PACEMAKERS

Introduction

Your heart is a muscular organ that pumps blood to all parts of your body to provide them with oxygen and nutrients. The normal heart is about the size of your clenched fist and sits directly underneath your breastbone. It pumps about 5 liters (approximately 5 quarts) of blood throughout the body each minute, which equals about 75 gallons or 285 liters of blood each day. This is accomplished by rhythmic relaxation and contraction of the heart. Each such cycle is called a "heart beat". Number of heart beats occurring per minute is called the "heart rate". An average person at rest has a heart rate of about 70 beats per minute.

The heart is divided up into four sections, called chambers. The two upper chambers are called the Atria, designated as left and right, and the two lower chambers are called the Ventricles, again designated as left and right. During a heart beat, the atria contract to squeeze blood into the ventricles below them, and then the ventricles pump that blood out into the body.

The contraction of the chambers of the heart is a muscular, energy requiring process. This energy is derived from the blood flow to the heart muscle which is carried by the coronary arteries. For each heart beat, the contraction of the heart muscle is initiated by electrical signals to the heart muscle. Every single heart beat requires an electrical impulse to initiate it. In absence of these electrical impulses or in case of the failure of their propagation to the various chambers of the heart, even perfectly healthy heart muscle will keep standing still, as if waiting for marching orders.

For the purpose of generating the above mentioned electrical impulses, every heart has what is called the "natural pacemaker", which produces the electrical signals that run through the heart to keep it beating. The "natural pacemaker" is a small mass of specialized cells named the Sinoatrial (SA) node, and is located in the top of the right atrium. Signals from this node travel through the atria and cause them to contract, sending their blood to the ventricles. The electrical signal itself then passes from the atria to the Atrioventricular (AV) node, so named because it sits in the center of the heart between the atria and the ventricles. This node is the sole electrical connection between the atria and the ventricles. It impedes the electrical signal for a fraction of a second in order to allow the blood to pass from the top chambers to the bottom, and then delivers it to the ventricles thorough nerve like fibers called Bundle Branches, in turn causing these chambers to contract and send blood out to the body.

What is a pacemaker?

A pacemaker is a small electrical device that runs on a battery and produces low voltage rhythmic electrical signals that keep the heart beating when the heart's own electrical signals are deficient. A pacemaker continuously "watches" the electrical system of your heart and provides the needed electrical signal if your heart does not do so. During periods when the heart produces its own electrical signal normally, the pacemaker does nothing except to continue to monitor.

A pacemaker system is made up of three parts:

1. The generator, a smooth, lightweight case containing a tiny computer and a battery which makes the electrical signals needed to pace the heart;
2. The connector or header, which is the part of the generator where the leads are attached; and
3. The leads, which are wires covered in soft, flexible plastic that are inserted into the heart to help the generator watch the heart and carry the generator’s signals to the heart.

A pacemaker may have one or two leads. A pacemaker with one lead is called a single-chamber pacemaker. Where this one lead sits depends on where the signal problem in your heart is. A pacemaker with two leads is called a dual-chamber pacemaker. One lead usually sits in your right atrium, and the other usually sits in your right ventricle. Which type of pacemaker you need depends upon the kind of rhythm disturbance you have and your overall heart function. Depending on your situation, your pacemaker will:

1. Supplement the function of your SA node, your natural pacemaker.
2. Ensure adequate electrical conduction from the upper chambers of the heart to the lower chambers.
3. Help your heart beat more efficiently by coordinating signals between the chambers.
4. Ensure that the heart beat at the required rate.
5. Some pacemakers are also "rate-adaptive", meaning that they can monitor your activity level change heart rate accordingly.

Why would I need a pacemaker?

