What can replace the SA node to keep heart rhythm constant?

• A. A defibrillator to restart the heart
• B. An artificial valve implant
• C. A heart transplant
• D. A pacemaker to keep heart rhythm constant

Answer: (D)

The heart’s rhythm is controlled by electrical activity started by the sinoatrial (SA) node, the natural pacemaker that sets the pace of each beat. When the SA node isn’t reliable, a pacemaker can be implanted to take over that pacing role, sending regular electrical impulses to trigger heartbeats and keep the rhythm steady. Pacemakers can be adjusted to match normal resting rates and can respond to activity, which is exactly what’s needed to maintain a constant rhythm over time.

A defibrillator, by contrast, is designed to shock the heart back into a normal rhythm during dangerous fast or chaotic rhythms, not to provide continuous pacing. An artificial valve changes blood flow through the heart, not the timing of beats. A heart transplant replaces the whole heart rather than specifically maintaining a constant rhythm through electrical pacing.