Pacemakers and implantable cardiac defibrillators

Description
A cardiac pacemaker is an electrical device that senses your heart rate and stimulates your heart to beat when it beats too slowly or not at all. A pacemaker has two parts, the lead wire and the pulse generator. The lead wire conducts electrical impulses from the pacemaker's pulse generator to your heart muscle. The pulse generator is small and thin, weighing about 2 to 4 ounces. It's powered by a lithium battery that can last from five to 10 years, depending on the usage and features of the pacemaker.
An implantable cardiac defibrillator (ICD) is a device that detects life-threatening arrhythmias and delivers an electrical shock to the heart to convert the rhythm back to normal. It also consists of a generator and leads.

The type of pacemaker you're given will depend on your general health, medical history and current diagnosis, as well as your doctor's preferences. A combination of pacemaker and ICD is also available. Permanent pacemakers and ICDs are inserted inside the chest and can be programmed electronically, even after they've been implanted.


Purpose
The heart has its own natural pacemaker called the sinus node. When the electrical system of the heart works as it should, electrical impulses travel across the heart from the sinus node to stimulate the heart to beat regularly. If the heart's electrical system is damaged or becomes dysfunctional, an artificial pacemaker may be needed to do the job instead. The artificial pacemaker helps your heart pump blood at a normal rate and rhythm when your body's natural pacemaker isn't working. In turn, this will prevent the symptoms that can be caused by a heartbeat that's too slow or ineffective, such as dizziness or lightheadedness, fainting, intolerance to exercise or signs of heart failure.
People who have certain dangerous, sustained heart rhythms may be candidates for ICDs.


Indications
Pacemakers are most often used when the heart rhythm is too slow or uneven. Heart rhythm problems are usually caused by problems with the sinus node or the electrical pathways to the rest of the heart. Diagnosis is made from an electrocardiogram (a recording of the electrical activity of the heart), a prolonged recording of your heart electrical activity (through a Holter monitor or continuous loop recorder), or sometimes a special test in a cardiac catheterization lab.
Your doctor will want to ensure that medications are not causing your rhythm problem, although sometimes a pacemaker will be inserted if you must take medicine that causes a slow heartbeat. Most pacemakers used today can adjust your heart rate to your needs, such as when you increase your activity level.

ICDs are indicated if you have survived life-threatening arrhythmias, such as sustained ventricular tachycardia and ventricular fibrillation, that are not associated with a heart attack. If you're considered at high risk for cardiac arrest, you may also receive an ICD.

Researchers are currently studying the use of pacemakers and ICDs in the treatment of other heart conditions, such as atrial fibrillation (rapid, irregular heart rhythm of the upper chamber of the heart) and congestive heart failure (a condition in which the heart doesn't pump effectively). Sometimes, pacemakers are used to treat fainting spells that result from heart rhythms that are too slow.


Patient preparation
You will probably be told not to eat or drink anything after midnight on the day before the surgery. Your doctor will order routine blood and urine tests, as well as a chest X-ray and an electrocardiogram. Follow any specific instructions given by your doctor. Ask your doctor what to expect during recovery and when you can resume normal activity. Also, make sure someone is available to drive you home after you're discharged from the hospital.

Procedure
The procedure for placing a pacemaker and ICD are very similar. The pacemaker or ICD will be implanted near the left or right shoulder -- tell your doctor if you have a preference. In the hospital, you'll probably be given medication through an IV in your arm to help you relax, but you will typically remain awake through the procedure. (If you're getting an ICD, you may receive general anesthesia.) Then, your chest will be washed, shaved and numbed with anesthetic. To create a small "pocket," the doctor will make a small incision in the skin under the collarbone. The lead wire or wires will be threaded through the incision into a vein in your chest and guided into the heart. The doctor will do this with the help of fluoroscopy, a special type of X-ray. Then, the pulse generator will be attached to the leads and placed in the pocket.
After testing to ensure the pacemaker or ICD is working properly, the incision will be stitched and covered with a bandage. A chest X-ray will confirm proper positioning of the leads, as well as help the doctor check for any possible problems. The procedure takes about one to three hours.


