by Julie B. Shea, NP
Brigham and Women's Hospital, Boston
What is a pacemaker?
A pacemaker is a small device that is used to regulate your heart rhythm. The pacemaker system, which consists of a battery pack (pulse generator) and either one of two wires (leads), is surgically implanted under the skin in your chest, just beneath your collarbone. The pacemaker continuously monitors (senses) your heart's natural rhythm and will stimulate the heart to beat (paces) when it senses that your own heart rhythm is too slow. It will stimulate your heart to beat in a way that mimics your heart's own electrical beat. The electrical signal that is sent from the pacemaker is strong enough to stimulate the heart to beat, but not strong enough for you to feel.
Why do I need a pacemaker?
Your heart, like a mechanical pump, needs some electrical source to drive it. Your heart has its own electrical system (cardiac conduction system) that stimulates your heart to beat. The electrical signals originate in the upper right chamber (atria) of the heart in a region called the sino-atrial or "SA" node. The SA node regularly fires electrical signals to stimulate the heart to beat. The normal SA node fires at an average rate of 60-80 beats per minute. The SA node can increase the frequency of the signal, such as during exercise, to speed up the heart rate in order to meet the body's increased metabolic demands.
Once the signal leaves the SA node, it travels through both the upper chambers of the heart (atria) causing the atria to mechanically contract and squeeze blood in to the lower pumping chambers (ventricles) . While the mechanical contraction is occurring, the electrical signal passes through a region in the middle of the heart called the atrio-ventricular or AV node. The impulse then continues down the specialized pathway to the lower pumping chambers (ventricles) causing them to contract and squeeze blood out to the body and lungs. Each signal that passes through the conduction system results in one heartbeat. (figure 1)
Figure 1: heart's normal conduction system
Any interruption in the normal flow of the electrical signal through the cardiac conduction system can cause an abnormality in the heart's rhythm.The SA node can "slow down" as the result of the normal aging process. This can cause the heart to beat too slowly or fail to accelerate the heart rate with normal activity/exercise. The condition is called "sick sinus syndrome ". The slowly beating heart does not circulate enough blood to meet the metabolic needs of the body and resultantly can cause fatigue, activity intolerance, or potentially even loss of consciousness (syncope).
Interruption of the electrical signal in the region of the AV node is called "heart block ". (figure 2) The AV node is the only electrical connection between the upper chambers (atria) and the lower chambers (ventricles). Heart block occurs when the electrical signal is either significantly delayed or can not pass through the AV node to the lower pumping chambers. Heart block can also be the result of an aging cardiac conduction system or can be related to certain medications or cardiac surgical procedures. There are varying digress of heart block that can occur. The ventricles, unless stimulated by a normal signal, can only generate a heart rate of 20-40 beats per minute on their own. In this situation, the heart rate is much too slow to meet the normal demands of the body. Most individuals who develop significant heart block feel poorly and may pass out. The pacemaker will maintain the heart rate within the normal range according to your specific needs.
Figure 2: heart block
What is a pacemaker system?
A pacemaker system is a two part electrical system comprised of a pulse generator and either one or two leads.
The pulse generator is a small implantable device that is approximately the size of four stacked half dollar coins. Inside it's metal shell, the pulse generator contains the electronic circuitry, which continuously analyzes the heart's rhythm and regulates the pacemaker function, as well as a lithium battery that provides the power source for the device. (figure 3)
The leads are thin insulated wires that are implanted inside the heart muscle in either the right atria, the right ventricle, or in both chambers. The leads receive electrical information from the heart (sensing) as well as transmit electrical impulses to the heart to stimulate it to beat (packing).
Figure 3: pulse generator and pacing leads
Types of pacemakers
Single chamber pacemakers are pacing systems that use one lead in either the right atrium or the right ventricle of your heart.
