In a third degree AV block, what is the heart rate range for a ventricular focus pacing?

In a third degree AV block, what is the heart rate range for a ventricular focus pacing?

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

Answer: (C)

In a third-degree AV block, also known as complete heart block, the atrial impulses do not conduct to the ventricles. This results in disassociation between atrial and ventricular activity. The heart relies on a junctional or ventricular focus to maintain a heart rhythm.

In the case of ventricular pacing during a complete heart block, the intrinsic ventricular rate typically ranges from 20 to 40 beats per minute. This is due to the fact that if the signals from the atria do not reach the ventricles, the ventricles will initiate their own pacing through the Purkinje fibers or other junctional pacemaker cells. This intrinsic rate is much slower than the normal sinus rhythm, which can lead to symptoms of bradycardia. Therefore, recognizing that a ventricular focus pacing occurs at this rate range is crucial for understanding the implications of a third-degree AV block.