What condition is characterized by a prolonged PR interval?

A prolonged PR interval is indicative of a delay in conduction through the atrioventricular (AV) node, which is characteristic of first-degree AV block. In this condition, the time it takes for the electrical impulse to travel from the atria to the ventricles is longer than normal, resulting in a PR interval that exceeds 0.20 seconds. This delay does not necessarily affect the overall heart rate or rhythm, but it does point to a disruption in the normal conduction pathway of the heart.

In contrast, atrial fibrillation is characterized by an irregularly irregular rhythm and the absence of distinct P waves, rather than a prolonged PR interval. Ventricular tachycardia is a rapid heart rhythm originating from the ventricles, typically featuring broad QRS complexes and not related to the PR interval duration. Supraventricular tachycardia involves rapid rhythms originating above the ventricles and does not include a prolonged PR interval; instead, it may present with a shortened or normal PR interval depending on the specific type.

Understanding these concepts highlights how each condition impacts the electrical activity of the heart differently, thus reinforcing why first-degree AV block is specifically associated with a prolonged PR interval.