What abnormality does a wide QRS complex indicate?

A wide QRS complex indicates a delay in the conduction of electrical impulses through the heart's ventricles. Specifically, this suggests that there may be an issue with the pathways that transmit these impulses, particularly in the context of a bundle branch block. In a bundle branch block, the electrical conduction is impeded in either the right or left bundle branch, causing the QRS duration to widen beyond the typical duration of 0.06–0.10 seconds.

This widening occurs because the impulse travels more slowly through the affected branch, leading to asynchronous contraction of the ventricles. The significance of a wide QRS complex lies in its association with various cardiac conditions, yet the presence of a bundle branch block is one of the most common explanations.

While other conditions like atrial fibrillation, myocardial infarction, or normal variants can influence the heart's electrical activity, they typically do not lead to a wide QRS complex in the same way that a bundle branch block does. Thus, recognizing that a wide QRS is largely indicative of conduction abnormalities, specifically relating to the bundle branches, highlights the importance of understanding the underlying causes of electrocardiogram findings.