A 76 year old woman is seen on the general surgery floor after recent abdominal surgery because of an abnormal ECG as pictured below.  The patient is asymptomatic.

• Sinus rhythm with both Mobitz I Second Degree AV Block and 2:1 AV Block with intermittent junctional escape complexes (labelled J)

Comment: The longer PR interval in the second and sixth beats suggest Mobitz I Second Degree AV Block is present. Although there is a P-wave before some of the junctional escape complexes, they cannot be conducted beats as the PR interval is too short.