In Junctional Rhythm, what is the primary pacing structure when the SA node is nonfunctional?

In Junctional Rhythm, what is the primary pacing structure when the SA node is nonfunctional?

• A. Ventricles
• B. Bundle of His
• C. AV node
• D. Purkinje fibers

Answer: (C)

In a junctional rhythm, the primary pacing structure takes over when the SA node is nonfunctional. This situation arises when the primary pacemaker of the heart (the SA node) fails to initiate impulses, often due to ischemia, infarction, or other underlying cardiac issues. When this occurs, the AV node becomes the secondary pacemaker. The AV node typically has a slower intrinsic firing rate than the SA node and takes over the pacing responsibilities, usually firing between 40 to 60 beats per minute. The incident of the AV node pacing the heart is characteristic of junctional rhythms, which can manifest as junctional escape rhythms or junctional rhythms with varying degrees of block. This allows the heart to maintain a level of electrical activity and output, preventing complete asystole. It's important to note that while other structures such as the Bundle of His and Purkinje fibers can also serve as pacemakers if the AV node fails, they generally have a lower pacing rate than the AV node and are usually not the primary initiators of rhythm in this context. The Bundle of His and Purkinje fibers become more significant in cases of complete heart block or total AV nodal failure, but they are not typically the first to take over when the

In a junctional rhythm, the primary pacing structure takes over when the SA node is nonfunctional. This situation arises when the primary pacemaker of the heart (the SA node) fails to initiate impulses, often due to ischemia, infarction, or other underlying cardiac issues. When this occurs, the AV node becomes the secondary pacemaker. The AV node typically has a slower intrinsic firing rate than the SA node and takes over the pacing responsibilities, usually firing between 40 to 60 beats per minute.

The incident of the AV node pacing the heart is characteristic of junctional rhythms, which can manifest as junctional escape rhythms or junctional rhythms with varying degrees of block. This allows the heart to maintain a level of electrical activity and output, preventing complete asystole.

It's important to note that while other structures such as the Bundle of His and Purkinje fibers can also serve as pacemakers if the AV node fails, they generally have a lower pacing rate than the AV node and are usually not the primary initiators of rhythm in this context. The Bundle of His and Purkinje fibers become more significant in cases of complete heart block or total AV nodal failure, but they are not typically the first to take over when the