Is a QRS (Quadrature Amplitude Modulation duration of the Q, R, and S waves in an electrocardiogram) duration of 113 milliseconds consistent with Right Bundle Branch Block (RBBB) in a 13-year-old female?

QRS Duration of 113 ms in a 13-year-old Female and RBBB

A QRS duration of 113 ms in a 13-year-old female is consistent with incomplete right bundle branch block (RBBB) according to established guidelines. 1

Understanding QRS Duration Norms by Age

The American College of Cardiology/American Heart Association/Heart Rhythm Society guidelines provide clear criteria for QRS duration norms by age:

• Adults: Normal QRS ≤110 ms
• Children 4-16 years: Normal QRS <100 ms
• Children <4 years: Normal QRS <90 ms 2

For a 13-year-old, the normal QRS duration should be <100 ms. Therefore, 113 ms represents a prolongation beyond the normal range for this age group.

RBBB Classification Criteria

According to the 2018 ACC/AHA/HRS guidelines, RBBB is classified as:

• Complete RBBB: QRS duration ≥120 ms with specific morphology criteria
• Incomplete RBBB: Same morphology criteria as complete RBBB but with QRS duration between 110-119 ms 1

The patient's QRS duration of 113 ms falls within the range defined for incomplete RBBB (110-119 ms).

Clinical Implications

• Incomplete RBBB in pediatric patients is often a benign finding but may warrant further evaluation to rule out underlying structural heart disease
• The presence of RBBB pattern should prompt assessment of:
  • Right ventricular size and function
  • Pulmonary artery pressure
  • Presence of atrial or ventricular septal defects

Important Considerations

1. Morphology matters: While QRS duration of 113 ms meets the timing criteria for incomplete RBBB, confirmation requires the presence of specific morphology features:

   • rsr', rsR', or rSR' pattern in leads V1 or V2
   • S wave of greater duration than R wave or >40 ms in leads I and V6 1

2. Differential diagnosis: Nonspecific intraventricular conduction delay should be considered if RBBB morphology criteria are not met despite prolonged QRS duration 1

3. Clinical correlation: Unlike left bundle branch block, RBBB is not commonly associated with left ventricular systolic dysfunction 3, but can be associated with right ventricular dysfunction when R' wave duration in lead V1 is prolonged (≥93 ms) 4

Follow-up Recommendations

• Echocardiography to evaluate for structural heart disease, particularly right heart abnormalities
• Serial ECGs to monitor for progression to complete RBBB
• Cardiac evaluation if associated with symptoms such as syncope, palpitations, or exercise intolerance

Pitfalls to Avoid

• Don't assume RBBB is always benign in pediatric patients; consider screening for underlying structural heart disease
• Avoid misclassifying as complete RBBB, which requires QRS duration ≥120 ms
• Don't confuse with nonspecific intraventricular conduction delay, which has prolonged QRS but lacks specific RBBB morphology

In conclusion, the 113 ms QRS duration in this 13-year-old female is consistent with incomplete RBBB according to established guidelines, assuming the characteristic RBBB morphology is present on ECG.