Cardiac Event Monitor

Definition
Purpose
Demographics
Description
Results Obtained with Cardiac Event Monitors
Risks Associated with Cardiac Event Monitors

Definition

A cardiac event monitor is an electronic device that attaches to the body and records the rhythm of the heart while the patient is experiencing pathological symptoms. The cardiac event monitor allows recording of the heart without the inconvenience of staying in the hospital or undergoing invasive procedures.

Purpose

Patients who have symptoms of heart disease such as angina (pain from a lack of oxygen flow to the heart) or arrhythmias (irregular heartbeats) use the cardiac event monitor to record the rhythm of their heart while they are experiencing the symptoms. The cardiac event monitor was designed to record pathological events in real time, allowing for continuous heart monitoring over long periods of time. The heart is thus effectively monitored without necessity for invasive procedures or staying in the hospital. The longer the cardiac event monitor is worn by the patient, the greater the chances of catching and recording the abnormal heart rhythm of a spontaneous cardiac event. Cardiac event monitors were designed as a useful tool for patients who experience symptoms that do not occur regularly, or involve fainting, and so are difficult to analyze.

Demographics

Cardiac event monitors are used to aid in the diagnosis of heart conditions that cause irregular rhythms. They are designed for a demographic of patients that do not experience symptoms on a predictable, daily basis. Cardiac event monitors can be used for patients with abnormal heart rhythms regardless of age, race, or gender.

Description

Cardiac event monitors allow the recording of heart rhythms over long periods of time. When used properly, the monitor is able to record information about heart rhythms that assists cardiologists in diagnosing different types of heart disease. There are multiple types and designs of cardiac event monitors. Each type offers unique features.

Heart Rhythm

The heart is a contracting muscle that pumps blood to the body tissues. Oxygenated blood leaves the heart and supplies tissues with the oxygen necessary for life. Deoxygenated blood carrying carbon dioxide waste travels from the tissues back to the heart. The heart sends the deoxygenated blood carrying carbon dioxide to the lungs to be oxygenated. The oxygenated blood from the lungs returns to the heart and the cycle begins again. During this cycle of pumping blood, valves in the heart create the sound of the heartbeat as they close.

The heart rhythm should be a regular pattern of heartbeats occurring at a regular rate that is considered normal. Many types of disease may cause an irregularity in this pattern. A cardiac arrhythmia is an irregular rhythm of heartbeats that does not allow the heart to pump blood properly. Cardiac arrhythmias may cause symptoms of palpitations (pounding heart), syncope (fainting), chest pain, dizziness, lightheadedness, shortness of breath, weakness, or fatigue. When a cardiac arrhythmia does not occur regularly and so is difficult to diagnose with an electrocardiogram (ECG) reading in a hospital setting, cardiac event monitors may be utilized to help elucidate the relationship between a patient’s symptoms and the heart rhythms recorded. Cardiac event monitors may be used on patients with different types of heart conditions, including arrhythmias, myocardial infarctions (heart attacks), stroke, or during recovery from coronary artery bypass graft surgery (CABG).

Holter Cardiac Event Monitors

A Holter monitor is a general type of cardiac monitor which records heart rhythm continuously for 24 to 48 hours. Holter monitors are useful when a patient experiences symptoms on a daily basis. Holter monitors record each heartbeat, using electrodes attached to the chest. Patients using Holter monitors go through their normal daily activities (except bathing) and keep a diary of how they feel physically during the monitoring time period. When the monitoring time period is over, the Holter monitor and the accompanying diary are turned in to the diagnostic center for evaluation of the recorded results. While Holter monitors are effective, patients whose symptoms occur less frequently require the cardiac event monitor.

Looping Memory Cardiac Event Monitors

Cardiac event monitors are small black boxes attached to several wires with electrodes. The cardiac event monitor is monitoring heart rhythm as the patient goes through their daily activities. Cardiac event monitors do not record heart rhythm for more than a few minutes at a time in a cycling stream of memory. When the patient experiences symptoms it is known as a cardiac event. The patient immediately presses a button on the event monitor that records the activity of the heart while the symptom is occurring. Many cardiac events are fleeting experiences and it may take the patient a moment to press the event button, therefore, cardiac event monitors have been designed with a continuous memory “loop” that allows the recording to backtrack about 30 seconds to a minute before the event button was pressed, and obtain a complete picture of the cardiac event. If the event button is not pressed, no permanent record will be kept of the event within the basic monitor design. Some types of cardiac event monitors have been preset to record cardiac events if the heart goes into an arrhythmia and circumvent the need for the event button; however, these monitors may be less specific in the data they gather.

Cardiac event monitors are often used for 30 days. For this reason, cardiac events need to be transmitted to the diagnostic center frequently during the monitoring time frame, rather than at the end of the monitoring period. Cardiac event monitors can have their data transmitted via a telephone line to a computer system that turns the transmitted data into an ECG reading. Essentially, the cardiac event monitor provides the ability to obtain an ECG of an irregularly occurring symptom that would likely otherwise be missed in an office visit. Since transmission of data is done approximately every other time a symptom is experienced, the cardiologist is able to keep track of the patient’s condition in real time over the duration of the cardiac event monitoring. Event monitors notify physicians in a timely manner if intervention is needed for a serious cardiac arrhythmia that might have otherwise have been missed.

