Patient education: Pacemakers (Beyond the Basics)

INTRODUCTION — 

Pacemakers are electronic devices that stimulate the heart with electrical impulses to maintain or restore a normal heartbeat. This topic review will discuss pacemakers, when they may be necessary or appropriate, the types of pacemakers that are available, and the precautions patients need to take after having a pacemaker placed.

THE HEART'S CONDUCTION SYSTEM AND "NATURAL PACEMAKER" — 

The heart has its own built-in electrical system, called the conduction system (figure 1). The conduction system sends electrical signals throughout the heart that determine the timing of the heartbeat and cause the heart to beat in a coordinated, rhythmic pattern. The conduction system stimulates precise contractions of the heart's chambers to ensure that blood is pumped effectively.

The electrical signals, or impulses, of the heart are generated by specialized tissue called the sinoatrial (SA) or sinus node (figure 1). The sinus node is sometimes called the heart's "natural pacemaker." Each time the sinus node generates a new electrical impulse; that impulse spreads out through the heart's upper chambers, called the right atrium and the left atrium (figure 2). This electrical impulse stimulates the atria to contract, pumping blood into the lower chambers of the heart (the right and left ventricles).

The electrical impulse then spreads to another area of specialized tissue located between the atria and the ventricles, the atrioventricular (AV) node. The AV node momentarily slows down the spread of the electrical impulse, to allow the left and right atria to finish contracting.

From the AV node, the impulse spreads into a system of specialized fibers called the bundle of His and the right and left bundle branches (figure 1). These fibers distribute the electrical impulse rapidly to all areas of the right and left ventricles, stimulating them to contract in a coordinated way. With this contraction, blood is pumped from the right ventricle to the lungs, and from the left ventricle throughout the body.

ARRHYTHMIAS — 

The heart's conduction system must function normally for the heart to beat properly and to pump blood effectively to meet the body's needs. Problems with the flow of electrical impulses in the heart can cause heart rhythm disturbances known as "arrhythmias." This general term indicates an abnormality in the pattern of electrical activation of the heart.

Bradyarrhythmias — Bradyarrhythmias are heart rhythm abnormalities that cause the heart to beat too slow. Most bradyarrhythmias are due to one of two kinds of problems: sinus bradycardia or heart block.

Sinus bradycardia occurs when the heartbeat is too slow because the heart's "natural pacemaker" in the top right chamber (the right atrium) is operating too slowly. Although some people (for example, competitive athletes) may have a slow heartbeat as a result of good health, in others sinus bradycardia is an abnormal condition that may require treatment.

Heart block is a term for a delay or interruption in the heart's electrical wiring (the conduction system), causing the electrical impulses to travel too slowly, occasionally, or not at all. There are several kinds of heart block, classified according to location (where in the conduction system the block occurs) and degree (whether the block is mild, causing delayed conduction, or severe, causing conduction to stop).

●In first-degree atrioventricular (AV) block, all electrical impulses reach the ventricles from the atria, but are abnormally slowed as they pass through the AV node.

●In second-degree AV block, some atrial impulses fail to reach the ventricles ("dropped beats"), resulting in a slow or an irregular heart rate.

●In third-degree AV block, the most serious form, no atrial impulses are conducted to the ventricles. This condition is sometimes called complete heart block. For the heart to continue to beat, a separate electrical impulse (called an escape rhythm) may be generated in the ventricles. Without an escape rhythm, the ventricles (the chambers that pump blood throughout the body) stop beating.

●In right bundle branch block (RBBB), impulses are not conducted by the right bundle branch. Electrical impulses reach the right ventricle only by traveling through the heart muscle from the left ventricle. As a result, activation of the right ventricle is delayed.

●In left bundle branch block (LBBB), impulses are not conducted by the left bundle branch. Electrical impulses reach the left ventricle only by traveling through the heart muscle from the right ventricle. As a result, activation of the left ventricle is delayed.

