How does a Mobitz AV block present in terms of P to QRS ratio?

How does a Mobitz AV block present in terms of P to QRS ratio?

• A. Multiple QRS complexes for each P wave
• B. Only one QRS complex follows several P waves
• C. Equal number of QRS complexes and P waves
• D. Two QRS complexes following each P wave

Answer: (B)

In a Mobitz AV block, specifically Mobitz type I (Wenckebach) or Mobitz type II, the defining characteristic is that there are instances where P waves do not conduct to the ventricles, resulting in missing QRS complexes. This leads to a situation where there are more P waves than QRS complexes.

In the Mobitz type I variation, the pattern usually shows a gradual lengthening of the PR interval until a P wave is not followed by a QRS complex. After this dropout, the cycle generally repeats. In Mobitz type II, the ratio can vary, but the presence of P waves that are not immediately followed by a QRS complex still exists. Therefore, it's not unusual to observe multiple P waves without a corresponding QRS complex, leading to the conclusion that, in terms of P to QRS ratio, there will be instances of one P wave that does not lead to a QRS complex, representing the relationship as one P wave followed by several P waves without a QRS response.

This differentiation in the presentation helps identify the specific type of AV block, which is crucial for appropriate management and treatment strategy for patients experiencing these cardiac conduction abnormalities.