Normally, the SA node automatically maintains a heart rate adequate for your body’s needs - for example, heart rate decreases during sleep and increases during exercise to match your body’s need for oxygen. Sometimes the signals coming from the SA node may be too slow (called sinus bradycardia), may alternate between being too fast and too slow (called sick sinus syndrome), or may occasionally stop (called sinus pause or sinus arrest). At other times the signals may form normally in the sinus node but fail to transmit from the upper to the lower chambers. This is called heart block. (The term heart block refers only a 'block' in he electrical system within the heart. It does not refer to blockages in the coronary arteries.) All the above conditions cause the heart to pump too slowly. This can cause symptoms such as dizziness or fainting. Pacemakers are usually recommended in these situations.

It must be noted, that pacemakers are used to treat slow heart beat. Pacemakers are only rarely useful in treating rapid heart beat.

Implanting the pacemaker

Pre-procedure

The implantation of a permanent pacemaker is a fairly simple surgical procedure that can be performed in the operating room or in the cardiac catheterization lab. When the decision to implant a pacemaker is made, you will receive pre-procedure instructions similar to the following:

1. Do not have anything to eat or drink for 6 hours before your procedure.
2. If you are a diabetic you may be instructed to reduce or not take your insulin or other diabetic medicine on the day of the procedure to avoid low blood sugar.
3. You may be asked stop taking aspirin or other blood thinners several days prior to the procedure to avoid unnecessary bleeding.
4. Blood tests may be required on the day of the procedure or before it.
5. Usually you will be asked to arrive in the hospital on the morning of the procedure several hours before the procedure so that you can be adequately prepared to undergo the surgery. After the procedure usual hospital stay is one day.

During the procedure

Immediately before your procedure, the skin area just beneath your shoulder and above the breast will be cleansed with special soap and may be shaved to remove excess hair. A mild sedative may be given to you to help you relax.

The procedure may take 1 to 2 hours to complete. It is usually done under local anesthesia, which means that the area where the pacemaker will be inserted will be numbed with an injection. You should not feel any pain during the procedure, and should inform the doctor or staff if you are having pain so that more medication may be given. The most common insertion method is called endocardial (inside the heart) implantation. An incision is made in the skin under the collarbone and a "pocket" is formed under the skin and in front of the muscle in the upper chest for the pacemaker generator to rest in. The lead or leads are then threaded through a major vein in your upper chest and into your heart with the help of x-ray monitors. Their position inside your heart is determined by electrical measurements. Once the leads are in place, they are hooked to the generator, which is then inserted into the pocket that has been made. The pacemakers settings are programmed, the incision is closed, and a sterile dressing is placed over the incision.

After the procedure

While in the hospital, your vital signs will be checked frequently, and your heart’s signal will be checked to make sure that the pacemaker is functioning correctly. Your incision will also be checked for bleeding or swelling. Pain medication will be available to make you more comfortable. It is important to tell the nurse if you feel any unusual symptoms such as hiccups that won’t go away, dizziness or chest pain. It’s normal to have some stiffness and pain to the area around the incision for about a week or so. In order to give the leads a chance to secure themselves in your vein and heart, do not lift the arm on the side the device was implanted above your shoulder.

• It will be a few days before you can go back to your daily activities, and you should take it easy with the arm on the side of implantation for several weeks. Your doctor will tell you when it is okay to go back to work.
• Do not lift your arm over your head for at least three weeks.
• Treat the insertion site with care. Avoid getting the incision site wet for about a week. This will help reduce the chances of infection.
• The bandage is usually taken off before you are discharged from the hospital. Small steri-strips (tapes) remain applied. These should be left in place until your doctor takes them off.
• Avoid vigorous exercise such as heavy lifting, running, or contact sports for six weeks.
• Monitor your temperature and insertion site, and notify your doctor if you develop a temperature or notice swelling, bleeding, redness, or drainage from your insertion site, or if you feel any of the symptoms you had before the pacemaker was implanted.

Risks of Pacemaker Implantation

Pacemaker implantation is a safe procedure. Procedural complications are rare, but do occur. These include but are not limited to:

• 5% chance of bleeding or severe bruising at the insertion site.
• 1% chance of puncture of lung puncture while obtaining access into the veins. The lung when punctured can deflate like a balloon. This usually requires insertion of a tube in the side of the chest to reinflate the lung. The lung then heals up in five to seven days.
• 1% chance of puncture of heart muscle. This may require specific treatment.
• 1% chance of infection.
• Other risks may apply, depending upon your general condition and other medical conditions that you might have.

