How Cardiac Resynchronization Therapy Treats Heart Failure

Cardiac resynchronization therapy (CRT) is a treatment that involves a special type of pacemaker that coordinates contractions of the heart's ventricles. It's recommended for some heart failure patients who have developed arrhythmia, an irregular heart rhythm.

CRT can bring about dramatic improvements for some people with heart failure, decreasing the need for hospitalization and lowering the risk of death.

How CRT Works

Cardiac resynchronization therapy is frequently used for people with heart failure who have an abnormality in the heart’s electrical conducting system. A common abnormality is a 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.

The CRT device 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. This improves the efficiency of the heart and decreases the amount of work it must do.

Types of Devices

CRT can involve two different devices:

• Biventricular pacemaker: This device is implanted to control the right and left ventricles of the heart independently. (In contrast, a typical pacemaker controls only the right ventricle.)
• Defibrillator: A combination pacemaker and implantable cardioverter defibrillator (ICD) is recommended for heart failure patients at high risk for sudden cardiac death due to dangerously fast heart rhythms. This device will deliver a shock to the heart to interrupt a dangerously rapid heartbeat.

Benefits

CRT has been found to improve the heart's efficiency and increase blood flow. This helps to relieve heart failure symptoms, like shortness of breath.

In addition, clinical studies have found decreases in hospitalization and improved quality of life, including better tolerance for exercise.

Implantation

The pacemaker or implantable cardioverter-defibrillator (ICD) will likely be implanted during an outpatient procedure taking about three to five hours.

Your healthcare provider will give you medicine to either make you sleepy or fall asleep. You'll be given medication to numb the area where the device will be placed. An intravenous (IV) line will deliver pain medication, fluids, and antibiotics.

To implant the device, the healthcare provider will make a small incision just below your left collarbone 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 are then 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.

The incision will be closed with staples or stitches. You'll then be moved to recovery to wait until the anesthesia wears off. You may need to stay in the hospital overnight so your healthcare provider can monitor the device and adjust settings.

Who Is a Candidate?

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
• 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

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

Living With a Pacemaker

If you are like most patients who undergo CRT, you'll likely 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 to continue to enjoy these benefits:

• Check battery life: 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.
• Get tested regularly: 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 you visit, such as your dentist, as well as to airport security guards. and personnel at other secured areas that have electromagnetic anti-theft systems.
• Beware of interference: Look out for 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: These can be 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.

Summary

Cardiac resynchronization therapy is a treatment for heart failure patients with arrhythmia. It is a special pacemaker inserted under the skin that allows the right and left ventricles to pump together. The pacemaker can also include a defibrillator for patients at high risk of sudden cardiac death.

CRT helps to improve the heart's efficiency and relieve symptoms of heart failure. However, it isn't appropriate for all patients with heart failure. Your healthcare provider will work with you to determine the best treatment.