Cardiac Medicine Certification (CMC) Practice Exam

What is the main risk associated with Type II 2nd degree AV block (Mobitz Type II)?

1. It can progress to ventricular fibrillation.

2. It can develop into third-degree heart block without warning.

3. It usually resolves spontaneously without treatment.

4. It is never symptomatic for the patient.

The correct answer is: It can develop into third-degree heart block without warning.

The primary risk associated with Type II 2nd degree AV block, also known as Mobitz Type II, is indeed its potential to progress to third-degree heart block without warning. This type of block demonstrates a consistent pattern of dropped beats, with some impulses being conducted normally and others being blocked at the AV node. This unpredictability in the progression to a complete block is particularly concerning because, unlike Mobitz Type I, which shows a gradual increase in the PR interval before a dropped beat, Mobitz Type II does not exhibit this warning. The occurrence can be sudden and leads to a complete loss of ventricular rate, which can have serious clinical implications, including severe bradycardia or even asystole. This presents a risk of significant hemodynamic instability and can result in syncope or other complications. The other options do not accurately represent the characteristics or risks associated with Mobitz Type II. Whereas ventricular fibrillation is more commonly associated with other arrhythmias, spontaneous resolution is less likely in this case and symptoms can still occur, as some patients may experience symptoms related to decreased cardiac output, particularly if there is associated bradycardia.