Interventricular Conduction Delay (QRS widening)

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

Ventricular hypertrophy and dilatation

Electrolyte abnormalities



Arrhythmogenic cardiac conditions

“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


  • 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

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Posted by Dr Ed Burns

Dr Ed Burns . Emergency Physician in Pre-hospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education. Ed is the force behind the LITFL ECG library | + Edward Burns | @edjamesburns

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