How do pacemakers work?

A healthy heart beats fast enough to deliver a constant supply of blood to the body.

Some heart diseases mean that the heart beats too slowly. That is called a brachycardia heart rhythm disorder. Examples of this include AV block or sick sinus syndrome (a damaged sinus node).

Sometimes pacemakers are only needed for a short period of time, like if the heart beats too slowly during an operation or in an emergency. An external pacemaker device is then used. Like with a catheter, the electrodes are inserted into a larger vein in the neck, arm or groin and pushed through to the heart.

But external pacemakers can also send signals to the heart along other paths:

• Via the chest wall: The signals are sent to the heart from outside through the chest wall. The pacemaker electrodes are stuck or pressed onto the skin.
• Via the food pipe: An electrode is inserted into the food pipe until it is behind the heart.
• Via the epicardium (outer skin of the heart): The electrodes can be placed directly on the heart during surgery.

These methods are quite involved, but are not painful because a general anesthetic is used.

If the heart needs constant support from a pacemaker, a minor procedure is used to implant the device into the body. The disc-shaped pacemaker is about 5 centimeters (about 2 inches) in diameter and it is inserted beneath the skin below the collar bone and then sewn into place. It is sometimes implanted beneath the chest muscle instead. This can be done if there more space is needed, which may be necessary in younger children, for instance. One or more wires (leads) extend from the device to the electrodes, depending on the type of pacemaker. The leads are typically fed into a larger vein and then pushed through to the heart.

The pacemaker uses batteries as a power source for transmitting the electrical signals. The batteries last for about 10 to 14 years, and then the pacemaker has to be replaced.

Modern pacemakers offer other functions besides sending electrical signals. For instance, they can monitor whether the wearer is exercising or being physically active. The pacemaker increases the speed of the signals because the heart then needs to beat faster. It can also record and save the heart’s activity as an ECG curve. The data can be analyzed during a pacemaker check. Some devices can also send the data to your doctor on a daily basis.

• Single-chamber pacemaker: The electrical impulses are sent to the heart via one electrode. It ends either in the right atrium or at the tip of the right ventricle. Single-chamber pacemakers are suitable if the heart’s sinus node is diseased and can no longer generate any impulses.
• Dual-chamber pacemaker: In these devices, two electrodes send impulses to the heart, one stimulating the right atrium, the other the right ventricle. These devices are typically used to treat AV block.
• Triple-chamber pacemaker: These more rarely used pacemakers have an additional third electrode which feeds into the left ventricle via a coronary vein. They can be an option if the heart muscle is severely weakened. The device tries to ensure that the ventricles contract as harmoniously as possible again. Experts call that cardiac resynchronization therapy.

Complications during the implantation and use of a pacemaker are rare. The following complications are possible:

• Infections
• Wound healing problems
• Bleeding if blood vessels or heart tissue are damaged
• Damage to the lungs
• Slipped or damaged electrodes
• Device malfunctions

Some types of pacemakers can cause what is known as pacemaker syndrome. That is where the atria and ventricles are not perfectly in sync with one another, and it may cause problems such as a pounding heart (palpitations) or dizziness.

It is usually possible to live a relatively normal daily life with a pacemaker. But there are certain things you should know:

• Make a note of your next check-up appointment and be sure to go in.
• Always have your pacemaker ID card with you so that in an emergency situation paramedics know right away that you have a pacemaker.
• Some medical devices can interfere with pacemakers. For instance, MRI scans can pose a risk for some pacemakers, but not for others. Your doctor will advise you about which examinations and treatments are possible.
• Read the instruction manual before buying larger household appliances and check if there are any special warnings. You might need to keep a distance of about 25 cm (about 9 inches) from induction stoves, for example. But that shouldn’t interfere with cooking.
• Talking or listening to music on your cell phone won’t affect the functioning of a pacemaker. But do not press pones or headphone directly against the body where the pacemaker is implanted. And always keep a distance of at least 10 centimeters (about 4 inches) between inductive charging stations and your pacemaker.
• Tell security staff at airports (or in other places with similar scanners such as department stores, museums or courts) that you have a pacemaker and show them your pacemaker ID if necessary. You will then be frisked or checked using a metal detector to make sure that no alarms are set off unnecessarily and your pacemaker is not affected.
• Keep an eye out for warning signs in unfamiliar surroundings: Rooms or areas that you shouldn’t enter if you have a pacemaker usually have a warning sign.

Like pacemakers, defibrillators can also be implanted (ICD = implantable cardioverter-defibrillator). These two devices look similar, but they have different jobs:

• A pacemaker is implanted if the heart is beating too slowly on its own. It regularly transmits weak signals in the rhythm of a normal pulse. Each of these signals triggers a single heartbeat.
• Defibrillators are implanted if the heart is beating too quickly some of the time. It transmits stronger electrical signals. That makes the heart stop for a brief moment so that it can beat in its normal rhythm again afterwards. All defibrillators also have a pacemaker function.