CRT devices are often used to treat conditions where electrical signals do not flow through the heart normally. Bundle branch block is a condition where electrical signals travel too slowly through the bundle branches in the heart. This causes the ventricles to contract in a “dyssynchronous” or disorderly manner. This may lead to “congestive heart failure” or fluid build up in the lungs, as the heart muscle is weak and does not beat in an orderly fashion. Bundle branch block is common in patients with cardiomyopathy or heart muscle weakness related to coronary artery disease or other causes, leading to congestive heart failure.

The CRT device is implanted under your skin, beneath your collarbone and is connected to wires called leads which are inserted into the heart during surgery. A CRT device sends electrical signals to the heart or “paces” the heart to allow it to beat in a coordinated manner. This allows the ventricles (or “lower chambers”) of the heart to contract at the same time. This strengthens the heartbeat and increases the amount of blood pumped out of the heart.