What is the intrinsic pacemaking rate of ventricular foci?

What is the intrinsic pacemaking rate of ventricular foci?

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

Answer: (C)

The intrinsic pacemaking rate of ventricular foci is indeed between 20 and 40 beats per minute. Ventricular foci refer to ectopic pacemaker sites located in the ventricles of the heart. These sites can generate impulses independently of the heart's primary pacemaker, the sinoatrial (SA) node, particularly when the normal conduction pathway is impaired or when higher pacemakers, such as the atrioventricular (AV) node, fail.

While higher pacemaking areas like the SA node typically discharge at rates of 60-100 bpm and the AV node generally paces at 40-60 bpm, the ventricular foci operate at a significantly lower intrinsic rate. This slow rate is critical because it serves as a backup mechanism for cardiac function, although it is often inadequate for maintaining effective circulation in cases of higher-level heart block or other conduction disturbances.

Understanding these intrinsic rates helps healthcare providers evaluate and manage cardiac rhythm abnormalities effectively.