An electrocardiogram (ECG or EKG) is one of the simplest and fastest procedures used to evaluate the heart. Electrodes (small, plastic patches) are placed at certain locations on the chest, arms, and legs. When the electrodes are connected to an ECG machine by lead wires, the electrical activity of the heart is measured, interpreted, and printed out for the physician's information and further interpretation. An EKG is a quick, noninvasive method of assessing the heart’s function.
Other related procedures that may be used to assess the electrical activity of the heart include exercise electrocardiogram, Holter monitor, signal-averaged ECG, loop recorders and pacemaker evaluations.
Reasons for the Procedure
Some reasons for your physician to request an ECG include, but are not limited to, the following:
- to identify irregular heartbeats, or arrhythmias
- to assess how well an implanted pacemaker is functioning
- to determine the cause of chest pain
- to evaluate other signs and symptoms which may be heart-related, such as fatigue, shortness of breath, dizziness, or fainting
- to determine the status of the heart prior to procedures such as surgery and/or after treatment for conditions such as a heart attack (myocardial infarction or MI), endocarditis (inflammation or infection of one or more of the heart valves), or after procedures such as heart surgery or cardiac catheterization
- to determine the effectiveness of certain heart medications
- to obtain a baseline tracing of the heart's function during a physical examination that may be used as a comparison with future ECGs, to determine if any changes have occurred
Certain conditions such as arrhythmias (abnormal heart rhythms) may occur only intermittently, or may occur only under certain conditions, such as stress. Arrhythmias, or dysrhythmias, of this type are difficult to capture on an ECG that only runs for a few minutes. For this reason, the physician will request a specialized EKG procedure to allow a better opportunity to capture any abnormal beats or rhythms that may be causing the symptoms. These tests may include:
A Holter monitor is used to monitor the ECG tracing continuously for a period of 24 hours or longer. Some Holter monitors may record continuously but also have an event monitor feature that patients activate when symptoms begin to occur. While wearing the Holter monitor, patients are asked to keep a diary of activities and symptoms.
Event Monitoring is a procedure very similar to Holter monitoring in that patients are asked to wear a monitoring device for 24-48 hours. Unlike the Holter monitor, however, which records continuously throughout the testing period, the event monitor does not record until the patient feels symptoms and triggers the monitor to record an ECG tracing at that time. Some types of event monitors automatically record rhythms when symptoms are rare or suspected to occur during sleep. After patients experience symptoms and record them, they send the recording of the event to their physicians or to a central monitoring center by telephone. They also keep a diary of symptoms and corresponding activities experienced while wearing the monitor.
Loop Recorders, or Memory Loop Recorders
These event monitors have a feature which captures a short period of time prior to the moment the patient triggers the recording to a moment right afterwards. This feature can help the physician determine more details about the possible change in the ECG at the time the symptoms started and what was happening with the ECG just before the patient triggered the recorder.
A signal-averaged electrocardiogram is a more detailed type of ECG. During this procedure, multiple ECG tracings are obtained over a period of approximately 20 minutes in order to capture abnormal heartbeats which may occur only intermittently. A computer captures all the electrical signals from the heart and averages them to provide the physician more detail regarding how the heart's electrical conduction system is working.