Cardiac resynchronization therapy (CRT) is a procedure to implant a device in your chest to make your heart’s chambers contract in a more organized and efficient way. It is a treatment for heart failure in people whose ventricles don’t contract at the same time or in an “asynchronous” fashion, hence the term Cardiac Resynchronization Therapy or CRT.

Courtesy of St. Jude

CRT uses a biventricular pacemaker (or defibrillator) with two wires in the lower chambers of the heart that delivers electrical signals to both of the lower chambers of your heart (the right and left ventricles). The signals tell your ventricles to contract at the same time, maximizing the amount of blood that’s pumped out of your heart. Sometimes the device also contains an implantable cardioverter-defibrillator (ICD), which can deliver stronger electrical shocks if your heart rhythm becomes dangerously erratic.

Cardiac resynchronization therapy delivers electrical signals that cause your heart to beat in a way that may reduce your symptoms of heart failure and reduce your risk of heart failure complications, including death. Biventricular pacing improves the symptoms of about two-thirds of the patients undergoing this procedure and also improves survival.

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 starts inside the heart and courses on the surface to the left side of the heart. In some people, this vein is not available, too small or too tortuous. This difficulty may make implanting this lead impossible in about 5-10% of patients. 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 need to be changed every 5-7 years, which generally requires a small operation.