Pacemakers are life-saving devices used to assist the electrical activity of a patient’s heart rhythm. Pacemakers — temporary or permanent — sense a patient’s heart activity and produce an electrical stimulus (pace) when the heart fails to beat on its own. This electrical impulse creates a myocardial contraction to assist the patient’s own rhythm.

Implanted permanent cardiac pacemaker systems have been used since 1960^1,2 with technological advances over the years resulting in smaller units and dual-chamber and multiprogrammable pacemakers. About 300,000 people in the U.S. receive a permanent pacemaker each year, and about 900,000 pacemakers are implanted worldwide.^3,4

The geriatric population is the fastest-growing group in the U.S., and patients older than 70 account for more than 70% of pacemakers implanted.^1,3,5 The risk that the heart’s conduction system will become dysynchronous increases with age, resulting in arrhythmias best managed with pacemaker therapy.^2-6 The use of pacemakers is expected to increase as the population continues to age. Given the aging of the population, it’s essential that nurses be knowledgeable about pacemakers and care requirements of patients with pacemakers.

Indications

In a healthy heart, an electrical impulse travels from the sinus node to the atrioventricular node, down the right and left bundle branches, and then to the Purkinje fibers, stimulating the myocardium to contract. Pacemakers help maintain this normal cardiac electrical activity by delivering electrical impulses when the intrinsic (the patient’s own) electrical system fails. Indications for pacemaker insertion include symptomatic bradycardia, second- and third-degree atrioventricular block, sinus node dysfunction, carotid sinus hypersensitivity, hypertrophic cardiomyopathy, chronotropic (rate) incompetency, and chronic heart failure.^1-8 The majority of pacemakers are placed to treat nodal dysfunction rhythms (sick sinus syndrome, sinus bradycardia, sinus arrest, and atrioventricular blocks) that result in symptomatic bradycardia.^1,2,5-8

Components

A pacemaker system consists of a pulse generator and lead(s). The pulse generator is the power source of the pacing system: It contains the electrical circuitry to stimulate the heart. A lithium-iodide battery powers the pulse generator and has an average life of seven to 10 years. Microprocessors in the generator control sensing and electrical output (voltage).^1,8 Sensitivity refers to the ability of the pacemaker to “see” intrinsic cardiac activity. The principle of sensitivity is important in that the pacemaker must be able to determine what electrical activity is intrinsic so that the pacemaker will not generate an electrical impulse inappropriately, creating myocardial contraction.

In addition to sensitivity, pacemakers have upper and lower intrinsic heart rate limits. If the pacemaker does not sense a heart rate (that is, if the intrinsic rate is lower than the set lower pacemaker rate), an electrical output will stimulate a myocardial contraction. Leads are the connection between the pulse generator and the myocardium; they are electrodes that are placed into the myocardium and adhere to the muscle tissue. Leads sense intrinsic cardiac function as well as providing an electrical stimulus for contraction. Leads may be bipolar or unipolar, referring to the number of electrodes placed on the lead that is implanted in the heart. Most systems today are bipolar, which have a cathode (negative pole) and an anode (positive pole) located at the tip of the lead that keeps the electrical circuit (current flow) within the heart. When the pacemaker stimulates a lead, a current flows from the cathode to stimulate the heart and then back to the anode to complete the circuit. Unipolar leads function similarly, but the anode is located on the surface of the pulse generator, thus creating a longer circuit for conduction. Inflammation at the tip of the lead can interfere with pacing.

One advance in lead technology is the use of a steroid-eluting lead that releases a small amount of steroid to reduce inflammation at the lead-myocardium interface, thereby improving pacing.^1,7,10 Correct placement of the lead and good contact of the lead with the myocardium are essential for proper pacing.

Implantation

Generally, the implantation of a pacemaker is considered minor surgery and can be either an inpatient or outpatient procedure. Risks associated with the procedure are related to the care of the incision site, infection, and pacemaker malfunction. A small incision (2 to 3 inches) is made in the subcutaneous tissue under the clavicle, creating a pocket in the chest overlying a muscle. The pulse generator is inserted into this tissue pocket. The pacemaker leads are introduced into a vein and advanced into the heart using fluoroscopy. The leads are secured to the cardiac muscle tissue and tested to ensure appropriate sensing threshold and capture of myocardial activity.

Sensing threshold is the minimum intracardiac electrical signal the pacemaker must sense to inhibit the pacemaker. In other words, when inhibited, the pacemaker does not pace because it senses that the patient’s heart had a beat. Capture refers to the pacemaker’s delivery of electrical energy to the myocardium, resulting in contraction. Finally, the leads are inserted into the pulse generator and secured.

