0.6% in males under 40 years 1
• The European Heart Journal reports that ischemic heart disease, especially anterior myocardial infarction with persistent intraventricular conduction disturbances, carries an unfavorable prognosis 2
• Hypertensive heart disease is a recognized structural cause of both RBBB and LBBB, according to the American College of Cardiology 1
• The American College of Cardiology states that cardiomyopathies of various types can produce bundle branch block 1
• The Journal of the American College of Cardiology found that left ventricular systolic dysfunction is markedly more likely when LBBB is present on ECG 3

Clinical Significance and Prognosis

• The European Heart Journal notes that isolated RBBB in patients with normal hearts does not appear to reflect adverse outcomes 2
• The European Heart Journal reports that in patients with myocardial infarction receiving thrombolytic therapy, BBB identifies a subset at high risk 2
• The European Heart Journal states that the most frequent cause of sudden cardiac death in patients with bifascicular block is ventricular tachyarrhythmia, mainly occurring in those with coronary artery disease, heart failure, and/or advanced age 2

Management Approach

• The American College of Cardiology recommends that in patients with newly detected LBBB, transthoracic echocardiography to exclude structural heart disease is mandatory (Class I recommendation) 3
• The American College of Cardiology suggests that for RBBB with suspected structural heart disease, transthoracic echocardiography is reasonable (Class IIa) 3
• The American College of Cardiology states that advanced imaging (cardiac MRI, CT, or nuclear studies) is reasonable when echocardiography is unrevealing but structural disease is suspected 3
• The European Heart Journal notes that permanent pacing is indicated (Class I) for bundle branch block with syncope when EPS demonstrates HV interval ≥70 ms or frank infranodal block 4
• The American College of Cardiology states that isolated asymptomatic bundle branch block with 1:1 AV conduction does NOT require pacing (Class III: Harm) 6