How pacemakers work

Summary

Implantable pacemakers and defibrillators are devices that use electrical shocks to regulate the heart's rhythm, with advancements in technology increasing the number of implantations each year. These devices can help treat various heart conditions, including those where the sinoatrial node fails to function properly. While pacemakers rely on electrodes placed in the heart’s chambers, more advanced devices like the implantable defibrillator (ICD) and CRT ICD can deliver life-saving shocks. Efforts are ongoing to develop leadless and wireless pacemakers, offering the potential for safer and more effective heart treatments without the risks associated with traditional lead-based systems.

Takeaways

• 😀 Implantable pacemakers and defibrillators apply electric shocks to regulate heart rhythm and restart it if necessary.
• 😀 The number of pacemaker and defibrillator implants is increasing steadily, now exceeding half a million per year.
• 😀 The heart consists of four chambers: two atria and two ventricles, which work in coordination to pump blood.
• 😀 Electrical impulses from the sinoatrial node regulate the beating of a healthy heart by coordinating contractions of the chambers.
• 😀 When the sinoatrial node fails, an artificial pacemaker can regulate the heartbeat with small, evenly timed electric shocks.
• 😀 Implantable defibrillators (ICDs) can sense a stopped heart and deliver powerful shocks to restart it.
• 😀 CRT ICDs are a more advanced device that helps resynchronize the ventricles using a third lead inserted into the left ventricle.
• 😀 Leads used in pacemakers and defibrillators can cause complications, with a 20% chance of lead failure in ICD patients within 10 years.
• 😀 Replacing leads may require open-heart surgery in 2% of cases.
• 😀 New developments in pacemaker technology aim to eliminate the need for leads, such as subcutaneous ICDs and wireless designs.

Q & A

What are implantable pacemakers and defibrillators used for?

Implantable pacemakers and defibrillators are devices designed to apply electric shocks to maintain the heart's rhythm and, if necessary, restart it.

How does the technology related to pacemakers and defibrillators improve over time?

As technology improves, the list of treatable conditions grows, and the number of devices implanted steadily increases, now exceeding half a million per year.

What are the four chambers of the heart and their roles?

The heart is made up of two atria and two ventricles. The atria receive blood and pump it into the ventricles, which then contract to pump blood to the lungs and the rest of the body.

How does the electrical conduction system regulate the heartbeat?

The heart's rhythm is regulated by electrical impulses. These begin at the sinoatrial (SA) node, which causes the atria to contract, and then the signal travels to the atrioventricular (AV) node and through the Purkinje fibers, causing the ventricles to contract.

What happens when the sinoatrial node fails?

If the sinoatrial node fails to function properly, an artificial pacemaker can be implanted to regulate the heartbeat with small, evenly timed electrical shocks.

What is the difference between a pacemaker and an implantable defibrillator (ICD)?

A pacemaker regulates the heartbeat with small electrical shocks, while an implantable defibrillator (ICD) can sense a stopped heart and deliver a powerful shock to restart it.

What is a CRT ICD, and how does it work?

A CRT ICD is a more sophisticated device that uses a third lead inserted into the left ventricle to resynchronize the ventricles when necessary.

What are the potential complications associated with implanted leads in pacemakers and ICDs?

One of the risks is lead failure, which occurs in about 20% of ICD patients within 10 years. In some cases, lead replacement requires open-heart surgery.

Why are efforts being made to develop new pacemakers without leads inside the heart?

There is a need for pacemakers that do not depend on leads inside the heart due to the complications and risks associated with lead failure and the need for replacements.

What are some new designs for pacemakers that avoid the use of leads?

One design, the subcutaneous ICD, places the lead just outside the heart, under the skin. Additionally, wireless designs are being developed to eliminate the need for leads altogether.