Pacemakers are electronic devices that correct or prevent an abnormally slow or irregular heartbeat. Most pacemakers work by sensing the heartbeat and turning on when the heartbeat is too slow (called bradycardia), or occasionally when it is too fast (called tachycardia). Once the heartbeat returns to normal, the pacemaker turns off and goes back to sensing mode.
Typically, the heart beats with a regular rhythm at a rate between 60 and 100 beats per minute. If the heart's normal rate or rhythm changes, a person is said to have an arrhythmia. Arrythmias may occur at any age, but commonly begin to increase in frequency during midlife. An arrhythmia may require medical attention and treatment when it occurs repeatedly or causes symptoms such as:
Palpitations, heart beats that the person can feel
- Dizziness or lightheadedness
- Syncope (fainting)
- Dyspnea (shortness of breath)
- Chest pain.
To understand how arrhythmias are treated, it helps to know how a healthy heart beats. The four heart chambers are connected by an intricate electrical system. Each heartbeat starts in the right atrium, where the sinoatrial (sinus or SA) node, the heart's natural pacemaker, sends out an electrical signal. The signal moves through the two atria, where it stimulates the atrial muscles to contract and push blood into the ventricles. The electrical impulse then moves to the atrioventricular (AV) node, in the center of the heart, where normally it pauses for less than one-fifth of a second. From the AV node, the impulse travels through an electrical structure called the bundle of His and then into the left and right bundle branches which carry electrical impulses to the left and right ventricles, respectively, stimulating them to contract.
Normally, the atria and the ventricles contract in a coordinated manner. The atria contract first and then a fraction of a second later, the ventricles contract. Each ventricular contraction is a heartbeat.
Most pacemakers are installed to counteract disorders of impulse generation (failure of an electrical impulse to fire in the first place or fire from the wrong spot) and of impulse conduction (problems with how the electrical impulse travels through the electrical system of the heart). In impulse generation problems, the sinus node may not fire frequently enough to generate a fast enough heart beat to meet the demands of the body, for example. In disorders of impulse conduction, the electrical signal might not travel properly through the heart, slowing or even stopping its journey, also resulting in inappropriately slow heart rates.
Artificial pacemakers have been used for more than 40 years. Each year, physicians implant approximately 600,000 pacemakers worldwide. At a basic level, pacemakers consist of an electronic device called a pulse generator and wires called leads that attach to the heart. The leads transmit electrical signals from the generator, and stimulate the heart's chambers to contract. Pacemakers also sense the electrical activity of the heart. They stimulate the heartbeat if it is too slow, and go on “stand-by mode” if the heart is beating fast enough.
When Is It Indicated?
People usually need a pacemaker when the heart beats too slowly. Rarely, patients with fast heart beats may benefit from pacemakers, if their arrhythmias are triggered by heart rates that are too slow. Indications for a pacemaker include:
- Heart block which occurs when electrical stimuli sent by the SA or AV node do not reach their targeted muscle cells
- Bradycardia, an inappropriately slow heartbeat. This has many causes.
Before implanting a pacemaker.
Prior to pacemaker implantation, the physician may order an electrocardiogram(ECG) and an echocardiogram. Electrocardiography uses electrodes to monitor the heart's electrical function, and echocardiography uses high-frequency sound waves called ultrasound to create a moving picture of the beating heart and locate any structural abnormalities. Additionally, the physician will ask the person for a list of medications he or she is taking, perform blood tests, and consider the person's vascular health.
On the day of the procedure, the person needs to do little preparation other than communicate how he or she is feeling, make sure the physician knows about all medications taken within the past month, and in most cases avoid eating and drinking for 8 to 12 hours prior to the surgery, which will reduce the risk of complications from sedation or anesthesia.
Who Is Eligible?
Because pacemaker implantation usually is a relatively straightforward procedure, there are few people for whom receiving a pacemaker would be contraindicated. Currently, more than 3 million people in the world have pacemakers.
Pacemakers can be permanent or temporary. Patients likely to receive a temporary pacemaker are those who have a transient problem with slow heart rates because of one or more of the following:
- Heart medications that can interfere with the electrical system
- Heart attack (not all heart attacks cause a slow heart rate)
- Upcoming surgery, if the person has pre-existing electrical problems
Patients likely to receive a permanent pacemaker include those who have:
What to expect.
Implantation procedures for temporary and permanent pacemakers differ and are discussed separately below.
Temporary pacemaker. A temporary pacemaker is generally an external device that is put in place while the person is in the hospital for a related heart condition (e.g., following a heart attack). This procedure, which involves threading a pacing wire through a vein, into the heart, can take place at the person's bedside or in a specialized cardiac catheterization laboratory.
