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Cardiac resynchronization therapy (CRT)

Learn how CRT devices can help your heart beat more efficiently and allow your doctor to monitor your health.

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Getting to know your device

Already implanted with a CRT device? Go to the device support page for more information. 

Types of CRT devices

With heart failure, your heart doesn’t pump as well as it should, so your blood fails to supply your body with the oxygen it needs. CRT devices work to help the heart pump properly in a coordinated way. There are two types of CRT devices. One is a special kind of pacemaker called a cardiac resynchronization therapy pacemaker (CRT-P) or “biventricular pacemaker.” The other is the same device but also includes a built-in implantable cardioverter defibrillator (ICD) called a cardiac resynchronization therapy defibrillator (CRT-D). 

Boston Scientific’s CRT device family

Know your device

CRT-P and CRT-D devices help your heart beat more efficiently and monitor your condition, so your doctor can provide the right treatment. A CRT device delivers tiny amounts of electrical energy to the heart. This helps restore the normal timing of the heartbeats, causing both ventricles to pump together more effectively.

Understanding the procedure

Typically, a CRT device is implanted just under the skin in your chest, near your collarbone. The leads are placed in the right atrium, the right ventricle, and on the surface of the left ventricle. Your doctor will discuss with you which side of your chest the device will be implanted prior to your procedure.

Full recovery from surgery can take from several days or weeks to a few months. While you recover, your doctor may ask you to avoid strenuous activity (especially lifting and other activities that use your upper body). Doing so helps ensure the leads have time to firmly attach to your heart tissue. 

After CRT implantation

While you won’t feel any noticeable sensations when your CRT device is monitoring your heart, shock therapy for an arrhythmia may be very noticeable. Before you experience symptoms or receive a shock, talk to your health care team about a plan for contacting your doctor and, if necessary, emergency personnel.


  • Let your family and friends know that in case of an event and you become unconscious to stay with you and call 911
  • If you are conscious but don’t feel well after a shock, have someone call your doctor
  • If you feel fine after a shock and no more symptoms appear, it may not be necessary to seek medical help immediately. However, follow your doctor’s instructions for when to call their office

It’s possible that you could feel symptoms of an arrhythmia but not receive therapy. This depends on the programmed settings of your device. For example, an arrhythmia may cause symptoms, but it may not be fast enough for your device to deliver therapy. In any case, if your symptoms are severe or continue for more than a minute or so, you should seek immediate medical attention.

CRT-D patients report a wide range of experiences as a result of receiving a shock—from a mild thump to a kick in the chest. While the shock may be painful, it will be over in an instant. And while the sensation may be uncomfortable, it means your device is monitoring and responding to dangerous heart rhythm irregularities. The sensation you feel may vary based on the therapy your device delivers.

What to expect from defibrillation:

If your arrhythmia is very irregular and fast, your device can deliver a high-energy shock to stop the arrhythmia and return your heart to its normal rhythm. Many patients faint or become unconscious shortly after a very fast ventricular tachycardia (VT) or ventricular fibrillation (VF) rhythm begins. As a result, many patients do not feel these high-energy shocks. Some say the sudden but brief sensation feels like a kick in the chest. This sensation will only last for a moment. While many find the shock reassuring, other patients may be upset for a short time after the shock is delivered.

Knowing the benefits

While functioning like a normal pacemaker, a CRT-P device delivers small electrical impulses to the left and right ventricles to treat slow heart rhythms.

A CRT-D device can also treat dangerously fast heart rhythms (arrhythmias) that could lead to sudden cardiac arrest.

Explaining the risks

While complications don’t happen very often, it’s important to know that there are risks associated with the implantation of any device or lead. You should talk with your doctor about these risks.

See our patient manuals for detailed safety information.

Learn more about your battery

Like any battery, the energy in your implanted device will naturally decrease over time. The battery’s life is affected both by how much energy is programmed and how often it is required to pace or deliver therapy to your heart. Boston Scientific RESONATETM family CRT-D devices are projected to last 8-15 years1 and VISIONISTTM CRT-P devices are projected to last 7-14 years.2

Boston Scientific’s Resonate HF-CRT-D

Our devices

At Boston Scientific, we are dedicated to advancing heart rhythm management technologies by creating smaller, longer-lasting implants. Download more information about your CRT-P or CRT-D, including device size and longevity.

Resources for you

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Important Safety Information

Cardiac resynchronization therapy pacemakers (CRT-P) and defibrillators (CRT-D) are designed to treat heart failure patients who may or may not have symptoms or who may have symptoms despite the best available drug therapy. They are also designed to help your heart pump more effectively and meet your body’s need for blood flow.  These devices are sensitive to strong electromagnetic interference (EMI) and can be affected by certain sources of electric or magnetic fields. With all medical procedures there are risks associated.  In regard to an implanted ICD, the risks include but are not limited to inappropriate shock, lead moves out of place, loss of stimulation capability, allergic reaction, fluid underneath the skin, and infection.  In rare cases device failure or death can occur.  Be sure to talk with your doctor so that you thoroughly understand all of the risks and benefits associated with the implantation of this system.  To obtain a copy of the device Patient Handbook for more detailed device safety information, go to,  or you can request a copy by calling 1-866-484-3268 or writing to Boston Scientific, 4100 Hamline Ave. N., St. Paul, MN  55112. 

Device Quality and Reliability

It is Boston Scientific’s intent to provide implantable devices of high quality and reliability. However, these devices may exhibit malfunctions that may result in lost or compromised ability to deliver therapy. Refer to Boston Scientific’s CRM product performance report on for more information about device performance, including the types and rates of malfunctions that these devices have experienced historically. While historical data may not be predictive of future device performance, such data can provide important context for understanding the overall reliability of these types of products. Also, it is important that you talk with your doctor about the risks and benefits associated with the implantation of a device.

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