Why is it important not to miss the Mobitz Blocks?

Some of these will deteriorate and develop into worsening blocks which may compromise the patient.

Causes of Mobitz Blocks

MOBITZ I

• Suppression of AV conduction
• Ischaemia
• Drugs

MOBITZ II

• Failre of conduction at the His-Purkinge system below the AVN
• AMI
• Hyperkalemia
• Drugs
  • Beta blockers
  • Amiodarone
  • Calcium channel blockers
  • Digoxin
• Fibrosis of the conducting system
• Inflammatory causes
  • Myocarditis
  • Rheumatic Fever
• Autoimmune disease ie., SLE

---

How to Diagnose a Mobitz Block

If the rate is slow, we need to look for a block

1. Are there more P's than QRS's
2. If yes then ask what the P-P interval is doing
   1. If the P-P interval is constant, then look for a MOBITZ block: Loop at the PR interval
      1. If the PR interval is progressively increasing, then there is a drop of a QRS it is a WENCKEBACH
      2. If the PR interval is nor changing, but regularly a QRS is dropped, then it is a MOBITZ II block
         1. Beware the ECGs where the second P wave is hidden in the T wave
      3. If the PR interval is totally irregular ie., wide, narrow, very wide, ie no relationship to the QRS, then it is a COMPLETE HEART BLOCK
   2. If the P-P interval is not constant think of premature atrial contraction (PAC)

Try these ECGs

Below is a group of ECGs.
Click on each one, or go to your workbook and write down what the diagnosis of each one is.
Once you have tried them, go to the answers below to find out the results.

ECG 1

A 23 yo soccer player presents with ankle pain. For some reason an ecg is done and the nurse is concerned. What is the diagnosis?

Also refer to ECG changes in athletes for what is normal and what is not.

---

Here are the ANSWERS

ECG 1. ​A 23 yo soccer player presents with ankle pain. For some reason an ecg is done and the nurse is concerned. What is the diagnosis?

WENCKEBACK BLOCK