First, the physician will administer a sedative if the person is anxious about the procedure, and a local anesthetic to prevent pain at the insertion site (usually in the neck or groin area). Next, a small wire is guided into the vein and a sheath (a small hollow tube) is placed into the vein over the wire, and the wire is withdrawn. The sheath acts as a one way valve, allowing a pacing catheter to be place through it, but preventing blood from flowing back out. The physician then guides the pacing catheter to the right ventricle using fluoroscopy (moving X-ray images projected on a screen). Metal tips on the catheter deliver electrical signals to pace the heartbeat. A battery-powered external device connected to the leads provides electrical impulses, which travel to the electrodes in the heart and cause the heart to beat. Because there are no nerves inside the blood vessels, the person will not feel the catheter as it moves toward the heart, and the procedure is generally painless.
Permanent pacemaker implantation. Permanent pacemaker insertion is considered minor surgery, and can be done on an inpatient or an outpatient basis. The procedure may be performed in an electrophysiology laboratory, operating room, or outpatient surgical facility. The person stays awake during the procedure, which takes approximately 1 hour. A light sedative is used to make the patient comfortable.
In most cases, the pacemaker is placed beneath the skin on the front of the chest under the clavicle (collarbone). The physician will apply a local anesthetic and clean and shave the incision site. Next, he or she creates a small pocket in the chest wall just below the clavicle and places the pacemaker into the pocket. The pacemaker leads are then passed through a vein in the upper chest and directed to the right atrium or right ventricle, or both chambers, using fluoroscopy for guidance. Small screws attach the leads to the inner surface of the heart chamber or chambers. Following insertion, the skin is closed with sutures or staples.
After a pacemaker is implanted
Recovery from either temporary or permanent pacemaker implantation is relatively uncomplicated. Patients with a temporary pacemaker will be advised not to twist or otherwise manipulate the pacemaker while it is in place. The temporary pacemaker will be removed prior to discharge from the hospital.
Most patients who receive a permanent pacemaker are discharged to go home on the day of implantation. Some people with a permanent pacemaker may stay in the hospital for 1 or 2 days so that the physician can confirm that their condition is stable and the pacemaker in functioning properly. The physician may order an X-ray, ECG, or echocardiogram to make sure the pacemaker and leads are in the proper location and working correctly. Ten to 14 days after surgery, the sutures or staples will be removed.
You will receive specific instructions from your physician in regards to the care of your pacemaker. In general, in the weeks and months after the procedure, people should care for the pacemaker in the following ways:
- In the first few days, limit heavy lifting, exercise, and other strenuous or stressful activity to reduce stress on the healing incision site;
- For several months, avoid activities requiring movement of arms above the head (e.g., golf), to allow the pacemaker leads to attach well to the inside of the heart. Patients should permanently avoid contact sports, which could dislodge the pacemaker; and
- Measure their resting pulse rate for 1 full minute each day, and contact the physician if their pulse is 5 or more beats below the programmed rate, or more than 100 beats per minute.
Some permanent adjustments that people will need to consider include:
- Carrying a card identifying that the person has a pacemaker and stating the particular model, for emergency medical and airport security personnel;
- Informing physicians and dentists about the pacemaker before having any tests or procedures; and
- Exercising caution around certain electronic or magnetic devices such as magnetic resonance imaging (MRI) machines. Some amusement park rides, industrial magnets, and high-powered stereo equipment (if very close to the person's chest) can interfere with pacemaker's programming. Cell phones, computers, and microwave ovens are not considered to pose a serious risk to pacemaker function. Digital cell phones should not be placed in chest pockets directly over the pacemaker.
Once the pacemaker is fully adjusted and the incision site has healed, the person should be able to carry out all the functions of normal daily life, such as bathing, exercising moderately, having sexual intercourse, and driving. The pacemaker automatically adapts to various circulation and heartbeat needs.
Generally, the person's physician will want to check the pacemaker's programming and battery function every 6 to 12 months. A technology known as transtelephonic monitoring can allow the physician to check on the device's programming and battery power via a regular telephone. Physician visits may include a medical history update, blood pressure check, x ray, ECG, and a stress test.
The batteries of most pacemakers are made of lithium iodide and can last from 5 to 15 years. Battery life depends on several factors, including the number of leads and how much power the pacemaker uses. Because pacemaker batteries are designed to lose power gradually, sudden failure is unlikely, and plenty of notice is available before the pacemaker runs out of power. If the battery is failing, physicians will implant a new generator (the leads/wires will not need to be changed – they will simply be reattached to the new generator). If the person senses that his or her heartbeat is slowing down, however, he or she should contact their physician because this may indicate a serious problem.
Possible Complications
The vast majority of pacemaker implantations go smoothly. A rare complication associated with insertion is severe bruising or bleeding at the insertion site. Extremely rare complications include:
- Formation of blood clots
- Tearing of a blood vessel
- Puncturing of the lung or heart muscle
- Introduction of air into the space between the lung and chest wall, which could collapse a lung.
Complications that affect pacemaker function after insertion occur in only 1 to 2 percent of cases, and include:
- A lead wire dislodging from the heart (this will require re-positioning of the lead)
- Pacemaker malfunction (this is usually solved by re-programming the pacemaker)
- Infection of the pocket into which the pacemaker was placed (this will require removal of all pacemaker components)
