Normal QRS Duration
Normal QRS Duration by Age Group
- The American College of Cardiology and Circulation guideline recommends that in adults, QRS duration is normally less than 120 milliseconds 1, 2, 3, 4
- The American College of Cardiology guideline states that in children 4-16 years, QRS duration is normally less than 100 milliseconds 2, 5
- The American College of Cardiology and Circulation guideline recommends that in children under 4 years, QRS duration is normally less than 90 milliseconds 1, 2
Borderline QRS Duration
- The American College of Cardiology guideline states that in adults, QRS duration between 110-119 milliseconds is considered borderline and may represent incomplete bundle branch block 2, 5
- The American College of Cardiology guideline recommends that in children 8-16 years, QRS duration between 90-100 milliseconds is considered borderline 2
- The American College of Cardiology guideline states that in children under 8 years, QRS duration between 80-90 milliseconds is considered borderline 5
Clinical Significance of QRS Duration
- QRS duration represents ventricular depolarization time and should be present in all standard ECG leads in normal cardiac conduction, according to the American College of Cardiology 6
- Prolonged QRS duration (≥120 ms) is a marker of intraventricular conduction delay, which may indicate complete right or left bundle branch block, according to the American College of Cardiology and Circulation guidelines 2, 3, 4
Common Pitfalls in QRS Measurement
- Failure to recognize age-dependent normal values is a common pitfall in QRS measurement, according to the American College of Cardiology and Circulation guidelines 1, 2
- Confusing incomplete bundle branch block (QRS 110-119 ms) with normal QRS duration is a common pitfall, according to the American College of Cardiology guideline 2, 5