What is the ventricular rate characteristic of complete (third-degree) AV block?

What is the ventricular rate characteristic of complete (third-degree) AV block?

• A. 60-100 beats per minute
• B. 40-60 beats per minute
• C. 100-120 beats per minute
• D. 80-90 beats per minute

Answer: (B)

In complete (third-degree) AV block, the atrial and ventricular rates become dissociated due to the failure of electrical impulses to pass from the atria to the ventricles. This condition often results in a ventricular escape rhythm, which typically falls within the range of 40-60 beats per minute. The escape rhythm is a compensatory mechanism that allows the ventricles to continue beating independently of the atrial activity, but at a slower pace than normal sinus rhythm. Because the intrinsic pacing of the ventricles is primarily driven by the bundle of His or Purkinje fibers after the blockage, this results in a ventricular rate on the lower end of the spectrum. The typical range for these escape rhythms accounts for bradycardia and reflects the heart's attempt to maintain a minimum level of circulation until a more effective pacing mechanism can be restored.

In complete (third-degree) AV block, the atrial and ventricular rates become dissociated due to the failure of electrical impulses to pass from the atria to the ventricles. This condition often results in a ventricular escape rhythm, which typically falls within the range of 40-60 beats per minute. The escape rhythm is a compensatory mechanism that allows the ventricles to continue beating independently of the atrial activity, but at a slower pace than normal sinus rhythm.

Because the intrinsic pacing of the ventricles is primarily driven by the bundle of His or Purkinje fibers after the blockage, this results in a ventricular rate on the lower end of the spectrum. The typical range for these escape rhythms accounts for bradycardia and reflects the heart's attempt to maintain a minimum level of circulation until a more effective pacing mechanism can be restored.