Which statement describes second degree heart block type 1 (Wenkebach)?

The statement that describes second-degree heart block type 1, also known as Wenkebach, is the one that indicates the PR interval progressively lengthens until a beat is dropped. This characteristic is a hallmark of Wenkebach phenomena. In this condition, the conduction through the atrioventricular (AV) node is impaired, leading to a gradual prolongation of the PR interval with each successive heartbeat. Eventually, this results in a failure of one impulse to be conducted to the ventricles, causing a dropped beat.

This progressive pattern reflects the underlying physiology of Wenkebach, where there is an intermittent failure in conduction rather than a complete block. As such, the rhythm is characterized by alternating cycles of conducted and non-conducted beats, signifying a typical manifestation of second-degree heart block type 1. This unique behavior in the PR interval is critical for differentiating Wenkebach from other types of heart block.