Multiple P wave blocks correspond to which second-degree block type?

Multiple P wave blocks correspond to which second-degree block type?

• A. 1st Degree
• B. 2nd Degree Type 2
• C. 3rd Degree
• D. 2nd Degree Type 1

Answer: (B)

Understanding how atrial impulses are conducted to the ventricles helps classify second-degree AV block. In this type, some P waves fail to conduct to the ventricles, causing a dropped QRS complex. When you see several P waves in a row followed by a single dropped QRS, with the PR interval remaining the same for the beats that do conduct, that pattern points to Mobitz II. This contrasts with Wenckebach (Mobitz I), where you’d see a gradual slowing of conduction—the PR interval lengthens progressively until a beat drops. In complete heart block (third degree), there’s no consistent relationship between P waves and QRS complexes at all—the atria and ventricles beat independently. First-degree block shows a single, steadily prolonged PR interval with every P wave still conducting. Mobitz II is often due to disease in the His-Purkinje system and carries a higher risk of progression to complete block, so it’s a concern that may require intervention such as pacing.

Understanding how atrial impulses are conducted to the ventricles helps classify second-degree AV block. In this type, some P waves fail to conduct to the ventricles, causing a dropped QRS complex. When you see several P waves in a row followed by a single dropped QRS, with the PR interval remaining the same for the beats that do conduct, that pattern points to Mobitz II.

This contrasts with Wenckebach (Mobitz I), where you’d see a gradual slowing of conduction—the PR interval lengthens progressively until a beat drops. In complete heart block (third degree), there’s no consistent relationship between P waves and QRS complexes at all—the atria and ventricles beat independently. First-degree block shows a single, steadily prolonged PR interval with every P wave still conducting.

Mobitz II is often due to disease in the His-Purkinje system and carries a higher risk of progression to complete block, so it’s a concern that may require intervention such as pacing.