A pacemaker is a small, battery-operated device that senses when your heart is beating irregularly or too slowly. It sends a signal to your heart that makes your heart beat at the correct pace.

Newer pacemakers weigh as little as 1 ounce. A pacemaker usually has 2 parts:

• The generator contains the battery and the information to control the heartbeat.
• The leads are wires that connect the heart to the generator and carry the electrical messages to the heart.

A pacemaker must be implanted under the skin. This procedure usually takes about 1 hour. You will be given a sedative to help you relax. You will be awake during the procedure.

A small incision (cut) is made, usually on the left side of the chest below your collarbone. The pacemaker generator is then placed under the skin at this location.

Using live x-rays to see the area, the doctor puts the leads through the incision, into a vein, and then into the heart. The leads are connected to the generator. The skin is closed with stitches. Most patients go home within 1 day of the procedure.

Two kinds of pacemakers -- transcutaneous and transvenous pacemakers -- are used only in medical emergencies. They are not permanent pacemakers.

Pacemakers may be used for people who have heart problems that cause their heart to beat too slowly. A slow heartbeat is called bradycardia. Two common problems that cause a slow heartbeat are sinus node disease and heart block.

When your heart beats too slowly, your body and brain may not get enough oxygen. Symptoms may be lightheadedness, tiredness, fainting spells, and shortness of breath.

Some, pacemakers can be used to stop a heart rate that is too fast (tachycardia) or that is irregular.

Other types of pacemakers can be used in severe heart failure. These are called biventricular pacemakers. They match up the beating of both sides of the heart.

All of today's biventricular pacemakers can also work as implantable cardio-defibrillators (ICD), which restore a normal heartbeat.

Possible complications of pacemaker surgery are:

• Abnormal heart rhythms
• Bleeding
• Punctured lung. This is rare.
• Infection
• Puncture of the heart, which can lead to bleeding around the heart. This is rare.

A pacemaker can usually sense if the heartbeat is above a certain rate. When it is above that rate, the pacemaker will stop sending signals to the heart. The pacemaker can also sense when the heartbeat slows down too much. It will automatically turn back on and start pacing the heartbeat again.

Always tell your doctor or nurse what drugs you are taking, even drugs or herbs you bought without a prescription.

The day before your surgery:

• Shower and shampoo well.
• You may be asked to wash your whole body below your neck with a special soap.

On the day of the surgery:

• You may be asked not to drink or eat anything after midnight the night before your procedure. This includes chewing gum and breath mints. Rinse your mouth with water if it feels dry, but be careful not to swallow.
• Take your drugs your doctor told you to take with a small sip of water.

Your doctor or nurse will tell you when to arrive at the hospital.

You will probably be able to go home after 1 day. You should be able to return to your normal activity level quickly.

Talk with your doctor about how much you can use the arm on the side of your body where the pacemaker was placed. You may be advised not to lift anything heavier than 10 to 15 pounds and to avoid a lot of pushing, pulling, or twisting your arm for 2 to 3 weeks. You may also be told not to raise your arm above your shoulder for 6 weeks

When you leave the hospital, you will be given a card to keep in your wallet. This card lists the details of your pacemaker and has contact information for emergencies. You should always carry this wallet card with you.

Pacemakers are often able to help keep your heart rhythm and heart rate at a level that is safe for you. The pacemaker battery lasts about 6 to 15 years. Your doctor will check the batter regularly and replace it when necessary.

Epstein AE, DiMarco JP, Ellenbogen KA, Estes NA 3rd, Freedman RA, Gettes LS, et al. ACC/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the ACC/AHA/NASPE 2002 guideline update for implantation of cardiac pacemakers and antiarrhythmia devices): developed in collaboration with the American Association for Thoracic Surgery and Society of Thoracic Surgeons. Circulation. 2008;117(21): e350-408.

Hayes DL, Zipes DP. Cardiac Pacemakers and Cardioverter-Defibrillators. In: Libby P, Bonow RO, Mann DL, Zipes DP. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 34.