Postprocedure care
You may need to spend up to two days in the hospital. A second electrocardiogram will be done before you're discharged. For the first week, don't lift your arm above your shoulder on the side of the pacemaker or ICD. This will give the leads a chance to firmly attach inside your heart. Also avoid driving for about one week and strenuous activities for at least two weeks. You may be able to resume other normal activities right away. Your doctor will give you specific instructions. You'll probably need to return for a follow-up visit about a week after the procedure to have your stitches removed.
You may learn how to transmit data from the pacemaker or ICD to your doctor through a special phone link in your home. Transmitting the data, usually every two to three months, helps ensure the device is working properly. A new pacemaker and ICD are now available that send data to the doctor at any time through a device similar to a cell phone.

Replacing the battery requires a second surgical procedure. This procedure is usually shorter and simpler than the original operation, and is often done as an outpatient procedure. Sometimes the leads must also be replaced. This procedure is also similar to the original implantation. How often the batteries need to be replaced depends on how often the pacemaker or ICD is required to stimulate or shock your heart.


Benefits
A pacemaker can relieve symptoms of dizziness, fainting, exercise intolerance and symptoms of heart failure such as shortness of breath. It can allow you to enjoy an improved or even normal activity level. An ICD can reduce your risk of dying from cardiac arrest (a condition in which your heart stops beating) or a dangerous arrhythmia.

Risks
Problems with pacemakers and ICDs are uncommon, but may include:
reaction to the anesthesia used during surgery
puncture of the lung, vein, or heart by a needle or the lead wires
infection or bleeding of the pacemaker pocket
mechanical or electrical failure of the leads or pacemaker
displacement or breakage of the leads or device

Considerations
Contact your doctor immediately if your original symptoms return, you develop prolonged hiccups or twitching of your arm or chest muscles, or your pulse becomes abnormally slow, fast or irregular. You'll be given a pacemaker or ICD ID card that you should carry with you at all times. It lists the type of device you have and the manufacturer, as well as other important information in case you need emergency care. Also, avoid hard physical contact to the device, such as the shoulder impact that occurs when firing a rifle or possibly through contact sports such as football. Before any medical or dental procedures, let the practitioner know about your pacemaker or ICD.
Due to the device's electrical nature, also keep the following points in mind.

Ask your doctor about the need to avoid powerful electromagnetic fields. This may include magnetic resonance imaging (MRI) devices, power plants, junkyards with large magnets and amusement park rides. You may also need to avoid working on running car engines or using arc welding equipment.

Your pacemaker or ICD may set off metal detectors used at airports or other facilities, but the detectors aren't likely to affect the device itself. Request airport security to use hand searching rather than a handheld metal detector.

A cell phone may interfere with your pacemaker or ICD. It's safe to use a cell phone next to your ear, but keep a distance of 6 inches between the phone and the pacemaker. Don't carry a cell phone that's turned on in your breast pocket over the pacemaker. Cordless phones intended for home use do not pose a problem.

Do not linger in store entrances or exits. The antitheft devices may affect your pacemaker or ICD if exposure is lengthy. (This is a greater concern for people who have ICDs.)

Although you may occasionally see warnings in eating areas, modern pacemakers and ICDs are not affected by microwave ovens.

Pregnancy-specific information
Some women may develop irregular heart rhythm patterns during pregnancy. Unless you have an underlying heart disease or the symptoms evolve, treatment may not be necessary. If you have a diagnosed heart condition before you get pregnant, consult a cardiologist (a doctor who specializes in heart conditions) to discuss potential risk factors during pregnancy. During pregnancy, pacemakers are usually tolerated well when used to treat heart block (when the electrical impulses that control heart rate travel slowly, intermittently or not at all).

Senior-specific information
Elderly adults and people who have heart disease have a higher rate of problems with the sinus node, the heart's natural pacemaker. (When the electrical system of the heart works as it should, electrical impulses travel across the heart from the sinus node to stimulate the heart to beat regularly.) Sick sinus syndrome, an inability of the sinus node to generate or transmit electrical impulses, often results in the need for a pacemaker. More than 70 percent of permanent pacemakers are implanted in people who are older than age 70.