Q 1: How do you read this EKG ?

Q 2: What are the characteristics of this defect?

Answer

Answers

Q 1: How do you read this EKG strip?

1 Degree A-V block

Q 2: What are the characteristics of this defect?

• PR interval 0.21 or greater
• All P waves  followed by QRS complexes
• the block is located proximal to the bifurcation of the bundle branches in AV node

PR Interval

The PR interval indicates AV conduction time which is normally between 0.12 - 0.20 msec (3 - 5 boxes wide). If the PR interval is greater than 0.2 sec, then an AV block is present. There are several types of AV blocks:

• 1st degree AV Block: PR>0.20 sec.
• 2nd degree AV Block: 2 types:
  1. Type I (Mobitz I or Wenckeback): increasing PR interval until a QRS complex is dropped. It is usually benign.
  2. Type 2 (Mobitz II): QRS dropped without any progressive increase in PR interval (i.e., PR interval is constant but still >0.20 sec). Here's an example.
• 3rd degree AV Block: atria and ventricles are electrically dissociated. Therefore, P waves and QRS complexes will occur independent of each other. As always, use the QRS complexes to determine heart rate. Here's an example.