Pacemaker

A pacemaker is a small device that's placed (implanted) in the chest to help control the heartbeat. It's used to prevent the heart from beating too slowly. Implanting a pacemaker in the chest requires a surgical procedure

A pacemaker is also called a cardiac pacing device.

Types

Depending on your condition, you might have one of the following types of pacemakers.

• Single chamber pacemaker. This type usually carries electrical impulses to the right ventricle of your heart.
• Dual chamber pacemaker. This type carries electrical impulses to the right ventricle and the right atrium of your heart to help control the timing of contractions between the two chambers.
• Biventricular pacemaker. Biventricular pacing, also called cardiac resynchronization therapy, is for people who have heart failure and heartbeat problems. This type of pacemaker stimulates both of the lower heart chambers (the right and left ventricles) to make the heart beat more efficiently.

Why it's done

A pacemaker is implanted to help control your heartbeat. Your doctor may recommend a temporary pacemaker when you have a slow heartbeat (bradycardia) after a heart attack, surgery or medication overdose but your heartbeat is otherwise expected to recover. A pacemaker may be implanted permanently to correct a chronic slow or irregular heartbeat or to help treat heart failure.

What a pacemaker does

Pacemakers work only when needed. If your heartbeat is too slow (bradycardia), the pacemaker sends electrical signals to your heart to correct the beat. Some newer pacemakers also have sensors that detect body motion or breathing rate and signal the devices to increase heart rate during exercise, as needed.

A pacemaker has two parts:

• Pulse generator. This small metal container houses a battery and the electrical circuitry that controls the rate of electrical pulses sent to the heart.
• Leads (electrodes). One to three flexible, insulated wires are each placed in one or more chambers of the heart and deliver the electrical pulses to adjust the heart rate. However, some newer pacemakers don't require leads. These devices, called leadless pacemakers, are implanted directly into the heart muscle.

Cardiac Resynchronization Therapy

Cardiac resynchronization therapy is a procedure to implant a device in the chest to make the heart's chambers squeeze (contract) in a more organized and efficient way.

Cardiac resynchronization therapy (CRT) uses a device called a biventricular pacemaker — also called a cardiac resynchronization device — that sends electrical signals to both lower chambers of the heart (right and left ventricles). The signals trigger the ventricles to contract in a more coordinated way, which improves the pumping of blood out of the heart.

Sometimes the device also contains an implantable cardioverter-defibrillator (ICD), which can deliver an electrical shock to reset the heartbeat if the heart rhythm becomes dangerously irregular.

Why it's done

Cardiac resynchronization therapy is a treatment for heart failure in people whose lower heart chambers (ventricles) don't contract in a coordinated fashion. It's frequently used for people who have heart failure and a condition called left bundle branch block or for people who are likely to require cardiac pacing due to low heart rates.

If you have heart failure, your heart muscle is weakened and may not be able to pump out enough blood to support your body. This can be worsened if your heart's chambers aren't in sync with each other.

Cardiac resynchronization therapy may reduce symptoms of heart failure and lower the risk of heart failure complications, including death.

Risks

All medical procedures come with some type of risk. The specific risks of cardiac resynchronization therapy depend on the type of implant and your overall health.

Complications related to cardiac resynchronization therapy and the implantation procedure may include:

• Infection
• Bleeding
• Collapsed lung (pneumothorax)
• Compression of the heart due to fluid buildup in the sac surrounding the heart (cardiac tamponade)
• Failure of the device
• Shifting of device parts, which could require another procedure

Implantable cardioverter-defibrillators (ICDs)

An implantable cardioverter-defibrillator (ICD) is a small battery-powered device placed in the chest to detect and stop irregular heartbeats (arrhythmias). An ICD continuously monitors the heartbeat and delivers electric shocks, when needed, to restore a regular heart rhythm.

You might need an ICD if you have a dangerously fast heartbeat that keeps your heart from supplying enough blood to the rest of your body (such as ventricular tachycardia or ventricular fibrillation) or if you are at high risk of such a heart rhythm problem (arrhythmia), usually because of a weak heart muscle.

An ICD differs from a pacemaker — an implantable device that can prevent dangerously slow heartbeats.

Types

An ICD is a type of cardiac therapy device. There are two basic types:

• A traditional ICD is implanted in the chest, and the wires (leads) attach to the heart. The implant procedure requires invasive surgery.
• A subcutaneous ICD (S-ICD) is another option that's implanted under the skin at the side of the chest below the armpit. It's attached to an electrode that runs along the breastbone. An S-ICD is larger than a traditional ICD but doesn't attach to the heart.

Risks

Possible risks of having an ICD implanted include:

• Infection at the implant site
• Swelling, bleeding or bruising
• Blood vessel damage from ICD leads
• Bleeding around the heart, which can be life-threatening
• Blood leaking through the heart valve (regurgitation) where the ICD lead is placed
• Collapsed lung (pneumothorax)
• Movement (shifting) of the device or leads, which could lead to cardiac perforation (rare)