What characterizes Mobitz type 2 block?

• A. Progressively increasing PR intervals
• B. Normal consecutive PR intervals followed by non-conduction
• C. Irregular intervals with no consistent pattern
• D. AV junctional escape beats

Answer: (B)

Mobitz type 2 block is characterized by normal consecutive PR intervals followed by a sudden drop of the QRS complex, indicating a failure in conduction from the atria to the ventricles. Unlike Mobitz type 1 (Wenckebach), where there is a gradual lengthening of the PR interval before a dropped beat, Mobitz type 2 maintains a consistent PR interval. This consistent pattern is key to differentiating it from other types of heart blocks. The presence of a dropped beat occurs unpredictably, which can lead to symptoms of bradycardia or decreased cardiac output. Understanding this distinction is crucial in clinical practice, as Mobitz type 2 is often associated with a higher risk of complete heart block, potentially requiring more immediate intervention compared to other types.