Pacemakers

Definition

A pacemaker is a surgically implanted electronic device that regulates a cardiac arrhythmia.

Pacemakers are most frequently prescribed when the heartbeat decreases under 60 beats per minute at rest (severe symptomatic bradycardia). They are also used in some cases to slow a fast heart rate over 120 beats per minute at rest (tachycardia).

Demographics

The population for pacemaker implant is not limited by age, sex, or race. Over 100,000 pacemakers are implanted per year in the United States. The occurrence is more frequent in the elderly with over 85% of implants received by those over age 65. A history of myocardial infarction (heart attack), congenital defect, or cardiac transplant also increases the likelihood of pacemaker implant.

Description

Approximately 500,000 Americans have an implantable permanent pacemaker device. A pacemaker implantation is performed under local anesthesia in a hospital by a surgeon assisted by a cardiologist. An insulated wire called a lead is inserted into an incision above the collarbone and guided through a large vein into the chambers of the heart. Depending on the configuration of the pacemaker and the clinical needs of the patient, as many as three leads may be used in a pacing system. Current pacemakers have a double, or bipolar, electrode attached to the end of each lead. The electrodes deliver an electrical charge to the heart to regulate heartbeat. They are positioned on the areas of the heart that require stimulation. The leads are then attached to the pacemaker device, which is implanted under the skin of the patient's chest.

Patients undergoing surgical pacemaker implantation usually stay in the hospital overnight. Once the procedure is complete, the patient's vital signs are monitored and a chest x ray is taken to ensure that the pacemaker and leads are properly positioned.

Modern pacemakers have sophisticated programming capabilities and are extremely compact. The smallest weigh less than 13 grams (under half an ounce) and are the size of two stacked silver dollars. The actual pacing device contains a pulse generator, circuitry programmed to monitor heart rate and deliver stimulation, and a lithium iodide battery. Battery life typically ranges from seven to 15 years, depending on the number of leads the pacemaker is configured with and how much energy the pacemaker uses. When a new battery is required, the unit can be exchanged in a simple outpatient procedure.

A temporary pacing system is sometimes recommended for patients who are experiencing irregular heartbeats as a result of a recent heart attack or other

To place a pacemaker, a lead wire is inserted into the cephalic vein of the shoulder and fed into the heart chambers (B). An electrode is implanted in the heart muscle of the lower chamber, and the device is attached (C). (

Illustration by Argosy.

)

Diagnosis/Preparation

Patients being considered for pacemaker implantation will undergo a full battery of cardiac tests, including an electrocardiogram (ECG) or an electrophysiological study or both, to fully evaluate the bradycardia or tachycardia.

The symptoms of fatigue and lightheadedness that are characteristic of bradycardia can also be caused by a number of other medical conditions, including anemia. Certain prescription medications can also slow the heart rate. A doctor should take a complete medical history and perform a full physical work-up to rule out all non-cardiac causes of bradycardia.

Patients are advised to abstain from eating six to eight hours before the surgical procedure. The patient is usually given a sedative to help him or her relax for the procedure. An intravenous (IV) line will also be inserted into a vein in the patient's arm before the procedure begins in case medication or blood products are required during the insertion.

Aftercare

After an implant without complications the patient can expect a hospital stay of one to five post-procedure days. Pacemaker patients should schedule a follow-up visit with their cardiologist approximately six weeks after the surgery. During this visit, the doctor will make any necessary adjustments to the settings of the pacemaker. Pacemakers are programmed externally with a handheld electromagnetic device. Pacemaker batteries must be checked regularly. Some pacing systems allow patients to monitor battery life through a special telephone monitoring service that can read pacemaker signals.

Patients with cardiac pacemakers should not undergo a magnetic resonance imaging (MRI) procedure. Devices that emit electromagnetic waves (including magnets) may alter pacemaker programming or functioning. A 1997 study found that cellular phones often interfere with pacemaker programming and cause irregular heart rhythm. However, advances in pacemaker design and materials have greatly reduced the risk of pacemaker interference from electromagnetic fields.

Risks

Because pacemaker implantation is an invasive surgical procedure, internal bleeding, infection, hemorrhage, and embolism are all possible complications. Infection is more common in patients with temporary pacing systems. Antibiotic therapy given as a precautionary measure can reduce the risk of pacemaker infection. If infection does occur, the entire pacing system may have to be removed.

The placing of the leads and electrodes during the implantation procedure also presents certain risks for the patient. The lead or electrode could perforate the heart or cause scarring or other damage. The electrodes can also cause involuntary stimulation of nearby skeletal muscles.

A complication known as pacemaker syndrome develops in approximately 7% of pacemaker patients with single-chamber pacing systems. The syndrome is characterized by the low blood pressure and dizziness that are symptomatic of bradycardia. It can usually be corrected by the implantation of a dual-chamber pacing system.

Normal results

Pacemakers that are properly implanted and programmed can correct a patient's arrhythmia and resolve related symptoms.

Morbidity and mortality rates

In the United States, patients experience complications in 3.3% and 3.8% of cases, with those over 65 years of age demonstrating a slightly higher complication rate of 6.1%. The most common complications include lead dislodgement, pneumothorax (collapsed lung), and cardiac perforation. The risk of death is less then 0.5% throughout the course of the hospital stay.

Resources

books

DeBakey, Michael E. and Antonio Gotto Jr. The New Living Heart. Holbrook, MA: Adams Media Corporation, 1997.

periodicals

Gregoratas, Gabriel, et al. "ACC/AHA Guidelines for Implantation of Pacemakers and Antiarrhythmia Devices." Journal of the American College of Cardiology 31 (April 1998): 1175–209.

Link, Mark S, et al. "Complications of Dual Chamber Pacemaker Implantation in the Elderly." Journal of Interventional Cardiac Electrophysiology 2 (1998): 175–179.

organizations

American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. http://www.americanheart.org .

Paula Anne Ford-Martin Allison J. Spiwak, MSBME

WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?

Pacemaker implants are performed by a cardiologist who has completed medical school and an additional internship and residency program. Additional training as an electrophysiologist may be acquired by the physician during the residency program. Specific training by the pacemaker manufacturer may also be acquired. Hospitals performing these procedures have access to cardiac catheterization facilities or operating rooms equipped with portable fluoroscopy units.

QUESTIONS TO ASK THE DOCTOR

• How many pacemaker implants has the physician performed?
• What type of pacemaker will be implanted, univentricular or biventricular, and how many of the specific procedure has the physician performed?
• How long will the expected hospital stay be?
• What precautions should be taken in the weeks following discharge from the hospital?
• What precautions will need to taken in day to day activities following pacemaker implant?
• When can normal daily, such as driving, exercise and work, activities be initiated?
• What will indicate that the pacemaker is failing and when should emergency care be sought?
• How long will the battery function and when should treatment to replace the device be sought?
• Is there special documentation I will need for air travel during security screenings?
• Will there be notification of manufacturer recalls?