A permanent pacemaker is a small device that is implanted under the skin and sends electrical signals to start or regulate a slow heartbeat. A permanent pacemaker may be used to stimulate the heartbeat if the heart's natural pacemaker (the sinoatrial, or SA, node) is not functioning properly, has developed an abnormal heart rate or rhythm, or if the electrical pathways are blocked.
Children's pacemakers may be placed under the skin in one of several locations. Young children (infants, toddler, preschool, and young school-aged children) often have the pacemaker generator placed in the abdomen, since the fatty tissue found there can help protect the generator from normal everyday childhood activities such as playing. As a child gets older (nearing adolescence), the generator is often placed in the shoulder area, just under the collarbone.
An implantable cardioverter defibrillator (ICD) is a small device, similar to a pacemaker, that is implanted under the skin, often in the shoulder area, just under the collarbone. An ICD senses the rate of the heartbeat. When the heart rate exceeds a rate programmed into the device, the ICD delivers a small, electrical shock to the heart to slow the heart rate. Many newer ICDs can also function as a pacemaker by delivering an electrical signal to regulate a heart rate that is too slow.
When the heart's natural pacemaker has a dysfunction, the signals it sends out may become erratic: either too slow, too fast, or too irregular to stimulate adequate contractions of the heart chambers. When the heartbeat becomes erratic, it is referred to as an arrhythmia (an abnormal rhythm of the heart, which can cause the heart to pump less effectively).
Arrhythmias can cause problems with contractions of the heart chambers by:
- Not allowing the chambers to fill with an adequate amount of blood because the electrical signal is causing the heart to pump too fast.
- Not allowing a sufficient amount of blood to be pumped out to the body because the electrical signal is causing the heart to pump too slow or too irregularly.
The heart is, in the simplest terms, a pump made up of muscle tissue. Like all pumps, the heart requires a source of energy in order to function. The heart's pumping energy comes from a built-in, electrical, conduction system.
The pulse rate is a measurement of the heart rate, or the number of times the heart beats per minute. As the heart pushes blood through the arteries, the arteries expand and contract with the flow of the blood, and this can be felt in various points in the body as a pulse. Taking a pulse not only measures the heart rate, but also can indicate the following:
- Heart rhythm (abnormal rhythm may indicate a heart disorder).
- Strength of the pulse (a weak pulse may indicate a fast heartbeat in which some beats are too weak to feel, heart failure, or a low volume of blood in the circulatory system).
Many pacemakers provide varying rates, depending on your child's activity level and other factors. The pulse rate may fluctuate and increase with exercise, illness, injury, and emotions. Girls ages 12 and older and women, in general, tend to have faster heart rates than do boys and men. Athletes, such as runners, who do a lot of cardiovascular conditioning may have slow heart rates and experience no problems.
How to check your child's pulse
As the heart forces blood through the arteries, feel the beats by firmly pressing on the arteries, which are located close to the surface of the skin at certain points of the body. The pulse can be found on the side of the lower neck, on the inside of the elbow, or at the wrist. When taking a pulse:
- Using the first and second fingertips, press firmly but gently on the arteries until you feel a pulse.
- Begin counting the pulse when the clock's second hand is on the 12.
- Count the pulse for 60 seconds (or for 15 seconds and then multiply by four to calculate beats per minute).
- When counting, do not watch the clock continuously, but concentrate on the beats of the pulse. If you have trouble with this method, try a digital kitchen timer and set it for one minute. Stop counting when the timer alarms.
If unsure about your results, ask another person to count for you.
If you are having difficulty in finding your child's pulse, consult your child's physician for additional instruction.
An electrical stimulus is generated by the sinus node (also called the sinoatrial node, or SA node), which is a small area of specialized tissue located in the right atrium (right upper chamber) of the heart. Under normal conditions, the sinus node generates an electrical stimulus every time the heart beats (60 to 190 times per minute, depending on the age of the child and his/her activity level). This electrical stimulus travels down through the conduction pathways (similar to the way electricity flows through power lines from the power plant to your house) and causes the heart's chambers to contract and pump out blood. The right and left atria (the two upper chambers of the heart) are stimulated first and contract a short period of time before the right and left ventricles (the two lower chambers of the heart).
The electrical impulse then travels from the sinus node to the atrioventricular (AV) node, where it stops for a very short period, and continues down the conduction pathways via the bundle of His into the ventricles. The bundle of His divides into right and left pathways to provide electrical stimulation to both ventricles.