Some discomfort is usual at the implant site, however this is usually easily controllable with simple pain killers.

Follow-up: Caring for your pacemaker

• You will have a follow up visit in the doctor’s office about one week after your procedure to check the insertion site and monitor for any problems.
• At about three months, you will have another doctor’s visit to check the pacemakers settings and readjust them to better help your heart and maximize pacemaker battery life.
• It is routine to check the pacemaker using transtelephonic monitoring equipment every one to two months to check the battery and to find any unexpected functional problems. Your doctor’s office will give you the necessary equipment free of charge to be used at home for this purpose.
• You may need to visit your doctor’s office for a detailed pacemaker check once a year.

Pacemaker batteries usually last for 5 to 10 years before they need to be replaced. Because the battery is sealed inside the pacemaker generator, replacing the battery requires that the entire generator be replaced. This procedure is simpler than the implantation procedure. The pocket where the generator sits is opened, the old generator is removed from the pocket and detached from the leads, the new generator is hooked to the leads and placed into the pocket, and the incision is closed. This is usually an outpatient procedure and does not require hospital admission. If the leads wear out and need to be replaced, a procedure similar to your original one will be needed. There is a small chance that the pacemaker can fail, but with the advances in pacemaker technology in recent years, the chance is remote. If your pacemaker were to fail, you would probably feel the same symptoms as you did before the pacemaker was inserted. Contact your doctor as soon as possible.

Your incision should heal completely in about two to three months. Continue to treat the insertion site with care. Don’t play with the pacemaker under your skin. You may feel some numbness or fullness in the area around the pacemaker for a few months that resolves as you become accustomed to the pacemaker.

Living with a pacemaker

1. Your pacemaker is registered with the manufacturer at the time of implant. You will be given an ID card which contains important information about your pacemaker before being discharged from the hospital. A printed card containing the same information will arrive in the mail in a few weeks. Keep this card in your wallet and show it to any doctor, dentist, or other medical professional you visit. You should carry it with you at all times to alert emergency personnel.
2. Your pacemaker is a metallic device and it may set off security devices such as those found in airports or libraries, and you may need to show your registration card to the security personnel.
3. Contact sports and other activities such as racquetball should be avoided due to the risk of bumping your pacemaker. However the pacemaker does not prevent you from exercising regularly. Your doctor can recommend an exercise program, if needed. Recommended activities are swimming, walking, bicycling, jogging, tennis, etc.
4. Most home appliances will not interfere with your pacemakers signal. These include electric drills, electric blankets, hair dryers, electric shavers, heating pads, metal detectors, microwave ovens, TV transmitters and remote control TV changers. Some of these devices have the potential to cause an occasional skipped beat, but most patients can use these devices without significant worry.
5. Avoid being close to very strong magnets, such as MRI equipment, heavy duty electrical equipment, radio-transmitting towers, ham radios, certain surgical instruments, and cellular phones.
6. Use of therapeutic magnets such as those for treating arthritis or muscle aches, etc. does not interfere with pacemaker function if the magnet stays at least six inches away from the device. Magnet mattress pads should not be used because these can modify the fucntion of your pacemaker.
7. Generally it is not possible to undergo an MRI test if you have an implanted pacemaker, because MRI uses a very strong magnetic field to obtain images. This magnetic field can dislodge your pacemaker.
8. Cellular phones, CB radios and ham radios can sometimes interfere with the function of some pacemakers. Cellular phone and CB radio antennas must remain at least six inches away from the pacemaker. Hence do not carry a cellular phone in your chest pocket, even when it is turned off. When using a cellular phone, hold it to the ear farthest from the pacemaker generator. Ham radio antenna should remain at least six feet away from the pacemaker.
9. Do not stand over the open hood of a running car as the engine generates a strong electrical field. It is okay to drive a car, however.

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© Tier Cardiology Group, PC.

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