Arrhythmia symptoms — Symptoms of arrhythmias vary depending upon the specific arrhythmia and other factors, especially if there is underlying heart disease. While some people have no symptoms, others do have symptoms, which may include:

●Fainting episodes (syncope) (see "Patient education: Syncope (fainting) (Beyond the Basics)")

●Dizziness or lightheadedness (a feeling like you might pass out)

●Palpitations (a sensation of the heart pounding)

●Confusion

●Extreme fatigue

●Shortness of breath

●Impaired ability of the heart to pump enough blood to meet the body's needs (heart failure)

The decision to treat an arrhythmia with a pacemaker (or any other treatment) depends in part upon whether the person has symptoms or not as well as the severity of the symptoms. In some cases, the heart rate is simply too slow, and a pacemaker is needed to effectively pump the blood out of the heart.

Underlying causes — A variety of conditions can lead to the development of cardiac arrhythmias. Some of the more common causes include:

●Coronary artery disease, where there is a malfunction or damage of the heart due to narrowing or blockage of arteries supplying blood to heart muscle. This damage is known as a myocardial infarction or "heart attack."

●Certain structural heart malformations present at birth (congenital heart defects).

●Inherited genetic abnormalities that are not necessarily associated with a structural problem of the heart, but may result in an arrhythmia (such as the long QT syndrome).

●Abnormalities in the control and regulation of the heart rate and vascular tone by the nervous system, leading to fainting (called neurocardiogenic syncope).

●Diseases of heart muscle tissue, called cardiomyopathies. (See "Patient education: Hypertrophic cardiomyopathy (Beyond the Basics)".)

●Therapy with certain medications that may alter the heart's normal rhythm.

●Aging of heart muscle.

TEMPORARY AND PERMANENT PACEMAKERS — 

Artificial pacemakers are electronic devices that stimulate the heart with electrical impulses to maintain or restore a normal rhythm in people with slow heart rhythms. There are many situations in which an artificial pacemaker may be recommended.

Most commonly, a pacemaker is used for a slow heart rate (bradyarrhythmia) as described above. The decision to use such a device, as well as which specific type, will depend upon multiple factors, including:

●The exact nature and underlying cause of the arrhythmia

●Whether the condition is temporary or permanent

●The presence or absence of symptoms as described above

●The anticipated frequency of pacing

●The underlying cardiac conditions

How they work — An artificial pacemaker provides an electrical impulse (or "discharge") that can stimulate the heart, thus restoring or maintaining a regular heartbeat. Although various types of artificial pacemaker devices are available, they generally include the following components:

●A thin metal box or case called a pulse generator (picture 1) contains the power source producing electrical impulses to stimulate the heart muscle. The pulse generator also contains a small computer processor that can be programmed to set the rate of the pacemaker, the pattern of pacing, the energy output, and various other parameters. Signals are often sent through a device to the clinician's office to report on how well the pacemaker is working ("remote monitoring").

The pulse generator for most modern permanent pacemakers weighs between one to two ounces. (See 'Types of pacemakers' below.)

●Flexible insulated wires, known as leads, carry electrical impulses from the generator to the heart muscle and relay information concerning the heart's natural activities back to the pacemaker. There may be several such wires, or leads, placed within the heart, most commonly in the right atrium and right ventricle.

One type of pacemaker is "leadless" and does not have any wires. The pacemaker is a small device that is placed inside the heart and weighs less than one-tenth of an ounce.

●The pacing lead most commonly incorporates one or two electrical "poles." An electrical impulse is transmitted to the heart muscle when needed, and the lead is also able to sense the heart's own electrical activity.

Types of pacemakers — A variety of types of pacemakers and modes of pacing have been developed to restore or sustain a regular heartbeat in different ways:

●Some pacemakers sense the heart's own electrical activity and stimulate the heart only when the heart rate falls below the programmed pacing rate.

●Others stimulate the heart on a regular basis to "resynchronize" the electrical response and to improve the heart's ability to pump blood.

Pacemakers also have the capability to provide a change in heart rate as required ("rate response"). This depends on a "sensor" incorporated into the pacemaker that can sense activity, respiratory rate, or other parameters and can alter the heart rate based on the perceived physiologic need.

Temporary pacemakers — Temporary pacemakers are intended for short-term use during hospitalization. They are used because the arrhythmia is expected to be temporary and eventually resolve, or because the person requires temporary treatment until a permanent pacemaker can be placed.