Patient instructions after the implantation should include:^1-3,7,9

• Observe for signs and symptoms of infection at the pacemaker incision site (erythema, edema, pain, drainage, fever).
• Avoid lifting with the arm closest to the pacemaker (usually the left arm) for one or two months. Do not lift anything over 5 pounds (2.3 kg).
• Avoid wearing clothes that you must pull over your head.
• Observe for signs and symptoms of improper pacemaker function (shortness of breath, dizziness, syncope, fatigue, chest pain, persistent hiccups, and peripheral edema).
• Keep the incision clean and dry to allow the skin to completely heal (about five days).
• Don’t drive until your physician or cardiologist says it is OK.
• Always carry the pacemaker identification card, which informs people that you have a pacemaker.

Pacing modes

The ability of a pacemaker to sense intrinsic heart activity and produce an electrical stimulus if needed depends on how the device is programmed. The pacemaker can be programmed to sense intrinsic activity of the atria, ventricles, or both, and will deliver an electrical stimulus creating myocardial contraction (capture) of the atria, ventricle, or both. The physician will program the pacemaker to sense and capture the heart based on the underlying dysrhythmia (e.g., brady dysrhythmia) or clinical reason for pacemaker implantation.

Developed in 1974, the NASPE/BPEG generic (NPG) code standardized the description of a pacemaker system (program).^2,7,11 (NASPE stands for the North American Society of Pacing and Electrophysiology and BPEG for the British Pacing and Electrophysiology Group). The coding system has been modified to reflect changes in technology; however, consistency in the codes allows for a universal understanding of pacing modes. The table explains the standard pacemaker codes, with the letter in the first column corresponding to the first letter listed in a code, the second to the second, and so forth. Each letter represents the function of the pacemaker and several modes that are commonly used. The first letter describes which chamber(s) of the heart may be paced. The second letter represents which chamber(s) of the heart may be sensed for intrinsic activity. The third letter indicates the pacemaker response to the intrinsic cardiac activity. “Inhibited” indicates that intrinsic activity was sensed and the pacemaker will not produce a stimulus. “Triggered” represents pacemaker-generated impulses that have stimulated myocardial contraction. For example, a pacemaker with the programmed settings of VVI means the ventricle is paced, sensed, and inhibited by intrinsic activity. VOO indicates that the ventricle is paced and intrinsic heart activity is not sensed by the pacemaker, nor does it inhibit, or stop, pacing of the ventricle. (See ECG 1.) A dual-chamber pacemaker typically is programmed in the DDD mode. In this mode, both the atria and ventricle are paced and sensed, and intrinsic activity will inhibit and/or trigger pacemaker activity (ECG 2). A DDDR pacemaker is capable of altering the pacing rate based on the patient’s physiologic need, and it is often considered the most physiologic mode of pacing, that is, the mode most like the heart’s own healthy pacing.

Additional concepts related to pacing modes relate to rate limits. If the patient’s intrinsic rate falls below a set lower rate, the pacemaker will pace or adjust the rate until it is within normal limits; this is considered the pacemaker’s lower rate limit. The upper rate limit is the maximum rate a pacemaker will pace the myocardium. Atrioventricular interval is the time delay, in milliseconds, from the sensed or paced atrial contraction to the sensed or paced ventricular contraction. This is the PR interval of the pacemaker. Hysteresis is a pacing parameter that allows the intrinsic heart rate to fall below the set pacing rate before the pacemaker immediately initiates pacing. This principle allows the patient’s intrinsic rate to be sensed below the set lower rate limit. For example, if the lower rate limit is set at 70 bpm, hysteresis would allow the patient’s rate to drop to 60 bpm before pacing the patient at the rate of 70 bpm. The benefit of hysteresis is to give the patient’s own rhythm the opportunity to intrinsically increase heart rate, which is physiologically more beneficial, before the pacemaker is activated.

Rate modulation is a sensor-mediated rate-responsive pacing function in which the heart rate increases in response to various stimuli, thus simulating the body’s normal physiologic response to activity.^1,2 For example, as a patient exercises, a faster heart rate is needed to increase the cardiac output necessary for the activity. Rate modulation allows for the pacemaker to sense a change in activity and increases the heart rate to meet physiologic demands. Activity-responsive pacemakers have motion detectors built into the pulse generator and sense changes in minute ventilation, QT interval, temperature, venous oxygen saturation, or right ventricular contractility. Minute ventilation sensors are the most commonly used sensor modality for rate modulation pacemakers.^1,2 Voltage refers to the amount of electrical energy delivered from the pacing generator to the tip of the lead.