Normally, the electrical impulse moves through the heart's conduction system, and the heart contracts. Each contraction represents one heartbeat. The atria contract a fraction of a second before the ventricles so the blood empties into the ventricles before the ventricles contract.
Under some conditions, almost all heart tissue is capable of starting a heartbeat, or becoming the "pacemaker," just like the sinus node. An arrhythmia may occur when:
- The heart's natural pacemaker (the sinus node) develops an abnormal rate or rhythm.
- The normal conduction pathway is interrupted.
- Another part of the heart takes over as pacemaker.
In any of these situations, the body may not receive enough blood because the heart cannot pump out an adequate amount with each beat as a result of the arrhythmia's effects on the heart rate. The effects on the body are often the same, however, whether the heartbeat is too fast, too slow, or too irregular.
A permanent pacemaker has two components, including the following:
- A pulse generator which has a sealed lithium battery and an electronic circuitry package. The pulse generator produces the electrical signals that make the heart beat. Many pulse generators also have the capability to receive and respond to signals that are sent by the heart itself.
- One or two wires (also called leads). Leads are insulated, flexible wires that conduct electrical signals to the heart from the pulse generator. The leads may also relay signals from the heart to the pulse generator. One end of the lead is attached to the pulse generator and the electrode end of the lead is positioned in the atrium (the upper chamber of the heart) or in the ventricle (the lower chamber of the heart).
Older pacemakers sent out electrical signals at a constant rate, regardless of the heart's own rate. Pacemaker technology is now much more advanced. Today, pacemakers can "sense" when the heart's natural rate falls below the rate that has been programmed into the pacemaker's circuitry.
Pacemaker leads may be positioned in the atrium, ventricle, or both, depending on the condition requiring the pacemaker to be inserted.
An atrial arrhythmia (an arrhythmia caused by a dysfunction of the sinus node or the development of another atrial pacemaker within the heart tissue that takes over the function of the sinus node) may be treated with an atrial permanent pacemaker whose lead wire is located in the atrium.
A ventricular arrhythmia (an arrhythmia caused by a dysfunction of the sinus node, an interruption in the conduction pathways, or the development of another pacemaker within the heart tissue that takes over the function of the sinus node) may be treated with a ventricular pacemaker whose lead wire is located in the ventricle.
It is possible to have both atrial and ventricular arrhythmias, and there are pacemakers which have lead wires positioned in both the atrium and the ventricle. There may be one lead wire for each chamber, or one lead wire may be capable of sensing and pacing both chambers.
An ICD has a lead wire that is positioned in the ventricle, as it is used primarily for fast ventricular arrhythmias.
Pacemakers that pace either just the right atrium or just the right ventricle are called "single-chamber" pacemakers. Pacemakers that pace both the right atrium and right ventricle of the heart and require two pacing leads are called "dual-chamber" pacemakers.
Pacemaker/ICD insertion is done in the hospital, either as a short-stay surgical procedure, or in the cardiac catheterization or electrophysiology laboratory. The child is given medication to help him/her relax during the procedure.
In older children and teenagers who receive a transvenous pacemaker, a small incision is made just under the collarbone. The pacemaker/ICD lead(s) is inserted into the heart through a blood vessel which runs under the collarbone. This procedure is usually performed in the catheterization laboratory.
In younger children, the pacemaker may be placed into the abdomen through a small incision. A second incision is made in the chest to visualize the heart. The lead(s) are guided to the heart, then placed on the heart's surface. This procedure is usually performed in the operating room. Once the procedure has been completed, the child goes through a recovery period of several hours and often is allowed to go home the day after the procedure.
After receiving a pacemaker or ICD, you will receive an identification card from the manufacturer that includes information about your child's specific model of pacemaker and the serial number. You should carry this card with you at all times so that the information is always available to any healthcare professional who may have reason to examine and/or treat your child. A medical identification bracelet or necklace can also be worn by your child to alert others about the pacemaker or ICD in case of emergency.
Your child should wear a medical identification bracelet or necklace to let others know about the pacemaker in case of emergency. When he/she is old enough to have a wallet, it is a good idea to also carry an ID card that states he/she has a pacemaker.
In the past, people with pacemakers risked interference with the proper functioning of their pacemakers if they were too close to many items common in the everyday environment. However, with improvements in pacemaker technology, some of these issues are no longer of major concern.
