Pacemaker

What Is a Pacemaker

A pacemaker is a small device that's placed in the chest to help control abnormal heart rhythms. This device uses electrical pulses to prompt the heart to beat at a normal rate.
Pacemakers are used to treat Arrhythmias are problems with the rate or rhythm of the heartbeat. During an arrhythmia, the heart can beat too fast, too slow, or with an irregular rhythm.

A heartbeat that's too fast is called tachycardia .A heartbeat that's too slow is called bradycardia. During an arrhythmia, the heart may not be able to pump enough blood to the body. This can cause symptoms such as fatigue (tiredness), shortness of breath, or fainting. Severe arrhythmias can damage the body's vital organs and may even cause loss of consciousness or death. A pacemaker can relieve some arrhythmia symptoms, such as fatigue and fainting. A pacemaker also can help a person who has abnormal heart rhythms resume a more active lifestyle.

Understanding the Heart's Electrical System

Your heart has its own internal electrical system that controls the rate and rhythm of your heartbeat. With each heartbeat, an electrical signal spreads from the top of your heart to the bottom. As the signal travels, it causes the heart to contract and pump blood.
Each electrical signal normally begins in a group of cells called the sinus node or sinoatrial (SA) node. As the signal spreads from the top of the heart to the bottom, it coordinates the timing of heart cell activity.
First, the heart's two upper chambers, the atria, contract. This contraction pumps blood into the heart's two lower chambers, the ventricles. The ventricles then contract and pump blood to the rest of the body. The combined contraction of the atria and ventricles is a heartbeat.



Faulty electrical signalling in the heart causes arrhythmias. Pacemakers use low-energy electrical pulses to overcome this faulty electrical signalling. Pacemakers can:

• • Speed up a slow heart rhythm.
• • Help control an abnormal or fast heart rhythm.
• • Make sure the ventricles contract normally if the atria are quivering instead of beating with a normal rhythm (a condition called atrial fibrillation).
• • Coordinate electrical signalling between the upper and lower chambers of the heart.
• • Coordinate electrical signalling between the ventricles. Pacemakers that do this are called cardiac resynchronization therapy (CRT) devices. CRT devices are used to treat heart failure
• • Prevent dangerous arrhythmias caused by a disorder called long QT syndrome.

Pacemakers also can monitor and record your heart's electrical activity and heart rhythm. Newer pacemakers can monitor your blood temperature, breathing rate, and other factors. They also can adjust your heart rate to changes in your activity.
Pacemakers can be temporary or permanent. Temporary pacemakers are used to treat short-term heart problems, such as a slow heartbeat that's caused by a heart attack, heart surgery, or an overdose of medicine.
Temporary pacemakers also are used during emergencies. They might be used until your doctor can implant a permanent pacemaker or until a temporary condition goes away. If you have a temporary pacemaker, you'll stay in a hospital as long as the device is in place. Permanent pacemakers are used to control long-term heart rhythm problems. This article mainly discusses permanent pacemakers, unless stated otherwise. Doctors also treat arrhythmias with another device called an implantable Cardioverter defibrillator (ICD). An ICD is similar to a pacemaker. However, besides using low-energy electrical pulses, an ICD also can use high-energy pulses to treat life-threatening arrhythmias. 

Who Needs a Pacemaker

Doctors recommend pacemakers for many reasons. The most common reasons are bradycardia and heart block.
Bradycardia is a heartbeat that is slower than normal. Heart block is a disorder that occurs if an electrical signal is slowed or disrupted as it moves through the heart.
Heart block can happen as a result of aging, damage to the heart from a heart attack, or other conditions that disrupt the heart's electrical activity. Some nerve and muscle disorders also can cause heart block, including muscular dystrophy.

Your doctor also may recommend a pacemaker if:

• • Aging or heart disease damages your sinus node's ability to set the correct pace for your heartbeat. Such damage can cause slower than normal heartbeats or long pauses between heartbeats. The damage also can cause your heart to switch between slow and fast rhythms. This condition is called sick sinus syndrome.
• • You've had a medical procedure to treat an arrhythmia called atrial fibrillation. A pacemaker can help regulate your heartbeat after the procedure.
• • You need to take certain heart medicines, such as beta blockers. These medicines can slow your heartbeat too much.
• • You faint or have other symptoms of a slow heartbeat. For example, this may happen if the main artery in your neck that supplies your brain with blood is sensitive to pressure. Just quickly turning your neck can cause your heart to beat slower than normal. As a result, your brain might not get enough blood flow, causing you to feel faint or collapse.
• • You have heart muscle problems that cause electrical signals to travel too slowly through your heart muscle. Your pacemaker may provide cardiac resynchronization therapy (CRT) for this problem. CRT devices coordinate electrical signalling between the heart's lower chambers.
• • You have long QT syndrome, which puts you at risk for dangerous arrhythmias.

Doctors also may recommend pacemakers for people who have certain types of congenital heart disease or for people who have had heart transplants. Children, teens, and adults can use pacemakers.
Before recommending a pacemaker, your doctor will consider any arrhythmia symptoms you have, such as dizziness, unexplained fainting, or shortness of breath. He or she also will consider whether you have a history of heart disease, what medicines you're currently taking, and the results of heart tests.

