What is the ventricular rate in a third degree AV block with a junctional focus?

What is the ventricular rate in a third degree AV block with a junctional focus?

• A. 40-60 bpm
• B. 60-100 bpm
• C. 20-40 bpm
• D. 80-120 bpm

Answer: (A)

In a third-degree AV block, also known as complete heart block, there is a lack of communication between the atria and the ventricles. As a result, the atrial rhythm and the ventricular rhythm operate independently of one another. In cases where there is a junctional focus responsible for ventricular pacing, the ventricular rate typically ranges between 40-60 beats per minute. This is because the junctional escape rhythm arises from the area around the AV node or bundle of His, which typically fires at this slower rate due to its intrinsic pacing characteristics.

Understanding this ventricular rate is crucial for diagnosing and managing patients with third-degree AV block, as the rate can significantly influence hemodynamics and the clinical presentation. Other rates listed in the choices, such as 60-100 bpm and 80-120 bpm, are more characteristic of junctional rhythms with higher rates or atrial pacing, which do not apply in this situation. The range of 20-40 bpm would indicate a slower escape rhythm possibly from the ventricles themselves, which is not typically the case in this scenario since a junctional focus is pacing the ventricles.