Cardiac resynchronization therapy is a procedure to implant a device in your chest to make your 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 your heart (ventricles). The signals trigger your ventricles to contract in a more coordinated way, which improves the pumping of blood out of your heart.

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

Cardiac resynchronization therapy is a treatment for heart failure in people whose ventricles don't contract in a coordinated fashion.

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 your symptoms of heart failure and lower your risk of heart failure complications, including death.

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
• Injury to a blood vessel
• 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

Cardiac resynchronization therapy requires a minor surgical procedure to implant a device in your chest.

You'll likely be awake during the procedure, though the area where the pacemaker is implanted is numbed and you'll receive medication to help you relax (conscious sedation). The procedure typically takes a few hours.

During surgery, insulated wires (leads, or electrodes) are inserted into a major vein under or near your collarbone and guided to your heart with the help of X-ray images. One end of each wire is attached to the appropriate position in your heart. The other end is attached to a pulse generator, which is usually implanted under the skin beneath your collarbone.

Cardiac resynchronization therapy devices include:

• Cardiac resynchronization therapy with a pacemaker (CRT-P). The device used for cardiac resynchronization therapy has three leads that connect the pacemaker to the right upper chamber of your heart (right atria) and both lower chambers (ventricles).
• Cardiac resynchronization therapy with a pacemaker and an ICD (CRT-D). This device may be recommended for people with heart failure who also have a risk of sudden cardiac death. It can detect dangerous heart rhythms and deliver a stronger shock of energy, which is able to reset your heartbeat, than a pacemaker can deliver.

You'll usually stay overnight in the hospital after cardiac resynchronization therapy. Your doctor will test your device to make sure it's programmed correctly before you leave the hospital. Most people can return to their usual activities after a few days.