A single lead in the right atrium is commonly used in conditions where the normal pacemaker of the heart is not working adequately, such as in the case of sick sinus syndrome. Atrial pacing is used when the sinus node is sending out signals that are too slow or irregular. However, to use this method of pacing, the rest of the heart's normal conduction system must be functioning normally. (figure 4)
More commonly, the single lead is placed in the right ventricle to help correct a slow or irregular heart beat. This is most often the case when the electrical flow is slowed or blocked in the region of the atrio-ventricular (A-V) node and the normal impulses from the atria cannot reach the ventricle. This would result in too slow a heart beat. The pacemaker system would keep the heart beating at a steady rate. (figure 5)
Figure 4: AAI Pacing System
Figure 5: VVI Pacing System
Dual chamber pacemakers are pacemaker systems that use a lead in the right atrium as well as the right ventricle (figure 6). This type of pacing most closely mimics the heart's normal conduction pattern by pacing sequentially from atria to ventricle thus maximizing the heart's pumping ability. By having a lead in both the atria and ventricle the pulse generator is able to continuously regulate the heart's electrical activity in both chambers. These are the most commonly used pacemakers at the present time.
Figure 6: dual chamber pacemaker
Rate responsive pacemakers can be incorporated into either single chamber or dual chamber pacing systems. The normal heartbeat fluctuates during the course of 24 hours depending upon your activity. During sleep, the heart rate normally slows. During times of activity or stress, however, the heart rate normally speeds up to meet the increasing demands on the body. Individuals with the abnormality of the conduction system may be unable to properly speed up the heart rate during activity. This can result in fatigue, shortness of breath and/or activity intolerance. Rate responsive pacemakers have special sensors built into the pulse generator that can sense increasing activity by means of increased body movement (vibrations) and/or increased rate of breathing. The sensors will automatically increase or decrease your heart rate according to your body's needs. Your pacemaker physician can "fine tune" the sensor(s) to meet your individual needs according to your level of daily activity. Rate responsive pacing most closely mimics the normal heart beat. (figure 7)
Figure 7: heart rate during different activities
How is a pacemaker implanted?
Implantation of a pacemaker requires a surgical procedure that is generally performed by an electrophysiologist, who is a specialized cardiologist or a surgeon. A small incision (2-3 inches) is made under your collarbone either on the right or left side of your chest. Depending on the type of pacemaker system you need, either one of two leads will be placed through a large vein under your collarbone and threaded down the inside of your heart. The physician implanting your device uses a special type of x-ray (fluoroscopy) to position the leads inside your heart. The leads are attached to the inner surface of the heart muscle by either a small corkscrew (active fixation) or a tined tip (passive fixation). Electrical measurements of the lead(s) position are performed to ensure a proper location and fixation.
Once the lead(s) are positioned inside your heart muscle, the physician will then create a small pocket or space to fit the pulse generator under the skin of your chest. The lead(s) are then plugged in to the pulse generator and firmly tightened in place. The pulse generator is then placed in to the pocket and the skin is sutured (sewn) back together. A dressing is placed over the operative site to keep it clean. As with most surgical procedures, antibiotics are generally given before and after your pacemaker implantation to decrease the likelihood of infection.
What are the potential complications associated with implantation?
As with any surgical procedure, there are some potential risks associated with implantation of a pacemaker. Your physician will discuss these potential risks with you prior to your pacemaker surgery. Overall, having a pacemaker implanted is considered a safe procedure to undergo.
What is the recuperative time after having a pacemaker implanted?
Recovering from pacemaker surgery is rather quick. You may either go home the same day, or most patients spend one night in the hospital following the procedure. There may be some minor discomfort following the procedure. Tylenol or other over-the-counter pain relief medications can be used as needed. Most individuals feel fine within a few days. Stronger pain medication can be prescribed as needed based upon your level of discomfort.
As with any surgical incision, you should avoid getting the pacemaker site wet for at least 48 hours. If you notice any swelling, tenderness, or warmth at the pacemaker site, you should call your physician or nurse as soon as possible.
When you return home you can resume most of your normal activities. The time frame in which you return to work will of course depend on your occupation. You should discuss these issues with your physician.
Certain activities are to be avoided, especially during the first four weeks after pacemaker implantation. Caution should be taken in regards to excessive arm movement on the side where your pacemaker was implanted. You should avoid vigorous activities such as golf or tennis for 4-6 weeks after the implant. It is also recommended that you avoid any heavy lifting (over 10lbs/22Kg) for this time frame as well. This is to avoid potentially dislodging one of the pacing leads.
Commonly asked questions about pacemakers
Will I need to make any lifestyle changes after my pacemaker is implanted?
There are no significant lifestyle changes that you will need to make as a result of having a pacemaker implanted. Most patients resume their normal activities soon after implantation. Specific issues or concerns should be addressed with your pacemaker physician or nurse.
How often will I need to have my pacemaker checked?
