What is Cardiac Resynchronization Therapy?

Millions of people worldwide suffer from con­gestive heart failure (CHF), a serious and common problem that is often due to weak pumping of the heart muscle. Poor heart pumping function can cause fatigue, leg swelling, trouble exercising, and difficulty breathing.  Lifestyle changes, medications, and heart sur­gery can sometimes help with symptoms, but because many people with CHF also have an arrhythmia, or heart rhythm problem, they need even more help to keep their hearts functioning properly.

Cardiac Resynchronization Therapy (CRT) can relieve CHF symptoms by improving the timing of the heart’s contractions, or beats, which protects patients from abnormally slow and fast heart rhythms. While not all patients will qualify for or benefit from CRT, some patients may have features visible on their electrocardiogram (ECG or EKG) indicating that they may improve with CRT.

CRT uses a biventricular pacemaker (or defibrillator) with two wires in the lower chambers of the heart to overcome this slow or abnormal conduction. By delivering simultaneous or near simultaneous electrical impulses to both lower heart chambers (the right and left ventricles), it causes the heart to beat in a more synchronized, efficient manner. Biventricular pacing improves the symptoms of about two-thirds of the patients undergoing this procedure and also improves survival.

As people with heart muscle damage also may have dangerously fast heart rhythms, biventricular pacing is often combined with a defibrillator.

How does a CRT device work?

The procedure to put in a resynchronization device is a little more complicated than putting in a regular pacemaker or defibrillator. The extra or third wire required is usually positioned in a very small vein that goes to the left side of the heart. Although most people have a vein that can be used for this purpose, this is not true of everyone. Therefore, occasionally this extra wire is placed on the outside of the heart during a surgical procedure or at the time of another heart operation such as valve surgery or a coronary bypass operation.

Like all pacemakers and defibrillators, biventricular devices require monitoring to be certain that they are functioning in the best possible way. Their batteries also gradually wear down, and they need to be changed – generally a small operation – every 5-7 years.