What is a characteristic of the original SA node in heart transplant patients?

What is a characteristic of the original SA node in heart transplant patients?

• A. It completely stops functioning
• B. It continues to send signals
• C. It takes over as the dominant pacemaker
• D. It functions independently from the transplanted heart

Answer: (B)

In heart transplant patients, the original SA (sinoatrial) node typically continues to send signals, even though its function can be altered. When a heart is transplanted, the new heart is often denervated, meaning it lacks direct neural connections from the autonomic nervous system. This can affect the rate at which the SA node fires, but it does not entirely stop functioning.

The SA node remains capable of generating electrical impulses, which can potentially influence the heartbeat. However, the dominant pacemaking activity in a transplanted heart usually comes from the donor heart's own SA node or whatever pacemaking mechanisms are effective in response to the new physiological conditions. As a result, while the original SA node may still be active, its significance is largely diminished in favor of the transplanted heart's pacemaking activity.

This understanding helps clarify that while the original SA node is not completely inert, its role becomes secondary as the body adapts to the new heart.