Your pacemaker system will need to be evaluated by your pacemaker physician, nurse, or your local cardiologist's office at least twice yearly. A special computer called a programmer is used to perform a comprehensive evaluation of your pacemaker system. The programmer has a wand (like a computer mouse) that is used to communicate with the pacemaker. The wand is placed on your chest directly over the pulse generator and a radio wave signal is used to send and receive information from the pulse generator. Changes in the pacemaker settings can be done via this method as well. A complete assessment of the pacemaker's sensing and pacing functions, battery life, and diagnostic information is obtained, which enables your pacemaker physician/nurse to fine tune your care.
In addition to routine office visits, you may be asked to check your pacemaker system over the telephone - what is known as trans-telephonic monitoring. You will be provided with a small monitoring device that is used to transmit your electrocardiogram over the telephone to a receiver station at your doctor's office or a commercial pacemaker monitoring service. This type of monitoring is performed on a defined schedule - usually every 8 weeks or so. The purpose of trans-telephonic monitoring is to closely monitor the battery life of the pulse generator as well as to identify any potential sensing or pacing abnormalities.
How is the battery changed?
The battery that is used to power your pulse generator is tightly sealed within the metal shell of the device. Therefore, when the battery's energy is depleted a whole new pulse generator must be implanted. The skin over the pulse generator site is numbed up with local anesthetic. You may also receive a light sedative through a intravenous line to help you relax. A new incision is made in the skin and the pacemaker pocket is opened. The pulse generator is removed and lead(s) disconnected. At this time the lead(s) are hooked to a special analyzer that evaluates the lead(s) for any evidence of potential malfunction. A new pulse generator is then attached to the lead(s) and the system is reimplanted in the same pocket. The incision is sutured (sewn) together and a small dressing applied. Most patients can go home the same day as their procedure.
Can I use a microwave?
Microwave ovens will not interfere with the proper functioning of your pacemaker. You can use a microwave oven without concern.
Can I use a cell phone?
It is possible that a cellular phone might interfere with the normal functioning of your pacemaker. The interaction is temporary, however, and will only affect the pacemaker during the time that your cellular phone is close to your pacemaker. To avoid this potential interference, it is recommended that you hold the cellular phone on the opposite side of your body away from the pacemaker. You should also not store your cellular phone in your breast pocket.You should always try to maintain a distance of at least 6 inches between your cellular phone and your pacemaker system.
Do I have to take any precautions at the airport?
If you were to walk through the metal detector at the airport, it will not harm you nor your pacemaker. However, because the pacemaker is encased in a metal shell, it is possible that the pacemaker may set off the security alarm. To avoid this problem, it is generally recommended that you show your pacemaker identification card to the security agent and inform him/her that you have an implanted pacemaker system. They should let you pass around the metal detector. If the airport security wants to scan you with the "hand wand", they can everywhere except over the device. This information also pertains to any metal detector such as at a courthouse or federal building.
You should also be thoughtful when passing through the anti-theft gates at local stores. It is alright to pass through the gate, however, you should not stand directly next to the gate. It is possible that the electronic impulses from the security gate may interfere with your normal pacemaker function.
Will any other electronic equipment interfere with my pacemaker?
Some types of industrial equipment, such as arc welders, may potentially interfere with your pacemaker's normal function. If you work in an environment where heavy industrial equipment is used, you should speak with your pacemaker physician regarding potential interactions.
Certain types of hospital equipment, such as magnetic resonance imager (MRI), can interfere with your pacemaker function. If obtaining an MRI were felt to be critical to your care, this would require discussion between you, your pacemaker physician, and the physician ordering the MRI.
Is there a chance my pacemaker might fail?
There is a remote possibility that your pacemaker system might fail. However, the technological advances that have been made in pacemaker technology make this unlikely.
Future applications of pacemaker technology
Although pacemakers are primarily used for disorders of slow heart beating, they are now being looked at to treat other heart conditions. Specialized pacemakers, which use a three-lead system, are under evaluation to determine whether or not biventricular (right and left ventricle) pacing will improve the pumping ability of a weakened heart muscle in patients with heart failure. Additionally, the use of pacemaker technology is being developed to treat other heart rhythm disturbances such as atrial fibrillation. For more information on these topics, please refer to the atrial fibrillation and heart failure sections of this website.
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This page was last modified on 9/18/2015