What is the clinical significance of a right bundle branch block (RBBB) in a 62-year-old male?

From the Guidelines

Right bundle branch block (RBBB) in a 62-year-old man is generally considered a benign finding if the patient is asymptomatic and has no underlying heart disease, but it warrants a baseline cardiac evaluation including an echocardiogram to rule out structural heart disease, as recommended by the 2018 ACC/AHA/HRS guideline 1. The clinical significance of RBBB depends on the context - it may be a marker of underlying cardiac disease such as coronary artery disease, cardiomyopathy, or valvular heart disease in this age group 1.

Key Considerations

• RBBB occurs when electrical conduction through the right bundle branch is delayed or blocked, causing the right ventricle to depolarize after the left ventricle.
• This creates characteristic ECG findings including a wide QRS complex (>120 ms), an RSR' pattern in V1-V3 (often described as "rabbit ears"), and wide S waves in leads I and V6.
• According to the guideline, patients with RBBB or intraventricular conduction delay on ECG also have increased risk of left ventricular systolic dysfunction compared with those with completely normal ECGs, yet the yield is lower than those patients with LBBB 1.

Diagnostic Approach

• Electrocardiography is the primary method of diagnosing potential conduction disorders 1.
• An echocardiogram may uncover treatable disease, or impact management decisions such as cardiac resynchronization device placement 1.
• Ambulatory electrocardiographic monitoring can be used to document clinically significant arrhythmias in asymptomatic patients as well 1.

Management

• No specific treatment is required for isolated RBBB, but the patient should be monitored for development of symptoms like syncope, presyncope, or heart failure 1.
• If the patient develops symptoms or if RBBB is accompanied by left anterior or posterior fascicular block (bifascicular block), closer monitoring and possibly additional interventions may be necessary due to increased risk of progression to complete heart block 1.

From the Research

Clinical Significance of Right Bundle Branch Block

• Right bundle branch block (RBBB) is characterized by a prolongation of the QRS complex, RR' or rR' appearances in V1, and widened S waves in leads exploring the left ventricle 2.
• The prognosis of RBBB in the absence of underlying cardiac disease is generally good, but it may be poor in cases of coronary artery disease or other cardiac conditions 2.
• RBBB can be a predictor of sudden cardiac arrest due to pulmonary embolism, particularly when associated with a QR pattern in V1 on the electrocardiogram (ECG) 3.

Diagnostic Considerations

• The principal differential ECG diagnosis for RBBB is Brugada syndrome, a familial arrhythmogenic autosomal dominant cardiomyopathy of variable penetration 2.
• RBBB can also be associated with arrhythmogenic right ventricular cardiomyopathy (ARVC), and the chamber of origin of RBBB ventricular tachycardia can be determined based on standard mapping criteria and elimination with ablation 4.
• In patients with suspected myocardial infarction, RBBB is considered a high-risk factor for mortality, but the likelihood of myocardial infarction is equally frequent in patients without bundle branch block 5.

Prognostic Implications

• The presence of RBBB with a QR pattern in V1 on ECG has a high positive predictive value for diagnosing cardiac arrest caused by high-risk pulmonary embolism 3.
• RBBB is associated with a higher mortality rate in patients with suspected myocardial infarction, particularly when compared to those without complete block 5.
• The prognosis of RBBB to complete atrioventricular block is rare in the absence of associated cardiac disease 2.