How Does a Pacemaker Work.

A pacemaker consists of a battery, a computerized generator, and wires with sensors at their tips. (The sensors are called electrodes.) The battery powers the generator, and both are surrounded by a thin metal box. The wires connect the generator to the heart.
A pacemaker helps monitor and control your heartbeat. The electrodes detect your heart's electrical activity and send data through the wires to the computer in the generator.
If your heart rhythm is abnormal, the computer will direct the generator to send electrical pulses to your heart. The pulses travel through the wires to reach your heart.
Newer pacemakers can monitor your blood temperature, breathing, and other factors. They also can adjust your heart rate to changes in your activity.
The pacemaker's computer also records your heart's electrical activity and heart rhythm. Your doctor will use these recordings to adjust your pacemaker so it works better for you.
Your doctor can program the pacemaker's computer with an external device. He or she doesn't have to use needles or have direct contact with the pacemaker.
Pacemakers have one to three wires that are each placed in different chambers of the heart.

• • The wires in a single-chamber pacemaker usually carry pulses from the generator to the right ventricle (the lower right chamber of your heart).
• • The wires in a dual-chamber pacemaker carry pulses from the generator to the right atrium (the upper right chamber of your heart) and the right ventricle. The pulses help coordinate the timing of these two chambers' contractions.
• • The wires in a biventricular pacemaker carry pulses from the generator to an atrium and both ventricles. The pulses help coordinate electrical signalling between the two ventricles. This type of pacemaker also is called a cardiac resynchronization therapy (CRT) device.

Types of Pacemaker Programming

The two main types of programming for pacemakers are demand pacing and rate-responsive pacing.
A demand pacemaker monitors your heart rhythm. It only sends electrical pulses to your heart if your heart is beating too slowly or if it misses a beat.
A rate-responsive pacemaker will speed up or slow down your heart rate depending on how active you are. To do this, the device monitors your sinus node rate, breathing, blood temperature, and other factors to determine your activity level.
Your doctor will work with you to decide which type of pacemaker is best for you.

How Will a Pacemaker Affect My Lifestyle.

Once you have a pacemaker, you have to avoid close or prolonged contact with electrical devices or devices that have strong magnetic fields. 
Devices that can interfere with a pacemaker include:

• • Cell phones and MP3 players (for example, iPods)
• • Household appliances, such as microwave ovens
• •High-tension wires
• •Metal detectors
• • Industrial welders
• • Electrical generators

These devices can disrupt the electrical signalling of your pacemaker and stop it from working properly. You may not be able to tell whether your pacemaker has been affected.
How likely a device is to disrupt your pacemaker depends on how long you're exposed to it and how close it is to your Pacemaker. To be safe, some experts recommend not putting your cell phone or MP3 player in a shirt pocket over your pacemaker (if the devices are turned on).

You may want to hold your cell phone up to the ear that's opposite the site where your pacemaker is implanted. If you strap your MP3 player to your arm while listening to it, put it on the arm that's farther from your pacemaker.
You can still use household appliances, but avoid close and prolonged exposure, as it may interfere with your pacemaker.
You can walk through security system metal detectors at your normal pace. Security staff can check you with a metal detector wand as long as it isn't held for too long over your pacemaker site. You should avoid sitting or standing close to a security system metal detector. Notify security staff if you have a pacemaker.
Also, stay at least 2 feet away from industrial welders and electrical generators.
Some medical procedures can disrupt your pacemaker. These procedures include:

• Magnetic resonance imaging, or MRI
• Shock-wave lithotripsy to get rid of kidney stones
• Electro cauterization to stop bleeding during surgery

Let all of your doctors, dentists, and medical technicians know that you have a pacemaker. Your doctor can give you a card that states what kind of pacemaker you have. Carry this card in your wallet. You may want to wear a medical ID bracelet or necklace that states that you have a pacemaker.

Physical Activity.

In most cases, having a pacemaker won't limit you from doing sports and exercise, including strenuous activities. You may need to avoid full-contact sports, such as football. Such contact could damage your pacemaker or shake loose the wires in your heart. Ask your doctor how much and what kinds of physical activity are safe for you.

Ongoing Care.

Your doctor will want to check your pacemaker regularly (about every 3 months). Over time, a pacemaker can stop working properly because:

• • Its wires get dislodged or broken
• • Its battery gets weak or fails
• • Your heart disease progresses
• • Other devices have disrupted its electrical signalling

To check your pacemaker, your doctor may ask you to come in for an office visit several times a year. Some pacemaker functions can be checked remotely using a phone or the Internet.
Your doctor also may ask you to have an EKG (electrocardiogram) to check for changes in your heart's electrical activity.

Battery Replacement.

Pacemaker batteries last between 10 to 15 years, depending on how active the pacemaker is. Your doctor will replace the generator along with the battery before the battery starts to run down.
Replacing the generator and battery is less-involved surgery than the original surgery to implant the pacemaker. Your pacemaker wires also may need to be replaced eventually.
Your doctor can tell you whether your pacemaker or its wires need to be replaced when you see him or her for follow-up visits.