Cardiac Resynchronization Therapy
Heart failure is a common and serious medical condition. Despite its misleading name, "heart failure" does not mean your heart suddenly stops working. Instead, heart failure develops slowly over time as your heart muscle gradually weakens. The "failure" refers to your heart's inability to pump enough blood to meet your body's needs.
All people with heart failure have one thing in common: their hearts do not pump as well as they should, and so blood does not circulate as well as it should. Your body needs that blood to live and work.
To better understand heart failure, it is helpful to understand the heart. Visit Heart and Blood Vessel Basics to see what a healthy heart looks like and how it works.
What is cardiac resynchronization therapy (CRT)?
Cardiac resynchronization therapy (CRT) is one treatment option for some heart failure patients. CRT uses electrical impulses to help your heart pump more effectively.
In a healthy heart, the chambers contract and relax in a coordinated way, or in synchrony. Heart failure can cause problems with the timing or coordination of your heart's contractions - especially in the ventricles (lower chambers). In other words, it can cause dyssynchrony. When your heart's contractions are not coordinated, your heart may not deliver enough blood to your body. Without enough blood, important organs like your brain and kidneys cannot function properly.
A CRT device can help restore normal coordination, or synchrony. The device uses leads (insulated wires threaded into the heart) to deliver small electrical impulses to the ventricles. The impulses help your ventricles contract at the same time, or "resynchronize." When your ventricles pump together, your heart can work more efficiently to help your body get the blood it needs to live and work.
CRT is sometimes called "biventricular pacing." And a CRT device is sometimes called a biventricular pacemaker or a cardiac resynchronization therapy pacemaker (CRT-P).
How is cardiac resynchronization therapy different from cardiac resynchronization with defibrillation therapy?
CRT is used to treat heart failure. Some heart failure patients are also at high risk for sudden cardiac death. These patients may benefit from CRT with defibrillation therapy. A CRT device that also provides defibrillation therapy is called a cardiac resynchronization therapy defibrillator (CRT-D).
Sudden cardiac death begins when the heart develops a dangerously fast rhythm called ventricular fibrillation. The heart's contractions become so fast and chaotic that the heart cannot pump blood to the body. If not treated immediately, death occurs in a few minutes.
In addition to treating heart failure, a CRT-D detects and treats those dangerously fast heart rhythms that can lead to sudden cardiac death. The device continuously monitors the heart's rhythm. If a dangerous rhythm appears, the CRT-D delivers a shock to stop the fast rhythm and return the heart to a normal rhythm.
Does cardiac resynchronization therapy replace medications?
Probably not. However, your doctor may reduce or change your medications after implanting a CRT device. Your doctor will determine the best therapy for you, which often includes both medication and a CRT device.
What are the benefits of cardiac resynchronization therapy?
Benefits of CRT for heart failure patients may include:
- More energy to participate in everyday activities
- Relief from symptoms, such as shortness of breath
- Improvement in the New York Heart Association (NYHA) heart failure classification
Should everyone with heart failure have a cardiac resynchronization therapy device?
No. Not everyone with heart failure will benefit from CRT. In general, patients who are good candidates for a CRT device are those with:
- Moderate to severe heart failure symptoms (for example, difficulty breathing or extreme tiredness), despite other therapy
- A weakened and enlarged heart
- An electrical problem that causes uncoordinated pumping of the ventricles (Learn more about the heart's electrical system.)
Patients who respond favorably to other treatments, such as lifestyle changes and medication, may not need a CRT device.
What are the parts of a cardiac resynchronization therapy system?
A CRT system has two parts:
- Device - The device is quite small, and easily fits in the palm of your hand. It contains small computerized parts that run on a battery.
- Leads - The leads are insulated wires that connect the device to your heart. The leads carry electrical signals both to and from your heart:
The leads carry your heart's electrical signals from your heart to the device so that the device can monitor your heart rhythm.
The leads also deliver electrical impulses from the device to your heart for therapy.
How is a cardiac resynchronization therapy system implanted?
The implant of a CRT system requires surgery in a hospital. Through a small incision in your chest, your doctor implants the device under the skin near your collarbone. The device is connected to leads, which are threaded through blood vessels and placed in your heart.
What are the risks associated with implantation of a cardiac resynchronization therapy system?
Some of the risks that may occur after the device is implanted include:
- The leads may move out of place in the heart.
- The leads or electrical impulses may irritate or damage the surrounding tissues, including heart tissue and nerves.
- The device might not detect or appropriately treat your heart rhythms.
These risks are rare. If you have further questions about the risks and benefits associated with CRT, be sure to talk with your doctor.
What does the therapy feel like?
Your doctor will program your CRT device to treat your specific heart condition. Depending on your specific device and how it is programmed, you may receive heart failure therapy, pacing therapy, and/or defibrillation therapy:
- Heart failure therapy - Heart failure therapy helps your ventricles contract in a coordinated way. Most patients do not feel the low-energy electrical impulses delivered with the heart failure therapy.
- Pacing therapy - Pacing therapy treats heart rhythms that are too slow. Most patients do not feel the low-energy electrical impulses delivered with the pacing therapy.
- Defibrillation therapy (CRT-D only) - Defibrillation therapy treats dangerously fast heart rhythms. When a CRT-D shocks the heart back to normal rhythm, it uses higher energy. The shock gives a feeling that has been described as a "kick in the chest." Many patients are unconscious when the shock is delivered and don't remember the shock at all. The shock comes quickly and lasts less than a second.
What is life like with a cardiac resynchronization therapy system?
In general, there are few activities that are "off-limits" to patients because they have a CRT device. Your CRT device will help you enjoy as active and productive a lifestyle as your overall health permits. People who receive CRT devices often report fewer symptoms, more energy, and a higher quality of life after the device implant.
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