There is progressive prolongation of the PR interval with a "dropped beat" (actually, a P wave without a QRS) every 3rd beat. This progressive prolongation of the PR interval is characteristic of 2nd degree type I heart block, also called "Wenckebach" or "Mobitz 1". Wenckebach usually produces grouped beating patterns (a so-called "footprint" of the Wenckebach phenomenon). This one has 3 P waves to 2 ventricular complexes, and is called "3:2" Wenckebach. The overall heart rate is normal.zz
Because Type I 2nd degree/Mobitz 1 is usually caused by high vagal tone, and is a fluctuating dysrhythmia, a pacer is not usually indicated. The rhythm can be seen in healthy young people, athletes, and during activities/experiences that increase vagal tone. In contrast Mobitz 2 is usually due to intrinsic conduction system disease and may herald the development of complete heart block.
NOTE: EKG's are for internal educational purposes of the University of Massachusetts Department of Family Medicine. Please do not forward without permission from Dr. Golding!
