Cardiac resynchronization therapy (CRT) is a treatment that helps restore a synchronous heart rhythm when your heart has become weak and is no longer beating in a synchronized manner.

CRT involves the use of a pacemaker implanted in the chest.

While CRT can be a life-saving therapy, it isn’t effective for everyone with heart failure or a heart rhythm disturbance called an arrhythmia.

This article will take a closer look at CRT, what it involves, how effective it is, and the potential risks.

A healthy heart beats to a rhythm that allows the heart’s upper chambers (atria) to fill with blood while the lower chambers (ventricles) pump blood out to the body. Once the ventricles are empty, the atria fill them up with blood, and the process starts all over again.

Although the electrical system that keeps your heart going may seem tireless, it’s nevertheless vulnerable to problems, especially when heart failure weakens the pumping strength of the heart muscle.

CRT helps keep the heart beating with a healthier coordinated rhythm in someone with heart failure. The treatment involves the surgical implantation of a small battery-powered CRT pacemaker in the chest.

The device also has thin, flexible wires (known as leads) that extend into the heart muscle itself. The pacemaker sends electrical impulses through the leads and into the heart to stimulate the heart in a pattern that supports a strong and steady rhythm.

There are actually two main types of CRT pacemakers: CRT-P and CRT-D. The right one for you depends on the nature of your heart condition.

CRT-P

A CRT pacemaker (CRT-P) has two primary functions. It delivers electrical impulses to overcome slow, weak heart rhythms, and it sends separate signals to the right and left ventricles to make sure they contract simultaneously.

By doing so, the heart pumps blood to the lungs and the rest of the body more efficiently.

CRT-D

A CRT-D is a pacemaker that also acts as a cardioverter defibrillator, which sends an electric shock to the heart if the device senses an abnormal rhythm. This abnormal rhythm could signal that the person may be going into cardiac arrest.

A 2022 study looked at the use of CRT in people with reduced ejection fraction (HFrEF), a type of heart failure in which the heart’s left side doesn’t pump enough blood to meet the body’s needs. According to this study, CRT-D is associated with a lower mortality risk, but it wasn’t used as often in older adults.

The findings also suggest that CRT-D may be a better option than CRT-P for individuals with severe HFrEF.

A 2017 study suggests that having heart failure puts people at a much higher risk for developing an arrhythmia and that CRT can effectively reduce their mortality risk.

When an arrhythmia develops in someone with heart failure, CRT is considered an appropriate treatment if other options, like medications, aren’t able to maintain a healthy heart rhythm.

Some of the other benefits of CRT include:

  • improved quality of life
  • increased circulation throughout the body
  • lower mortality risk
  • reduced heart failure symptoms, like lightheadedness and fluid retention

Depending on the overall health of the person receiving a CRT device, the procedure may be done on an outpatient basis or as part of an in-patient hospital stay. The process can take 2 to 5 hours.

In the hospital, you’ll recieve medications to help you relax or sleep, but general anesthesia is usually not required.

The doctor then makes a small incision in the chest just under the skin. The device and battery pack are placed in this “pocket,” and then the leads (wires) are placed in veins leading to the heart. When they’re in the right place, the doctor will attach the leads to the CRT and test to make sure everything is working properly.

The doctor will then close the incision. Once you’re fully alert, you’ll be given instructions about living with the CRT and what side effects or complications may occur, as well as what to do if you notice any problems.

Aside from limiting strenuous activities for the first several weeks and making sure the incision stays clean while it heals, you should be able to follow your regular diet, work, and otherwise carry on with your everyday activities.

CRT is most effective in individuals with heart failure when treatment begins earlier in the disease progression.

Patients with the greatest chance of responding well to CRT typically have:

Additionally, CRT is not effective for everyone with heart failure. About 30 percent of heart failure patients don’t respond to CRT, and in some cases, patients may be considered “negative responders” and require the device to be deactivated.

A 2019 study suggests that CRT was effective in keeping individuals alive and out of the hospital with heart failure complications in about 50 percent of people under the age of 75. And for individuals 75 years old or older, the 1-year survival rate was 47 percent.

In that same study, complications occurred in just 19 percent of people with heart failure and CRT pacemakers.

It’s worth noting that people with heart failure often have other health problems that cannot be addressed by CRT, like kidney damage or liver disease. So while CRT may be working effectively, a person with heart failure may still have to deal with several other health complications.

In general, the surgery to implant a CRT pacemaker and the subsequent therapy are safe and well-tolerated.

But as with any medical procedure and long-term treatment, there are some risks associated with CRT, like:

  • additional arrhythmias
  • bleeding
  • infection
  • mechanical difficulties with the CRT pacemaker or leads
  • swelling in the area of the chest housing the device

For people with heart failure and arrhythmia, cardiac resynchronization therapy (CRT) can be a life-saving treatment and improve day-to-day living.

The therapy, which is usually prescribed once other treatment options have proved ineffective, can often ease heart failure symptoms and prolong a person’s life.

The key, once you have a CRT pacemaker, is to keep up with your cardiologist appointments. This is important to help ensure that the device is working properly and to spot signs that it may need to be replaced well before there are any problems.