broad QRS complex

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A normal QRS complex is less than 2.5 small squares wide. Greater than 3 is broad; implying bundle branch block or other pathology; between 2.5 and 3 implies partial bundle branch block.

For analysis, choose lead in which QRS appears the widest, and count the squares in that lead.

Note that an early, broad, abnormal QRS complex may be a ventricular ectopic; ie if the depolarisation has been initiated by a focus in the ventricular muscle.

Last reviewed 01/2018