Implantable Cardiac Event Monitors

Implantable cardiac event monitors were designed for use in patients with unexplained syncope that may have a heart-related cause. The implantable monitors are surgically placed just under the skin of the chest within a one-inch incision. The implantation procedure involves only local anesthesia. Implantable cardiac event monitors are set to specific heart rhythm limits in order to obtain a record of heart events during syncope episodes. The implantable design that does not require pressing an event button is critical to record events that involve a patient losing

QUESTIONS TO ASK YOUR DOCTOR

• Why do I need a cardiac event monitor?
• Which type of cardiac event monitor will I be using?
• What are the advantages and disadvantages of this type of monitor over other types?
• How should I prepare for the cardiac event monitor?
• Are there any restrictions on my daily activity with the cardiac event monitor?
• How do I use the cardiac event monitor?
• How long will I use the cardiac event monitor?
• When can I expect to go over the results of my cardiac event monitor?
• Could any of my prescription or nonprescription medications, nutritional, or herbal supplements be causing my symptoms or affect the results?

consciousness. After a period of time, the monitor is removed and its data is analyzed by a diagnostic center.

Mobile Cardiovascular Telemetry

Cardiac event monitors have been designed for use with a wireless cell phone system that transmits data from the monitor without the need of calling in a transmission to a diagnostic center. These devices act as both a monitor and an alarm system for patients with potentially life threatening cardiac arrhythmias. The remote diagnostic center and patient’s physician automatically receive daily reports of the patient’s heart activity. In addition to daily reports, any urgent, life threatening data gathered by the device is immediately transmitted. In this way, the remote diagnostic center and physician are notified relatively quickly in urgent circumstances and intervention can be made in a timely manner.

Results Obtained with Cardiac Event Monitors

The recordings obtained by cardiac event monitors are sent to cardiac event monitor diagnostic centers and converted into ECG readings. Trained health care professionals interpret the ECG readings. Cardiologists are heart doctors that specialize in diagnosing heart disease, and use ECGs as tools to assist in a patient’s diagnosis. Cardiac event monitors alone

KEY TERMS

Angina— Condition causing chest discomfort or pain due to a decreased oxygen supply to the heart.

Arrhythmia— An irregular pattern of heartbeats that affects how well the heart pumps blood and can be life threatening.

Coronary Artery Bypass Graft Surgery (CABG)— A surgical procedure where arteries or veins from elsewhere in the patient’s body grafted into the arteries of the heart as a way to bypass damaged or narrowed heart blood vessels. Heart blood vessels may have been damaged or narrowed from fat deposition and need to be bypassed to increase the blood supply and oxygen delivered to the heart.

Electrocardiogram (ECG)— A medical tool used to monitor the electrical impulses released by the beating heart. The results are drawn out in graphical fashion to visualize the function of the heart.

Palpitations— Forcible pulsation or pounding of the heart that is perceptible to the patient.

Syncope— A fainting episode.

cannot diagnose heart conditions, but only display the heart rhythm a patient is experiencing at the time of symptom onset. Cardiologists may use ECGs to help narrow down the diagnosis whether or not the condition is caused by an arrhythmia.

Risks Associated with Cardiac Event Monitors

Cardiac event monitors are useful tools, but may not be sensitive enough to catch every cardiac event or specific enough to detail it well. Different designs have different levels of sensitivity in picking up events and give different levels of detail about the events they record. Even with designs in which event recording is automatic, some data may be missed.

Resources

BOOKS

Andreoli, Thomas E., Charles C. J. Carpenter, Robert Griggs, and Joseph Loscalzo Cecil Essentials of Medicine, 6th ed. Philadelphia: Saunders, 2004.

Costanzo, Linda S. Physiology, 3rd ed. Philadelphia: Saunders, 2006.

OTHER

Chang, Bernard S. Steven C. Schachter, and Donald L. Schomer. “Event Monitoring,” in Atlas of Ambulatory EEG. 2005. http://books.google.com/books?id=MOcDuNt9kqwC&pg=PA20&dq=cardiac+event+monitoring&sig=zkviXpNDvhViSqYH5La-ViTBStiE (April 9, 2008).

Committee on Congenital Cardiac Defects of the Council on Cardiovascular Disease in the Young. “What are Holter, Event, and Transtelephonic Monitors?” American Heart Association. http://www.americanheart.org/presenter.jhtml?identifier=3005149 (April 9, 2008).

Khandpur, Raghbir Singh. Biomedical Instrumentation: Technology and Applications. New York: McGraw-Hill Professional, 2004. http://books.google.com/books?id=BMNLEoz8S0MC&pg=PA257&dq=cardiac+event+monitoring&sig=NCQA7Q4rsC4nuhGoGO-VDk2JvAI (April 9, 2008).

Zeevi, Bejamin. “Telecardiology,” in Telemedicine and Teledermatology, edited by Gunter Burg. Basel, Switzerland: Karger, 2002. http://books.google.com/books?id=F2FyQ1DgptgC&pg=PA118&dq=cardiac+event+monitoring&sig=jDUtACUMedc0-0XftNuVMQydKwI (April 9, 2008).

Maria Basile, Ph.D.

Cardiac exercise stress testing seeStress test

Cardiac mapping seeElectrophysiology study of the heart