The pulse generator of a temporary pacemaker is located outside the body and may be taped to the skin or attached to a belt or to the patient's bed.

Patients with temporary pacemakers are usually hospitalized and continuously monitored. Members of the health care team will perform regular examinations to monitor for any possible complications.

Permanent pacemakers — Permanent pacemakers are pacemakers that are intended for long-term use and are implanted inside the body.

Indications — Specific guidelines have been established concerning the conditions when a permanent pacemaker is (I) definitely beneficial, useful, and effective, (II) may be indicated, or (III) is not useful or effective and, in some cases, may be harmful. Patients should speak with their health care provider concerning these guidelines and how they apply to their specific case.

As a general rule, permanent pacing is recommended for certain conditions that are chronic or recurrent and not due to a transient cause. Permanent pacing may be considered necessary or appropriate for certain people with symptomatic bradyarrhythmia or, less commonly, to help prevent or terminate tachyarrhythmia.

Implantation — Before the pacemaker implantation procedure, your doctor may request that you temporarily stop taking some medications such as blood thinners or medications for diabetes. You may also need to make some changes to your medicines for a few days after the pacemaker is implanted.

Antibiotics are generally given at the time of the pacemaker implantation. It is important to make sure that you report any allergies to antibiotics or other medications before having the pacemaker implanted.

Generally the pacemaker is implanted in a sterile laboratory or operating room by a specialist (cardiologist, surgeon, or cardiac electrophysiologist) with experience in this procedure. Local anesthesia and often conscious sedation are used to make the procedure as pain-free as possible. General anesthesia is rarely required. The position of the pacemaker leads is usually checked using X-ray imaging (called fluoroscopy). The length of the procedure depends upon the type of device being placed.

Pacemakers with leads

●Pulse generator location – The pacemaker pulse generator is most commonly implanted into soft tissue beneath the skin in an area below the clavicle, which is known as prepectoral implantation (figure 3); this is located under the skin and fat tissue but above the pectoral muscle. The pacemaker leads are typically inserted into a major vein (transvenously) and advanced until the leads are secured within the proper region(s) of heart muscle. The other ends of the leads are attached to the pulse generator (figure 3).

Less commonly, the pulse generator is placed under the skin of the upper abdomen.

●Lead location

•A single-chamber pacemaker lead is placed in the right atrium or the right ventricle. This type of pacemaker is used for patients with specific medical problems that require only one lead.

•A dual-chamber pacemaker system most commonly includes one lead to the right atrium and one lead to the right ventricle.

•Leads to improve cardiac synchrony – The heart beats more efficiently when the walls of the left ventricle contract simultaneously and in sync with the right ventricle. Pacing leads can enhance cardiac synchrony in two ways:

-Cardiac resynchronization therapy (CRT) – For CRT, there is typically one lead in the right atrium and one in the right ventricle. The third lead is placed in a branch of the vein known as the "coronary sinus" and wraps around the back part of the left ventricle. Special techniques such as angiography are needed to locate the best spot to place the third lead.

-Conduction system pacing involves placing the right ventricular lead so that it captures part of the conduction system. This avoids the need for CRT and a third lead. This is a way to enhance cardiac synchrony during pacing.

Leadless pacemaker — Leadless pacemakers are generally implanted through a leg vein and placed directly in the heart muscle without the need for pacing leads. Leadless pacemakers are generally single-chamber in the right ventricle, but some newer types of leadless pacemakers allow for pacing in both the right atrium and right ventricle.

Recovery — Recovery from the procedure is rapid, but there may be some restrictions on arm movement and activities for the first two to four weeks. Depending on how the incision is closed, you may need to keep the area clean and dry for several days as it heals. Frequently, a wound check is required 7 to 10 days after the pacemaker is implanted.

Lead dislodgment is more common in the first few weeks after implantation. The hospital stay is usually brief, and the procedure can be performed as an outpatient. Uncommon but possible risks associated with permanent pacemaker implantation include collapsed lung (pneumothorax), infection, perforation/tamponade, lead dislodgment, and bleeding.

