Department: Heart Matters
Mr. N was golfing when he collapsed. He hadn't been on the course much the past few months because of a low energy level. He complained of weakness before the collapse, but he denied any chest pain, shortness of breath, or other symptoms to emergency medical services workers. While being monitored in the ED, Mr. N had periods of severe bradycardia, and he was admitted to the telemetry floor for placement of a pacemaker.
Setting the pace
Bradycardia is a heart rate of less than 60 beats/minute, which may or may not cause symptoms. Because Mr. N is symptomatic, he clearly has a problem, but what exactly determines heart rate?
The heart is normally paced by an electrical signal that originates in the sinoatrial (SA) node of the heart. This electrical signal is transported down through a system of other nodes and conductive fibers that stimulate each contraction. Although there are other pacing nodes, the pace or rate of beats decreases if the signal originates from any point other than the SA node.
The SA node impulse travels through the upper part of the heart to the atrioventricular, or AV, node (causing the atria to contract) and down conduction pathways to the bottom of the heart (causing the ventricles to contract). The normal heart rate is 60 to 80 beats/minute, but any stall, delay, or interruption in these pathways can cause rhythm disturbances.
Structural abnormalities, illness, cardiac drugs, aging, and scarring from cardiac events can lead to conduction difficulties, including the symptomatic bradycardia that Mr. N is experiencing. Symptomatic bradycardia is the most common reason for pacemaker placement.
A helping hand
The pacemaker is a small, battery--operated electrical device that helps maintain a normal heartbeat by delivering electrical impulses to the heart. The pacemaker detects the electrical activity that occurs in the heart and transmits it to the pacemaker generator. The pacemaker generator uses that information to initiate a tiny electrical signal to the heart to initiate a beat. This is known as pacing.
Pacing can be temporary, generally by transcutaneous or transvenous methods, or the pacemaker can be permanently placed. Pacemakers are single-chamber or dual-chamber and rate responsive. They consist of two parts: the generator and the leads. The generator is a tiny, hermetically sealed computer with a battery that sits in a titanium container. The average size of a pacemaker generator is less than 2 inches in diameter and about three-quarters of an inch thick, and it's generally placed to rest under the skin just below the collarbone. The leads are flexible, insulated electrical wires that have one end attached to the generator and another end that passes through a vein into the heart. Most pacemakers have two leads, one in the right atrium and one in the right ventricle. The battery life of modern generators is about 5 to 8 years.
To insert a pacemaker, local anesthesia is used to numb the insertion site. Then the wires from the pacemaker are threaded through the vein under the collarbone to the heart, after which the incision site is closed by sutures or adhesive skin closures (see Picturing pacemaker placement). The procedure takes about 2 hours. Most patients are admitted for a 23-hour observation following pacemaker insertion.
How does the pacemaker know when to pace? Initially, during the procedure the device is set to meet the pacing needs of the patient, and adjustments (calibrations) are done after the pacemaker is examined during follow-up appointments. Once stable, the pacemaker exams can be done over the telephone via a ring that's placed over the device.
Patient teaching tips
Patients may return to nonstrenuous activities such as slow walking as tolerated. -Instruct your patient to avoid strenuous -activity, especially activities involving the upper body, for 4 to 6 weeks. Mr. N must be sure to consult his healthcare provider before he plays golf again. Also instruct your patient to avoid excessive movement of the arm and shoulder on the same side of the body as the pacemaker for about 2 weeks to prevent dislodging the leads. Provide your patient with a sling to wear to help remind him of the limited mobility of the arm/shoulder. Driving may be -resumed in approximately 1 week.
Sutures or adhesive skin closures will be removed in about 1 week, but teach your patient that a hard ridge of tissue may remain along the incision line for some time.
Instruct your patient to avoid the following: magnetic resonance imaging scans, heat therapy, high voltage or radar machinery (such as electric arc welders, high tension wires, radar installations, or smelting furnaces), and contact with radio or television transmitters.
The pacemaker will need to be examined periodically. This painless procedure can be completed in the healthcare provider's office and via telephone. A transmitter is placed over the pacemaker, and information such as heart rhythms, battery condition, and device activity is collected.
Emphasize to your patient the importance of notifying personnel about the pacemaker on each hospital admission. Treatment plans and emergency plans may need to be modified due to the pacemaker, and pacemaker failure may cause emergent symptoms depending on the underlying disease. Your patient should also notify dentists, other healthcare providers, and airport security personnel when he travels of the presence of a pacemaker. He should keep an I.D. card with him that has information about the device.
With these precautions in place, Mr. N will be able to return to his golf game and a healthy, active life.
Learn more about it
Cardiovascular Care Made Incredibly Visual! Philadelphia, PA: Lippincott Williams & Wilkins; 2007:218–219.
Chan T, Brady W, Harrigan R. Diagnosis: pacemaker -failure to capture. Emerg Med News. 2007;29(1):11.© 2011 Lippincott Williams & Wilkins, Inc.