A pacemaker is a device that sends small electrical impulses to the heart muscle to make the heart muscle beat and prevent the heart rate from going too slow. A pacemaker has two parts — a generator and wires (leads, or electrodes) — and is placed in the chest under the skin. People may need a pacemaker for a variety of reasons — mostly due to one of a group of conditions called arrhythmias, in which the heart’s rhythm is abnormal. A pacemaker may also be used to treat fainting spells (syncope), congestive heart failure and hypertrophic cardiomyopathy.

The atria and ventricles work together, alternately contracting and relaxing to pump blood through the heart. The electrical system of the heart is the power source that makes this possible. Normally, the electrical impulse begins at the sinoatrial (SA) node, located in the right atrium. The electrical activity spreads through the walls of the atria, causing them to contract. The atria move the blood to fill the bottom chambers (the ventricles). Next, the electrical impulse travels through the AV node, located between the atria and ventricles. The AV node acts like a gate that slows the electrical signal before it enters the ventricles. This delay gives the atria time to contract while the ventricles are flaccid and relaxed. From the AV node, the electrical impulse travels through the His-Purkinje network, a pathway of specialized electricity-conducting fibers. Then the impulse travels into the muscular walls of the ventricles, causing them to contract. The ventricles are the actual pumps that move the blood through the circulation. The ventricles cannot beat by themselves and they have to receive the impulse from the top chambers (the atria). This sequence occurs with every heartbeat (usually 60-100 times per minute).

If the electrical pathway described above is interrupted for any reason, changes in the heart rate and rhythm occur that make a pacemaker necessary.

Normal aging of the heart may disrupt the heart rate, making it beating too slowly. Heart muscle damage resulting from a heart attack or valve surgery is another common cause of disruptions of your heartbeat. Some medications can affect the heart rate as well. For some, genetic conditions can cause an abnormal heart rate. Regardless of the underlying cause of an abnormal heart rate, a pacemaker can fix it. A pacemaker can often be implanted in your chest with a minor surgery. A pacemaker implant is generally a very safe procedure. However, as with any invasive procedure, there are risks. The risk of a complication at the time of a pacemaker implant procedure is low. But, over the long-term, about 1 in 10 patients do have some type of problem with their pacemaker pocket or leads.

CRT Pacemaker

Courtesy of St. Jude