What is the RCG (Right Bundle Branch Block) feature of RBBB (Right Bundle Branch Block)?

ECG Features of Right Bundle Branch Block (RBBB)

Right bundle branch block (RBBB) is characterized by specific ECG findings including QRS duration ≥120 ms in adults, an rSR' pattern in leads V1-V2, and S waves of greater duration than R waves in leads I and V6. 1

Diagnostic Criteria for Complete RBBB

• QRS duration ≥120 ms in adults (>100 ms in children 4-16 years, >90 ms in children <4 years) 1
• rSR', rsR', or rSR pattern in leads V1 or V2, with the R' deflection usually wider than the initial R wave 1
• S wave of greater duration than R wave or >40 ms in leads I and V6 in adults 1
• Normal R peak time in leads V5 and V6 but >50 ms in lead V1 1

Morphological Variations

• The classic RBBB pattern shows an rSR' configuration in right precordial leads (V1-V2) 1
• In some cases, a wide and often notched R wave pattern may be seen in leads V1 and/or V2 instead of the typical rSR' pattern 1
• RBBB reduces the amplitude of the S wave in the right precordial leads 1
• The morphological diversity in RBBB patterns is related to multiple factors including site of block, nature of defect, degree of conduction delay, and associated pathologies 2

Distinguishing Features from Other Conditions

• Complete RBBB must be differentiated from incomplete RBBB, which has a QRS duration between 110-120 ms in adults 1
• In the presence of pre-existing left bundle branch block, RBBB may present with absent S waves in leads I and aVL, which is 100% specific and 64% sensitive for bilateral bundle branch delay 3
• RBBB with a QR pattern in V1 has a high positive predictive value for diagnosing cardiac arrest caused by high-risk pulmonary embolism 4

Clinical Significance

• Although incomplete RBBB is common in young athletes, complete RBBB is less common with a prevalence of 0.5% to 2.5% in young adult athletes 1
• Complete RBBB is detected in approximately 1% of the general population 1
• In athletes with complete RBBB, studies have shown larger right ventricular dimensions and lower right ventricular ejection fraction but preserved fractional area change compared to those with normal QRS complexes 1
• These patterns may represent a spectrum of structural and physiological cardiac remodeling characterized by RV dilation with resultant QRS prolongation 1

Evaluation Recommendations

• Demonstration of complete bundle branch block should lead to a cardiological work-up including exercise testing, 24-hour ECG monitoring, and imaging to evaluate for underlying pathological causes 1
• The ancillary features of left atrial abnormality and left axis deviation have enhanced value for the diagnosis of left ventricular hypertrophy in the presence of RBBB 1
• Special criteria for LVH in the presence of RBBB include S V1 >2 mm (0.2 mV), R V5,6 >15 mm (1.5 mV), and QRS axis to the left of -30° 1

Potential Complications

• RBBB may be associated with underlying cardiovascular disorders, though it can also be an isolated and clinically benign finding 1
• In patients with tetralogy of Fallot, RBBB is present in the vast majority of patients after repair, and SVTs are conducted with RBBB aberrancy 1
• In Ebstein's anomaly, RBBB is usually present and may be masked by ventricular pre-excitation in the presence of a right-sided accessory pathway 1