Intraventricular 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 Intraventricular 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


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Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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