ECG Question #21


During an admission assessment, a client informs the nurse of a history of having a certain type of heart block. Previous records were analyzed by the nurse and the client was found to have the following ECG the previous year.

The nurse interprets last year’s ECG as:


  1. First degree AV block
    • Rationale:
  2. Sick sinus syndrome
    • Rationale:
  3. Second degree AV type I (Wenckebach)
    • Rationale:
  4. Third degree AV block
    • Rationale:



The Mobitz type I is also known as Wenckebach block and indicates failure of conduction through the AV node. Some P waves may not be followed by the QRS complex. This form of block differs from first degree block. First degree block maintains a 1:1 P wave:QRS ratio; whereas, second degree block will have an increasing delay of AV nodal conduction until a P wave fails to conduct through the AV node. It progresses until the P wave is not conducted. The R-R is usually irregular. The block could be caused by medications, ischemic episode, infection, and heart surgery. This rhythm does not indicate sick sinus syndrome or third degree AV block.

Learning Outcomes

Test Taking Tip

Video Rationale