Cardiac Resynchronization Therapy (CRT) for Heart Failure

Cardiac resynchronization therapy (CRT) is a treatment for heart failure due to dilated cardiomyopathy. Dilated cardiomyopathy is one type of cardiomyopathy, but not the only one for which CRT is a treatment. The treatment involves a special type of pacemaker that coordinates the timing of the ventricles. CRT can bring about dramatic improvements for some people with heart failure, decreasing the need for hospitalization and lowering the risk of death. Having a pacemaker does come with risks and requires regular upkeep, but in most cases the benefits far outweigh any potential complications and minor inconvenience.

A doctor explaining a model to his patient in the examination room
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How CRT Works

Cardiac resynchronization therapy frequently is used for people with heart failure who have an abnormality in the heart’s electrical conducting system called left bundle branch lock (LBBB) in which the right and left ventricles beat out of sync. A third of people with heart failure have LBBB.

CRT involves the implantation of a special device called a biventricular pacemaker that controls the right and left ventricles of the heart independently. Typical pacemakers control only the right ventricle.

The pacemaker is surgically implanted under the skin. It has two or three leads (insulated wires that deliver electrical impulses) that are attached to the heart and to a tiny battery-powered computer called a generator. The leads are implanted through a vein in the right atrium and right ventricle and into the coronary sinus vein to pace the left ventricle.

The generator is programmed by a healthcare provider to deliver small electrical impulses through the leads to the heart, causing the right and left ventricles to pump together. By appropriately timing the pacing of each ventricle, CRT is able to synchronize the heartbeat, thereby improving the efficiency of the heart and decreasing the amount of work it must do.

People with heart failure who are also at high risk for sudden cardiac death due to dangerously fast heart rhythms may receive a combination pacemaker and implantable cardioverter defibrillator (ICD) device that will deliver a shock to the heart to interrupt a dangerously rapid heartbeat.

How a Biventricular Pacemaker is Implanted

If you are receiving a pacemaker, it will likely be implanted during a three-to-five hour out-patient procedure. You will be awake but given medication to numb the area where the device will be placed and to keep you sleepy and comfortable. An intravenous (IV) line will deliver pain medication, fluids, and antibiotics.

To implant the pacemaker, the healthcare provider will make a small incision just below your left collar bone to create a "pocket" that will hold the wires and computer battery pack. They will place the electronic leads into the large vein that feeds the heart. Special X-rays will be taken to make sure the leads are positioned correctly on each side of the heart.

Once the leads are placed, the healthcare provider will test the CRT with an electric pulse that may make you feel as if your heart is racing. Once the leads are working correctly, they are attached to the pacemaker which is placed under your skin.

Who Should Consider CRT?

CRT is not appropriate for all people with heart failure. The best candidates are those who have:

  • A poor ejection fraction (35% or less). Ejection fraction is a measurement of how much blood the left ventricle of the heart is able to pump out with each beat.
  • An ejection fraction between 36% and 50% accompanied by another indication for a permanent pacemaker, such as heart block (a condition in which the heart's electrical signal slows or stops entirely as it moves from the upper to the lower cardiac chambers)
  • Severe to moderately severe heart failure symptoms
  • Seen no improvement in heart failure symptoms despite medication and lifestyle changes
  • Delayed electrical activation of the heart (such as intraventricular conduction delay or bundle branch block)
  • History of cardiac arrest or are at risk for cardiac arrest

People with heart failure who would not benefit from or need cardiac resynchronization therapy include those who have:

  • Mild heart failure symptoms
  • Diastolic heart failure
  • Heart problems that do not involve dissonance in how the heart chambers beat
  • A reduced ejection fraction but no other symptoms or other indications for pacing
  • A limited life-expectancy due to some non-cardiac condition
  • Limited functional capacity due to a chronic non-cardiac condition

Complications of CRT

Cardiac resynchronization therapy is safe for most people who need it but since it involves placing a foreign object inside the body there are potential—but rare—risks and complications inherent in both the implantation procedure and afterwards.

During Implantation
  • Bleeding

  • Formation of a blood clot

  • Damage to tendons, muscles, or nerves

  • Puncture of a lung or vein

  • Perforation of or tissue damage to the heart

  • Dangerous arrhythmias

  • Heart attack

  • Stroke

After Implantation
  • Infection

  • Deterioration of the skin near the implanted device

  • Movement of the device from the site of implantation or movement of the leads placed in the heart

  • Irritation or damage electrodes may cause to heart tissue and nerves

  • Malfunctioning of the device for any reason

  • Receiving electrical impulses when they are not needed

Living With a Pacemaker

If you are like most patients who undergo CRT, you're likely to feel significantly better and have an improved quality of life once your pacemaker has been implanted. However, you will need to take special care of yourself and the device in order to continue to enjoy these benefits.

  • Have your device checked every three to six months to make sure it is working correctly and has plenty of battery life. Batteries can last up to 10 years but should still be checked. Newer devices have an antenna that communicates with a remote monitor in your home, allowing information from your device to be sent directly to your healthcare provider via the Internet or through a cell phone connection. This reduces the need for frequent office visits.
  • Keep up with regular tests to monitor the function of your heart and device. These tests can include an electrocardiogram (ECG) or echocardiogram (echo). From time to time, your device's settings may need to be adjusted.
  • Carry your device's ID card with you. Show it to other healthcare providers, such as your dentist, you visit as well as to airport security guards. and personnel at other secured areas that have electromagnetic anti-theft systems.
  • Be aware of machines and other devices that may interfere with the function of your pacemaker. Microwave ovens, basic household appliances, computers, TVs and radios are OK.
  • Be careful around electromagnetic anti-theft systems found at store entrances. Walking past one is okay but don't stand still near one or lean against it.
  • Be wary of strong electrical fields. These can be generated by radio transmission towers, heavy-duty electrical equipment, and even the engine of a running car.
  • Don't hold your cell phone too close to your device. Hold it to the ear on the opposite side of your body. When not using your phone, carry it on the side away from your device.
  • Avoid very strong magnets. Older generations of CRT devices cannot be used with MRI scanners, although newer devices can.
  • Be physically active. Get exercise every day but find the happy medium. The right amount of activity should make you feel better, not worse.

A Word From Verywell

If you have heart failure that is limiting your ability to function normally and you are already receiving aggressive medical therapy for heart failure, CRT could be a possible treatment that for you. Most people with pacemakers feel much better afterwards and can go on to lead an active life. Talk with your doctor to determine whether CRT is right for you.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  4. Boston Scientific. How CRTs work.

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Additional Reading

By Richard N. Fogoros, MD
Richard N. Fogoros, MD, is a retired professor of medicine and board-certified in internal medicine, clinical cardiology, and clinical electrophysiology.