In heart transplant patients with two SA nodes, which node acts as the dominant pacemaker?

In heart transplant patients with two SA nodes, which node acts as the dominant pacemaker?

• A. The patient’s own SA node
• B. The transplanted heart's SA node
• C. Both SA nodes
• D. None of the SA nodes

Answer: (B)

In the context of heart transplant patients, the transplanted heart's SA node typically assumes the role of the dominant pacemaker. After transplantation, the recipient's own SA node is disconnected from the controlling autonomic nervous system, as it is no longer connected to the rest of the body. This disconnection means that it cannot contribute to the heart's electrical activity effectively.

The newly transplanted heart is innervated and comes with its own functioning SA node that is capable of generating electrical impulses to initiate heartbeats. Therefore, this node becomes the primary source for maintaining heart rhythm. Even though both nodes exist, the transplanted SA node has the physiological advantage in terms of controlling heart rate because of its intact connection to the heart’s conduction system in its new environment.

In summary, the transplanted SA node becomes the dominant pacemaker as it is equipped to take over the rhythm of the heart, while the original SA node remains ineffective post-transplant.