A bradycardic rhythm at 36/minute with P’s before each QRS and another P wave following the QRS that does not conduct. There is also a wide QRS complex consistent with a LBBB.

This rhythm is either 2:1 AV block (a 2° AV block of undetermined type) or atrial bigeminy with blocked PACs. If this is 2:1 AV block, the P waves should be regular…and they are not in this tracing! This is a notorious and well-described masquerader of high-grade AV block. Remember Dr. Marriott’s recommendation “cherchez la P.”

Compare this week’s EKG rhythm strip

…with a similar appearing rhythm that does have regular P waves, and therefore is likely 2:1 AV block