Prolonged QRS Interval
April 24th, 2019
Overview
The duration of the QRS interval is useful for determining the origin of an abnormal rhythm, particularly in the setting of tachycardia.
Normal Duration
- 80 - 120ms (2-3mm)
Interpretation
- Narrow QRS complexes (<120ms) - indicative of a supraventricular rhythm from the SA node, atria or AV node.
- Wide QRS complexes - indicative of a ventricular rhythm, or aberrant conduction of a supraventricular rhythm.
Causes of Wide QRS Complexes
Ventricular Origin
- Premature ventricular complexes
- Ventricular tachycardia
- Pacemaker rhythm
Aberrant Conduction
- Bundle branch block
- Accessory pathway, e.g. Wolff-Parkinson-White
- Hyperkalaemia
- Sodium channel blocker toxicity - tricyclic antidepressants, type I antiarrhythmics, local anaesthetics
Example
- Wide QRS complexes in the setting of left bundle branch block.
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