Once implanted, pacemakers can be programmed to change the baseline heart rate, the upper heart rate at which the pacemaker will pace, and heart rate changes that should occur with exercise.

Follow-up care — People who have a permanent pacemaker will require periodic surveillance of the implanted device. The status of the pacemaker will be regularly checked or "interrogated" (often done remotely, generally using a secure web-based system) to provide information regarding the type of heart rhythm, the functioning of the pacemaker leads, the frequency of utilization of the pacemaker, the battery life, and the presence of any abnormal heart rhythms.

All contemporary devices are programmable with information and settings that can be altered and stored. Information is obtained by transmitting data from the pulse generator to a programmer, usually done during a follow-up office visit. However, with newer pulse generators it may be possible to obtain information about the pacemaker's performance by downloading data from the patient's device to the internet and then to the caregiver's office. In older devices, pacemaker status can be checked routinely via the telephone using a trans-telephonic device.

The pulse generators are usually powered by lithium batteries that function for an average of over 10 years before they need to be replaced. However, there is variability depending upon the amount of energy required to pace and the number of leads that are placed. When pacemaker batteries wear out, they do so in a very slow and predictable fashion, allowing sufficient time to be detected and pulse-generator replacement planned. Replacing the pulse generator usually requires a procedure in which a skin incision is made over the old incision, the old generator is removed, and a new generator is implanted and joined with the existing leads, assuming the existing leads are functioning normally.

The pacemaker leads are usually used indefinitely, unless a specific problem occurs (eg, the lead loses contact with the heart, the lead breaks, the insulation is damaged, or the lead is not functioning properly). In such circumstances, the lead may require replacement. Often, the old lead is left in place but disconnected from the pulse generator and capped, and a new lead is inserted. Removal of an old lead is feasible but difficult in most cases, because of the formation of scar tissue binding the lead to the blood vessels and heart muscle. Lead removal is usually necessary if the system becomes infected.

AVOIDING ELECTROMAGNETIC INTERFERENCE — 

Although contemporary pacemakers are less susceptible to interference than older models, electromagnetic energy can interfere in some cases. Thus, experts advise that people with pacemakers be aware of the following:

Household appliances — Pacemaker manufacturers do not recommend any special precautions when using normally functioning common household appliances such as microwave ovens, televisions, radios, toasters, and electric blankets.

Cellular phones — People with a pacemaker or a defibrillator should know that items with strong magnetic fields (eg, cellular phones with magnets for wireless charging [iPhone 12], magnetic accessories such as certain “smart watches”) can affect the function of the device if they are very close (less than six inches) to their device. Cell phones without strong magnets are unlikely to cause problems with pacemakers or defibrillators.

If you have a pacemaker or a defibrillator, the safest strategy is to use your cell phone at the ear on the side opposite the cardiac device. When you are carrying your phone, keep it in a pocket or bag below your waist. If you’re not sure whether your phone or watch is likely to cause problems with your cardiac device, check with the manufacturer or your doctor.

Anti-theft systems — Electromagnetic anti-theft security systems are often found in or near the workplace, at airports, in stores, at courthouses, or in other high-security areas. Although interference with a pacemaker is possible, it is unlikely that any clinically significant interference would occur with the transient exposure associated with walking through such a field. Based upon several studies and observations, experts advise that patients with pacemakers should:

●Be aware of the location of anti-theft systems and move through them at a normal pace

●Avoid leaning on or standing close to an anti-theft system

Metal detectors at airports — Similar to antitheft systems, metal detectors at airports can potentially interfere with pacemakers, although this is unlikely. Such exposure has been shown to cause interference in some cases and may be related to the duration of exposure and/or distance between the security system and the pacemaker. Metal detectors will likely be triggered by the presence of a pacemaker and therefore at places such as airports, it will be important for individuals with pacemakers to carry an identification card for their pacemaker, and airport personnel will likely prefer to do a manual search.

External electrical equipment — External electrical fields do not seem to cause a problem for most people with a pacemaker. However, in workplaces that contain welding equipment or strong motor-generator systems, because interference can inhibit pacing, it is recommended that a person with an implanted cardiac device remain at least two feet from external electrical equipment, verify that the equipment is properly grounded, and leave the immediate locale if lightheadedness or other symptoms develop.

