Second Degree Heart Block Type II is best described as an AV block with fixed PR intervals and intermittent nonconducted QRS complexes. Which option matches this description?

Second Degree Heart Block Type II is best described as an AV block with fixed PR intervals and intermittent nonconducted QRS complexes. Which option matches this description?

• A. Progressive PR prolongation with dropped beats
• B. Fixed PR interval with intermittent nonconducted QRS
• C. Complete AV dissociation
• D. Irregular rhythm with no dropped beats

Answer: (B)

Second-degree AV block type II, also known as Mobitz II, is defined by a fixed PR interval for conducted beats with occasional nonconducted P waves that fail to produce a QRS, causing dropped beats. This pattern reflects a block in the His-Purkinje system and differs from Mobitz I, where the PR interval progressively lengthens before a drop, and from complete AV block, which shows AV dissociation with no consistent relationship between P waves and QRS. An irregular rhythm without dropped beats does not show these intermittent nonconducted P waves. Therefore, the description of a constant PR interval with intermittent nonconducted QRS matches Mobitz II.

Second-degree AV block type II, also known as Mobitz II, is defined by a fixed PR interval for conducted beats with occasional nonconducted P waves that fail to produce a QRS, causing dropped beats. This pattern reflects a block in the His-Purkinje system and differs from Mobitz I, where the PR interval progressively lengthens before a drop, and from complete AV block, which shows AV dissociation with no consistent relationship between P waves and QRS. An irregular rhythm without dropped beats does not show these intermittent nonconducted P waves. Therefore, the description of a constant PR interval with intermittent nonconducted QRS matches Mobitz II.