If the QRS duration is greater than 0.10 seconds, what does it indicate?

A QRS duration greater than 0.10 seconds indicates a delay in the conduction of electrical impulses through the ventricles of the heart. This is referred to as an intraventricular conduction delay. The QRS complex represents the depolarization of the ventricles, and when the duration is prolonged, it suggests that the electrical signals are not being transmitted through the ventricles in the typical time frame. This can result from various factors, including the presence of a bundle branch block or other conduction abnormalities.

In contrast, normal conduction would typically produce a QRS duration of less than 0.10 seconds. Similarly, atrial enlargement usually affects the P wave rather than the QRS complex, and while myocardial infarction can lead to abnormalities in the QRS complex, it does not specifically signify a lengthened duration unless associated with other conditions like a conduction delay. Thus, the indication of a QRS duration exceeding 0.10 seconds most specifically points to an intraventricular conduction delay rather than these other conditions.