With heart failure, the heart becomes enlarged and its electrical systems become stretched. This interferes with how the parts of the heart coordinate to contract and pump blood, making it inefficient.

Cardiac Resynchronization Therapy (CRT), or biventricular pacing, involves using a pacemaker, a small, implanted device, to coordinate the heart’s beating, helping its chambers pump together more efficiently.

Pacemakers send low-energy electrical impulses to the heart to help control the rhythm and rate of the heartbeat. There are several types:

  • Transvenous pacemakers: The most common type of CRT pacemaker is a traditional transvenous pacemaker, which sends electrical impulses via wires implanted in the veins.
  • Wireless pacemakers: A wireless pacemaker uses ultrasound energy to deliver pacing signals to the left ventricle. The ventricles are the two lower chambers of the heart.
  • Epicardial pacemakers: A surgeon places electrodes on the surface of the heart. Doctors may use this type when the structure of the heart or veins makes using another type difficult.

Doctors may recommend a CRT pacemaker with an integrated defibrillator, called a CRT-D device, for people at higher risk of dangerous heart rhythms or arrhythmias. A CRT-D device can track a person’s heart rate and deliver an electric shock if it detects an irregular or very fast rhythm. This can help prevent sudden cardiac arrest, which is when the heart stops beating suddenly.

CRT is not suitable for everyone with heart failure. Medication is a first-line treatment for those with mild to moderate symptoms. Ideal candidates for CRT may fit the following criteria:

  • moderate to severe symptoms
  • symptoms not improving with medication
  • reduced ejection fraction, a measure of how much blood the left ventricle pumps out with each contraction
  • wide QRS complex, which is visible on an electrocardiogram (ECG)
  • left bundle branch block, which affects the conduction of electrical impulses

People who do not fit this criteria may also benefit, but doctors are less certain about the benefits. Doctors may not recommend CRT to people who fit the criteria but have other health conditions, such as dementia or advanced cancer.

CRT has many benefits for a person’s health and quality of life, including:

  • more energy
  • better ability to exercise
  • less shortness of breath
  • better mood and emotional health
  • less likelihood of hospitalization
  • lower risk of death

The procedure to implant a transvenous CRT pacemaker typically requires local anesthesia given via an injection. A person is awake during the procedure and may feel a pulling sensation. The procedure lasts around 2 hours.

A cardiologist will make a 2-inch cut just below the collarbone, usually on the left side of the chest. Using X-rays to guide them, they will insert the pacemaker’s wires into a vein and into the correct chamber of the heart. They will then connect the other ends of the leads to a pacemaker, which the cardiologist will fit into a small pocket between the skin and chest muscle.

A person typically stays overnight in the hospital and will need to avoid vigorous activity for a few weeks. They may feel an improvement in days, but it could take several months.