In a 2nd Degree AV Block Type 1, what happens to the PR interval?

In a 2nd Degree AV Block Type 1, also known as Wenckebach, the key characteristic is the progressive lengthening of the PR interval with each successive heartbeat until a P wave is blocked, leading to a dropped QRS complex. This phenomenon occurs due to a gradual increase in the time it takes for the electrical impulse to travel from the atria to the ventricles through the AV node. As the conduction through the AV node becomes increasingly delayed, the PR interval becomes longer. Eventually, this delay reaches a point that prevents the electrical impulse from passing through, resulting in a blocked P wave and the subsequent loss of the QRS complex. Hence, the behavior of the PR interval in this block is recognizable and distinctive, making it an important diagnostic feature in interpreting ECGs.