What are the diagnostic criteria and treatment options for a right bundle branch block (RBBB)?

Right Bundle Branch Block Diagnosis

Diagnostic Criteria for Complete RBBB

Complete RBBB is diagnosed when all three criteria are met: QRS duration ≥120 ms in adults, characteristic rsr'/rsR'/rSR' pattern in leads V1 or V2, and S wave duration greater than R wave or >40 ms in leads I and V6. 1, 2

Essential ECG Criteria (All Must Be Present)

QRS Duration Requirements:

• Adults: ≥120 ms 1, 2
• Children ages 4-16 years: ≥100 ms 2
• Children <4 years: ≥90 ms 2

Morphologic Features:

• rsr', rsR', rSR', or rarely qR pattern in leads V1 or V2, where the R' or r'' deflection is usually wider than the initial R wave 1, 2
• In a minority of patients, a wide and often notched R wave pattern may appear in lead V1 and/or V2 1
• S wave of greater duration than R wave OR >40 ms in leads I and V6 1, 2
• Normal R peak time in leads V5 and V6 but >50 ms in lead V1 1, 2

Diagnostic Criteria for Incomplete RBBB

Incomplete RBBB shares identical morphologic features as complete RBBB but with shorter QRS duration: 110-119 ms in adults. 3, 2

QRS Duration Thresholds by Age:

• Adults: 110-119 ms 3, 2
• Children ages 4-16 years: 90-100 ms 3, 2
• Children <8 years: 86-90 ms 3, 2

Morphologic Requirements (Identical to Complete RBBB):

• rsr', rsR', or rSR' pattern in leads V1 or V2 3, 2
• S wave of greater duration than R wave or >40 ms in leads I and V6 3
• Normal R peak time in leads V5 and V6 but >50 ms in lead V1 3
• In children, incomplete RBBB may be diagnosed when the terminal rightward deflection is ≥20 ms but <40 ms with other criteria present 3

Critical Diagnostic Pitfalls to Avoid

Normal Variants That Mimic RBBB:

An rsr' pattern in V1 and V2 with normal QRS duration is a normal variant in children and should NOT be labeled as incomplete RBBB. 3, 2

• This pattern may appear when lead V1 is recorded higher than or to the right of normal position, particularly when the r' is <20 ms 3
• The terms "rsr'" and "normal rsr'" should not be used to describe these patterns because their meaning can be variously interpreted 3

Important Exclusion Criteria:

• These diagnostic criteria do NOT apply to patients with congenital heart disease who have left-axis deviation present in infancy 3, 2

Pathological Patterns Requiring Differentiation:

Clinicians must differentiate RBBB from several pathological conditions that can present with similar ECG patterns: 4

• Type-2 Brugada ECG pattern - critical to identify due to sudden cardiac death risk 4
• Right ventricular enlargement 4
• Arrhythmogenic right ventricular cardiomyopathy 4
• Ventricular preexcitation (Wolff-Parkinson-White syndrome) 4
• Hyperkalemia 4

Special Clinical Consideration:

Be particularly alert to splitting of the second heart sound on physical examination, as RBBB is a common finding in ostium secundum atrial septal defect. 4

High-Risk RBBB Pattern Recognition

RBBB with a QR pattern in V1 has high positive predictive value for diagnosing cardiac arrest caused by high-risk pulmonary embolism. 5

• The presence of a QR pattern in V1 serves as an independent predictor for high-risk PE patients who may require advanced treatments including systemic thrombolysis or invasive embolectomy 5
• This pattern should prompt urgent consideration of PE in the appropriate clinical context, particularly in patients presenting with sudden cardiac arrest 5

Enhanced Diagnostic Accuracy

Body surface potential mapping (BSPM) with 64-lead recordings can improve RBBB diagnosis sensitivity to 93% compared to 76.9% with standard 12-lead ECG alone. 6

• QRS duration measured from BSPM information can be 15.3 ± 10.8 milliseconds longer than standard 12-lead ECG measurement, particularly in RBBB with left anterior fascicular block 6

Treatment Approach

In asymptomatic patients with isolated RBBB and no evidence of cardiovascular disease, no specific treatment is required beyond routine cardiovascular risk factor management. 7

Risk Stratification:

• At initial diagnosis, 94% of RBBB patients have no evidence of cardiovascular disease 7
• During follow-up, new coronary heart disease develops in only 6% of RBBB patients 7
• Progressive electrical dysfunction to complete heart block is rare, occurring in only 1% of cases 7
• Mortality rate is approximately 4% during long-term follow-up 7

When Further Evaluation Is Needed:

If abnormalities are found on clinical examination, comprehensive cardiac evaluation should be performed to exclude underlying heart disease. 4

• Evaluate for structural heart disease if RBBB is accompanied by symptoms, family history of sudden cardiac death, or left ventricular hypertrophy 4
• Consider echocardiography to assess for atrial septal defect, right ventricular enlargement, or cardiomyopathy 4
• In athletes with RBBB, the pattern is generally considered benign unless accompanied by concerning features 4