Assessment

A systematic approach is required to interpret pacemaker function through the analysis of an electrocardiogram tracing. The patient’s history, physical exam, and disease process provide important information about the status of the pacemaker. It is also important to review the programmed settings with the patient and the reasons for pacemaker implantation. A two-lead ECG is beneficial in the initial assessment of a pacemaker’s function. Most bedside ECG monitors will print two ECG lead views that may also be used for assessment of pacemaker function. Pacemaker-generated myocardial contractions will be depicted with a “pacer spike,” or vertical line, on the ECG graph paper before the atrial or ventricle contraction waveform. It is important to consider the following items when assessing pacemaker function by ECG analysis:^1,7

• Is the intrinsic activity present? Are there intrinsic P waves or QRS complexes?
• Are pacing artifacts (spikes) present? Atre they arial (A), ventricular (V), or both?
• What is the relationship of the P wave to the QRS?
• For every pacer spike, do you see a correlating atrial or ventricular waveform?
• What is the heart rate? What is the programmed pacing rate?

Intrinsic myocardial activity must be present to evaluate sensitivity.⁷ If the pacemaker is functioning correctly, the pacer will sense intrinsic activity and not deliver a pacemaker impulse for contraction. If the pacemaker is undersensing, pacemaker spikes occur at inappropriate times within the patient’s intrinsic rhythm (ECG 3). In other words, the pacer is not correctly “seeing” the patient’s intrinsic heart rate and is pacing inappropriately. Failure to sense may be due to myocardial ischemia, bundle branch block, battery failure, lead fracture, or incorrect pacemaker settings. With undersensing, there is a risk of the pacemaker delivering a stimulus during the refractory period of the intrinsic cardiac cycle. Therefore, if undersensing is assessed, the physician should be contacted and the pacemaker settings will need to be adjusted.

Failure to capture is present when the pacemaker generates an impulse but does not create, or capture, myocardial contraction. The ECG will record a pacemaker spike that is not followed by myocardial depolarization (ECG 4).

Loss of capture may be due to dislodgment or malposition of the lead, severe metabolic or electrolyte imbalances, myocardial ischemia, battery failure, or altered pacing threshold (volts).^1,7,12 Assessment of failure to capture needs to be related to additional assessment parameters of the patient (intrinsic and paced heart rate, vital signs, worsening cardiac failure symptoms, level of consciousness) and reported to the physician immediately.

Patient education

The nursing care of patients with pacemakers is similar whether the device is temporary or permanent. Nurses should provide information about the signs and symptoms of pacemaker malfunction and general care of the pacemaker.

Most people with pacemakers lead normal lives. However, pacemakers are electrically stimulated devices, and some precautions should be taken. Advances in pacemaker technology have made pacemakers less sensitive to some environmental signals but more sensitive to others. Most household appliances, such as microwaves and tools, do not interfere with pacemaker function. But there have been a few reports of hair dryers, digital pagers, and digital cellular phones creating a static magnetic field that interfered with pacemaker function. Keeping these devices 6 inches away from the pacemaker should ensure safety.^2,10,12-14

Cordless and digital cellular phones may cause interference with pacemaker signals. The patient shouldn’t place the phone near the pacemaker (such as in a shirt pocket lying over the pacemaker) and should listen with the ear opposite the pacemaker (e.g., the right ear).^2,10-13

Advances in digital technology have created a competition in the signals the pacemaker may sense. Patients should avoid strong electromagnetic fields, such as broadcasting antennas, chainsaws, and public walkways beneath transmission power lines. Patients may pass through airport security check points without much risk to pacemaker function, but the yshould pass through the gate quickly to avoid excessive contact of the metal detector with the pacemaker.¹³ If a patient would rather not pass through the security gate, he or she can show the security office the implantable pacer device identification card and request to be patted down for security check. If a metal wand is used to screen the patient, it should be at least 6 inches from the pacemaker.¹³

Patients with pacemakers should have regular, ongoing medical monitoring with their primary physician. This can be done in the physician’s office or over the telephone. For telephone monitoring, a special transmitting device called a transtelephonic monitor is usually provided by the patient’s physician. The transtelephonic monitor allows electrical signals to be transmitted over the receiver to the physician’s office, where they are unscrambled as an ECG tracing.^{1,2,4,10,12-14} A nurse or technician analyzes the information and sends a report to the physician. All pacemakers are accompanied by identification cards. Nurses should ensure that the card is completed and should instruct the patient to carry the card at all times.

Pacemakers prolong life and improve the quality of life for patients with cardiac arrhythmia. Nurses can help by understanding pacemaker technology and providing critical information to patients about living with pacemakers.