Diagnostic or therapeutic procedures — Certain types of surgery and procedures may interfere with pacemakers. Most importantly, the use of electrocautery can inhibit pacemaker function. It is not uncommon therefore that a pulse generator may require specific reprogramming before the procedure and programming back to its baseline condition after the procedure. In some instances, a magnet is all that is required on the device to make sure that there is no problem with the device during the procedure. Such procedures include:

●Magnetic resonance imaging (MRI) uses a strong magnetic field that is pulsed on and off at a rapid rate. In the past, this procedure was a relative contraindication for patients with a pacemaker. However, with the introduction of specialized pacemakers that are "MRI safe," MRI scans can be performed. Nevertheless, specialized programming may be required during the MRI scan and the pacemaker may be checked after the procedure. Even patients with a standard pacemaker (ie, not designated "MRI safe") can often undergo MRI scans with careful monitoring and other appropriate precautions.

●Transcutaneous electrical nerve/muscle stimulators (TENS), a method of pain control.

●Diathermy, which heats body tissues with high-frequency electromagnetic radiation or microwaves.

●Extracorporeal shock wave lithotripsy, the use of sound waves to break up gallstones and kidney stones.

●Therapeutic radiation for cancer or tumors, which can cause permanent pacemaker damage.

●Any surgery in which electrocautery is being used. The risks are greatest when the electrocautery is being performed close to the pulse generator.

Thus, doctors, dentists, and other health care providers should be informed about a person's pacemaker. If a procedure associated with pacemaker interference is contemplated, the possible benefits, risks, and alternatives should be considered and discussed, as appropriate. People with pacemakers should carry a medical identification card for emergencies.

WHERE TO GET MORE INFORMATION — 

Your health care provider is the best source of information for questions and concerns related to your medical problem. The manufacturer of your device likely also has a patient call line, and the number would be listed on your identification card.

This article will be updated as needed on our website (www.uptodate.com/contents/table-of-contents/patient-information). Related topics for patients, as well as selected articles written for health care professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Pacemakers (The Basics)
Patient education: Pacemaker insertion (The Basics)
Patient education: Pacemaker check (The Basics)
Patient education: Implantable cardioverter-defibrillators (The Basics)
Patient education: Catheter ablation for the heart (The Basics)
Patient education: Cardiac resynchronization therapy (The Basics)
Patient education: Bradycardia (The Basics)
Patient education: Sinus node dysfunction (The Basics)
Patient education: Long QT syndrome (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Implantable cardioverter-defibrillators (Beyond the Basics)
Patient education: Atrial fibrillation (Beyond the Basics)
Patient education: Syncope (fainting) (Beyond the Basics)
Patient education: Hypertrophic cardiomyopathy (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Cardiac implantable electronic device interactions with electromagnetic fields in the nonhospital environment
Cardiac resynchronization therapy and conduction system pacing in heart failure: System implantation and programming
Cardiac resynchronization therapy in systolic heart failure: Indications and choice of system
Permanent cardiac pacing: Overview of devices and indications
Infections involving cardiac implantable electronic devices: Epidemiology, microbiology, clinical manifestations, and diagnosis
Modes of cardiac pacing: Nomenclature and selection
Pacing system malfunction: Evaluation and management
Temporary cardiac pacing
Sinus node dysfunction: Treatment

The following organizations also provide reliable health information.

●National Library of Medicine

(www.medlineplus.gov/pacemakersandimplantabledefibrillators.html, available in Spanish)

●National Heart, Lung, and Blood Institute

(www.nhlbi.nih.gov/health/dci/Diseases/pace/pace_whatis.html)

●American College of Cardiology

(www.acc.org)

●American Heart Association

(www.heart.org)

●Heart Rhythm Society

(www.hrsonline.org/patient-resources)

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ACKNOWLEDGMENT — 

The UpToDate editorial staff would like to thank David L Hayes, MD, and Leonard Ganz, MD, FHRS, FACC, who contributed to earlier versions of this topic review.