According to The American Heart Association and pacemaker manufacturers, the following items have not been shown to alter the function of today's pacemakers:
- Microwave ovens
- Kitchen appliances such as blenders, toaster ovens, and electric knives
- Televisions (including the remote control), FM and AM radios, and stereos
- TV and radio transmitters
- Ham radios and CB radios
- Electric blankets and heating pads
- Electric shavers, hair dryers, curling irons, and other personal care appliances
- Gardening machinery, such as electric trimmers
- Garage door openers
- Metal detectors
- Copying and fax machines
- Properly grounded shop tools (except power generators or arc welding equipment)
Currently, cellular phones do not affect the functioning of pacemakers. Most pacemakers made today have a filter that allows the use of the majority of cellular phones used throughout the world, including analog and digital technologies. However, new frequencies are being made available for cellular phones by the Federal Communications Commission, and these new frequencies may make pacemakers less reliable. Studies are being done to investigate this further.
Make sure your child uses caution when going through security detectors at airports and government buildings such as courthouses. Pacemakers currently being manufactured should not be affected by these security devices, as long as its wearer moves through and away from the detector at a normal speed. Check with your child's physician about the safety of going through such detectors with your child's particular pacemaker. The metal in the pacemaker may activate a security alarm, however. Be prepared to show an identification card for the pacemaker or a medical identification bracelet in order to pass through security checkpoints.
The following situations may cause interference with pacemakers. (Some of the activities mentioned are not appropriate until a child nears adulthood, but may affect older teenagers.) Discuss the following in detail with your child's physician:
- Avoid working with, holding, or carrying magnets near the pacemaker.
- Avoid magnetic resonance imaging (MRI) machines or other large magnetic fields, since the pacemaker's performance can be affected. Also, metal objects are not permitted near MRI machines.
- Avoid diathermy (the use of heat in physical therapy to treat muscles).
- Turn off large motors, such as cars or boats, when working on them, as they may temporarily "confuse" the pacemaker's rate. Do not use chain saws, because of the close contact with the motor components.
- Avoid certain high-voltage or radar machinery, such as electric arc welders, high-tension wires, radar installations, smelting furnaces, electric steel furnaces, and other high-current industrial equipment. Avoid working in restricted spaces near radio or television transmitting towers and antennas.
- If your child is having a surgical procedure performed by a surgeon or dentist, tell the surgeon or dentist that your child has a pacemaker, so that electrocautery will not be used to control bleeding (the electrocautery device can change the pacemaker settings).
- Certain medical procedures may occasionally affect the function of the pacemaker, but might be performed successfully with some adjustments to the pacemaker settings. These procedures include the following:
- Extracorporeal shock-wave lithotripsy (ESWL) - a procedure that dissolves kidney stones
- Radiofrequency ablation - a procedure that uses radio waves to control irregular heart rhythms
- Transcutaneous electrical nerve stimulation (TENS) - a device used to relieve acute or chronic pain
- Therapeutic radiation treatments for cancer
Consult your child's physician before your child undergoes these procedures.
Your child may also have to take antibiotic medication before any medically-invasive procedure to prevent infections that may affect the pacemaker.
Always consult your child's physician if you have any questions concerning the use of certain equipment near your child's pacemaker.
Once the pacemaker has been implanted, children with pacemakers should be able to do the same activities everyone else in their age group is doing: living normally.
However, when involved in a physical, recreational, or sporting activity, a child with a pacemaker should avoid receiving a blow to the skin over the pacemaker. A blow to the chest or abdomen near the pacemaker can affect its functioning. Contact sports are usually not recommended for children with pacemakers for this reason. If your child does receive a blow to that area, contact your child's physician. Consult your child's physician for activity restrictions.
Always consult your child's physician when he/she feels ill after an activity, or when you have questions about beginning a new activity.
Although your child's pacemaker is built to last several years, always check the pacemaker regularly to ensure that it is working properly. The proper method for checking the accuracy of your pacemaker includes the following:
- Take your child's pulse regularly to make sure the pacemaker is keeping your child's pulse at the targeted rate.
- Participate in a telephonic check-up for your child's pacemaker on a periodic basis. Your child's physician will provide special instructions.
- See your child's physician regularly for check-ups.
- Report any unusual symptoms or symptoms similar to those your child had prior to the pacemaker insertion to your child's physician immediately.
Always consult your child's physician for more information, if needed.