What is a pacemaker insertion?

A pacemaker insertion is the implantation of a small electronic device that is usually placed in the chest (just below the collarbone) to help regulate slow electrical problems with the heart. A pacemaker may be recommended toensure that the heartbeat does not slow to a dangerously low rate.

The heart's electrical system

The heart is basically a pump made up of muscle tissue that is stimulated by electrical currents, which normally follow a specific circuit within the heart.

This normal electrical circuit begins in the sinus or sinoatrial (SA) node, which is a small mass of specialized tissue located in the right atrium(upper chamber) of the heart. The SA node generates an electrical stimulus at 60 to 100 times per minute (for adults) under normal conditions; this electrical impulse from the SA node starts the heartbeat.

The electrical impulse travels from the SA node via the atria to the atrioventricular (AV) node in the bottom of the right atrium. From there the impulse continues down an electrical conduction pathway called the Bundle of His and then on through the "His-Purkinje" system into the ventricles (lower chambers) of the heart. When the electrical stimulus occurs it causes the muscle to contract and pump blood to the rest of the body. This process of electrical stimulation followed by muscle contraction is what makes the heart beat.

A pacemaker may be needed when problems occur with the electrical conduction system of the heart. When the timing of the electrical stimulation of the heart to the heart muscle and the subsequent response of the heart's pumping chambers is altered, a pacemaker may help.

What is a pacemaker?

A pacemaker is composed of three parts: a pulse generator, one or more leads, and an electrode on each lead. A pacemaker signals the heart to beat when the heartbeat is too slow or irregular.

A pulse generator is a small metal case that contains electronic circuitry with a small computer and a battery that regulate the impulses sent to the heart.

The lead (or leads) is an insulated wire that is connected to the pulse generator on one end, with the other end placed inside one of the heart's chambers. The lead is almost always placed so that it runs through a large vein in the chest leading directly to the heart. The electrode on the end of a lead touches the heart wall. The lead delivers the electrical impulses to the heart. It also senses the heart's electrical activity and relays this information back to the pulse generator. Pacemaker leads may be positioned in the atrium (upper chamber) or ventricle (lower chamber) or both, depending on the medical condition.

If the heart's rate is slower than the programmed limit, an electrical impulse is sent through the lead to the electrode and causes the heart to beat at a faster rate.

When the heart beats at a rate faster than the programmed limit, the pacemaker generally monitors the heart rate and will not pace. Modern pacemakers are programmed to work on demand only, so they do not compete with natural heartbeats. Generally, no electrical impulses will be sent to the heart unless the heart's natural rate falls below the pacemaker's lower limit.

A newer type of pacemaker, called a biventricular pacemaker, is currently used in the treatment of specific types of heart failure. Sometimes in heart failure, the two ventricles do not pump in a normal manner. Ventricular dyssynchrony is a common term used to describe this abnormal pumping pattern. When this happens, less blood is pumped by the heart. A biventricular pacemaker paces both ventricles at the same time, increasing the amount of blood pumped by the heart. This type of treatment is called cardiac resynchronization therapy or CRT.

After a pacemaker insertion, regularly scheduled appointments will be made to ensure the pacemaker is functioning properly. The doctor uses a special computer, called a programmer, to review the pacemaker's activity and adjust the settings when needed.

Other related procedures that may be used to assess the heart include resting and exercise electrocardiogram (ECG) , Holter monitor, signal-averaged ECG, cardiac catheterization , chest X-ray , computed tomography (CT scan) of the chest , echocardiography , electrophysiology studies , magnetic resonance imaging (MRI) of the heart , myocardial perfusion scan (stress) , myocardial perfusion scan (resting) , radionuclide angiography , and cardiac CT scan . Please see these procedures for additional information. Note that although an MRI is a very safe procedure, the magnetic fields used by the MRI scanner may interfere with the pacemaker's function. Any patient with a pacemaker should always speak with his or her cardiologist before undergoing an MRI.

Reasons for the procedure

A pacemaker may be inserted in order to stimulate a faster heart rate when the heart is beating too slowly, and causing problems that cannot otherwise be corrected.

Problems with the heart rhythm may cause difficulties because the heart is unable to pump an adequate amount of blood to the body. If the heart rate is too slow, the blood is pumped too slowly. If the heart rate is too fast or too irregular, the heart chambers are unable to fill up with enough blood to pump out with each beat. When the body does not receive enough blood, symptoms such as fatigue, dizziness, fainting, and/or chest pain may occur.

Some examples of heart rate and rhythm problems for which a pacemaker might be inserted include:

• Bradycardia. This occurs when the sinus node causes the heart to beat too slowly.
• Tachy-brady syndrome. This is characterized by alternating fast and slow heartbeats.
• Heart block. This occurs when the electrical signal is delayed or blocked after leaving the SA node; there are several types of heart blocks.

There may be other reasons for your doctor to recommend a pacemaker insertion.

Risks of the procedure

Possible risks of pacemaker include, but are not limited to, the following:

• Bleeding from the incision or catheter insertion site
• Damage to the vessel at the catheter insertion site
• Infection of the incision or catheter site
• Pneumothorax. If the nearby lung is inadvertently punctured during the procedure, leaking air becomes trapped in the pleural space (outside the lung but within the chest wall); this can cause breathing difficulties and in extreme cases may cause the lung to collapse.

If you are pregnant or suspect that you may be pregnant, you should notify your health care provider. If you are breastfeeding, you should notify your health care provider.

Patients who are allergic to or sensitive to medications or latex should notify their doctor. For some patients, having to lie still on the procedure table for the length of the procedure may cause some discomfort or pain. There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.

Before the procedure

Your doctor will explain the procedure to you and offer you the opportunity to ask any questions that you might have about the procedure:

• You will be asked to sign a consent form that gives your permission to do the test. Read the form carefully and ask questions if something is not clear.
• Notify your doctor if you are sensitive to or are allergic to any medications, iodine, latex, tape, or anesthetic agents (local and general).
• You will need to fast for a certain period of time prior to the procedure. Your doctor will notify you how long to fast, usually overnight.
• If you are pregnant or suspect that you are pregnant, you should notify your doctor.
• Notify your doctor of all medications (prescription and over-the-counter) and herbal or other supplements that you are taking.
• Notify your doctor if you have heart valve disease, as you may need to receive an antibiotic prior to the procedure.
• Notify your doctor if you have a history of bleeding disorders or if you are taking any anticoagulant (blood-thinning) medications, aspirin, or other medications that affect blood clotting. It may be necessary for you to stop some of these medications prior to the procedure.
• Your doctor may request a blood test prior to the procedure to determine how long it takes your blood to clot. Other blood tests may be done as well.
• You may receive a sedative prior to the procedure to help you relax. If a sedative is given and there is a possibility that you may be discharged, you will need someone to drive you home. You will likely spend at least one night in the hospital after the procedure for observation and to ensure the pacemaker functions properly.
• Based on your medical condition, your doctor may request other specific preparation.