Interventricular Conduction Delay (QRS widening)

Definition

• 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 hyperkalaemia and tricyclic antidepressant poisoning.

Causes

Follow the links to read more about each condition.

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

Electrolyte abnormalities

• Hyperkalaemia

Toxins

• Sodium-channel blocker toxicity (e.g. TCA overdose) - wide QRS plus positive R’ wave in aVR.

Pre-excitation

• Wolff-Parkinson-White syndrome – wide QRS plus delta waves.

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.

“Non-specific” IVCD

• 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.

Differential Diagnosis

Ventricular Rhythms

• Ventricular tachycardia
• Accelerated idioventricular rhythm
• Ventricular escape rhythm
• Ventricular-paced rhythm

 

Further Reading

• ECG BASICS – Waves, Intervals, Segments and Clinical Interpretation
• ECG CLINICAL CASES – Your favourite ECG’s placed in clinical context with a challenging Q&A approach
• ECG and Cardiology Eponymous Syndromes – Cheats guide to eponymous emancipation
• ECG Reference Sites on the WEB – the best of the rest

Author Credits

• Words – Ed Burns
• Pictures – Ed Burns
• Web Editing – Ed Burns

References

• Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.
• 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. Review. PubMed PMID: 12028984; PubMed Central PMCID: PMC1123219 [