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By Nancy Reid, HealthAtoZ writer
Cardiac resynchronization therapy, or CRT, is a new type of pacemaker used to treat heart failure. It is also called a biventricular pacemaker.
A CRT pacemaker is a more advanced version of a standard pacemaker. While traditional pacemakers simply signal the heart to beat faster, CRT devices signal both sides of the heart, restoring critical timing that improves function.
Like other pacemakers, doctors place the device just under the skin in the upper chest area. Leads, or wires, connect the CRT to the heart. The pocket-watch-sized device gets its power from a long-lasting lithium battery.
How CRT works
Some people with heart failure have problems with the pumping action of their hearts. Specifically, the timing of the two lower chambers is out of sync. A CRT device sends electrical pulses to the heart through the leads. These signals get the heart pumping in time again.
When the heart's pumping action is timed well, it beats more strongly. With each heartbeat, the heart sends more blood to the body. This lessens heart failure symptoms. Some people with heart failure are short of breath and tired much of the time. Studies show that CRT helps people feel better and live more active lives. CRT does not replace heart failure medicines, so people must continue to take them with CRT.
Other therapies for heart failure
Some heart failure patients are also at high risk for fast heartbeats that can cause sudden death. For these people, doctors suggest a device called a cardiac resynchronization therapy defibrillator (CRT-D). This device combines CRT and a defibrillator. It senses when the heart is dangerously fast and sends a shock that returns the heart to a normal pace. Studies show that these devices help people live longer.
The first time you get shocked by a CRT-D, you might wonder who kicked you in the chest. It can be painful, although most people say that, over time, they adjust to the shocks.
Who can use CRT?
CRT may help you if:
- You have moderate to severe heart failure. (Your heart failure has been typed as Class III or IV.)
- You continue to have symptoms of heart failure despite taking optimal drug therapy for it.
- Your heart is not able to pump well, with an ejection fraction of less than or equal to 35 percent. (Ejection fraction is the measurement of the amount of blood pumped from the left ventricle with each heartbeat. Normal would be about 50 percent.)
- You have a certain type of conduction defect.
CRT is only for a specific group of people with heart failure. Your doctor will assess you to see whether CRT will benefit you. As with all medical treatments, the potential benefits need to outweigh the risks.
What are the risks?
Placing a CRT requires surgery and generally takes an hour or two. People often stay in the hospital at least overnight. Like any surgery, this procedure has risks. The chances of problems occurring are small. They include infection, bleeding, damage to the lungs or heart, heart attack and stroke.
The battery in these devices usually lasts from 5 to 7 years. At that time, the whole device is replaced.
This article was reviewed and updated June 2007.
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