Definition of QRS widening
QRS duration > 100 ms in the presence of a supraventricular rhythm. Most commonly due to bundle branch block or left ventricular hypertrophy.
The most important life-threatening causes of QRS widening are:
Causes of Interventricular Conduction Delay
Fascicular and bundle-branch blocks
- Left anterior fascicular block
- Left posterior fascicular block
- Left bundle branch block
- Right bundle branch block
- Bifascicular block
- Trifascicular block
Ventricular hypertrophy and dilatation
- Left ventricular hypertrophy
- Right ventricular hypertrophy
- Biventricular enlargement
- Dilated cardiomyopathy
- Sodium-channel blocker toxicity (e.g. TCA overdose) – wide QRS plus positive R’ wave in aVR.
Arrhythmogenic cardiac conditions
- Brugada syndrome – localised QRS widening in V1-2 with RBBB morphology.
- Arrhythmogenic right ventricular dysplasia (AVRD) – localised QRS widening in V1-2 plus epsilon waves and variable signs of right ventricular hypertrophy.
- Not due to any of the causes above — Before making this diagnosis, be sure to check the serum potassium level and scrutinise the ECG for any signs of TCA toxicity.
- Ventricular tachycardia
- Accelerated idioventricular rhythm
- Ventricular escape rhythm
- Ventricular-paced rhythm
- Edhouse J, Thakur RK, Khalil JM. ABC of clinical electrocardiography. Conditions affecting the left side of the heart. BMJ. 2002 May 25;324(7348):1264-7 PMCID: PMC1123219
LITFL Further Reading
- ECG Library Basics – Waves, Intervals, Segments and Clinical Interpretation
- ECG A to Z by diagnosis – ECG interpretation in clinical context
- ECG Exigency and Cardiovascular Curveball – ECG Clinical Cases
- 100 ECG Quiz – Self-assessment tool for examination practice
- ECG Reference SITES and BOOKS – the best of the rest
- Brady WJ, Truwit JD. Critical Decisions in Emergency and Acute Care Electrocardiography
- Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric
- Wagner GS. Marriott’s Practical Electrocardiography 12e
- Chan TC. ECG in Emergency Medicine and Acute Care
- Rawshani A. Clinical ECG Interpretation
- Mattu A. ECG’s for the Emergency Physician
- Hampton JR. The ECG In Practice, 6e