ECG Workshop: Look carefully

A 69 M presents with episodes of presyncope.

The first ECG is done and handed to you.

You have a quick look and mutter something about 2nd degree AV Block at 2:1 and wander off to the trauma code.

When you get back, you decide to have a better look and print out a longer strip of the central monitor

In this rhythm strip, you can clearly see the p waves catching up to and then overtaking the QRS – definitively proving AV dissociation and thus 3rd degree AV block

You can get doubts about 3rd degree AVB when the p wave rate is close to the same as, or a multiple of, the QRS rate.

Always looking at a bit of a longer rhythm strip will help!