Electrocardiography (ECG or EKG)
Electrocardiography (ECG or EKG) is a noninvasive diagnostic procedure that assesses the heart's electrical activity, providing insights into its rate, rhythm, and overall health. This essential tool is commonly used in both emergency and preventive medicine, particularly for diagnosing conditions related to chest pain. ECGs are often employed during stress tests, where heart performance is evaluated under varying levels of physical exertion, helping to identify irregularities in heart function and electrical conduction.
To perform an ECG, small metallic electrodes are placed on the skin to capture electrical signals, which are then recorded by a machine that produces a graphical representation of the heart's activity. Modern ECG technology typically uses a twelve-lead system, allowing for a comprehensive view of the heart's performance from multiple angles.
ECGs are crucial for monitoring patients with known cardiac issues, evaluating those at risk for heart disease, and conducting routine checks for athletes and certain professionals. They assist in diagnosing various conditions, including arrhythmias and heart attacks, and can influence treatment decisions based on the observed electrical patterns. Recent advancements have made ECG technology more accessible, with portable devices enabling individuals to monitor their heart health conveniently, empowering patients to take an active role in their cardiovascular care.
Electrocardiography (ECG or EKG)
- ANATOMY OR SYSTEM AFFECTED: Chest, circulatory system, heart
DEFINITION: A noninvasive procedure that provides insight into the rate, rhythm, and general health of the heart.
Indications and Procedures
Electrocardiography is a useful medical diagnostic and evaluative procedure that reveals much information about the function or malfunction of a person’s heart. ECG is a noninvasive, easy-to-use, and economical tool that is an essential part of diagnosing chest pain. It serves an important role in both and emergency medicine. ECG is also commonly used in preventive medicine to monitor heart health. For this purpose, ECG is frequently used in a format known as a stress test. Athletes often have ECG analysis performed as a part of their training and conditioning.
In a stress test, a person is studied for the regularity of rhythm, rate, and unimpeded flow of electrical conduction within the heart. ECG recordings are first made while the person is at rest, then during light exercise, and, finally, if healthy enough, during rigorous exercise. Such exercise causes the heart to work harder and allows a physician to determine whether a person has a heart that beats with a regular, repetitive rhythm and at an appropriate pace for the level of rest or exercise. The stress of exercise can also help in assessing whether the heart muscle masses contract in the proper sequence: atrial contraction followed by ventricular contraction. An irregularity of electrical conduction, poor muscle contraction, dead regions of heart tissue (from a recent or old heart attack), and other maladies can be revealed.
To obtain an electrocardiogram, small metallic contact points are taped to the patient’s skin via an electrically conductive adhesive or gel. The electric impulses travel across the skin to these contact points; from there, leads (plastic-coated wires) are attached to the recording device so that a complete circuit is made. Either a monitor screen or a strip chart recorder traces the electrical impulses. The waves are plotted in units of millivolts (on the y-axis) versus time in units of seconds (on the x-axis).
A twelve-lead ECG has replaced the original four-lead type. A twelve-lead ECG allows the physician to explore the performance of the heart from twelve different orientations or angles so that much more of the heart mass can be evaluated. Ten electrodes are placed on the body as follows: one on the right leg, which serves as the ground electrode; one on each of the other extremities; and six on the precordium, which is the area around the and on the left chest wall (over the heart). The leads are explored in different combinations.
Uses and Complications
Healthy people, including athletes or certain members of the armed services, may take stress tests to have their health and cardiovascular conditioning monitored during training. Some professionals are required to take stress tests regularly, such as commercial airline pilots and astronauts. In addition, people who have a family history of cardiovascular disease or who are concerned about their heart health for other reasons may have a stress test performed to find early warning signs and allow intervention before a crisis occurs. Finally, it should be noted that some insurance companies require stress tests of their applicants to determine insurability before issuing or rejecting a policy.
Treatment for chest pain is highly dependent on the electrical patterns seen on the ECG. Drugs may be administered or withheld depending on the shape or duration reported for the P-wave, QRS-complex, and T-wave patterns. Left-sided versus right-sided heart disease can be discerned from the traces, and (heart attack) can be distinguished from angina. Although the waves in the electrocardiogram for an infarcted or anginal heart are abnormal, the patterns become abnormal in a predictable, and therefore diagnostic, manner.
Diagnostic patterns can also be seen for arrhythmias (unusual and abnormal beating patterns), such as ectopic foci, in which some part of the heart other than the (the natural pacemaker) is abnormally in control of determining when the heart contracts, or heart block, whereby electrical conduction is interrupted.
ECG is routinely used to keep close tabs on heart patients and in the postsurgery monitoring of patients who have had open-heart or surgery. Certain kinds of neonatal or infant malformations or malfunctions may also be evaluated with ECG.
Because ECG is a superficial and technique, there are no real risks associated with having this procedure performed.
Perspective and Prospects
Electrocardiography was once a wet, messy, and awkward procedure to perform: a patient dangled one arm in a huge jar filled with a conducting salt solution and placed the left leg in another saline-filled container. Changing the leads to include other limbs required the patient to take a good amount of soaking. Although it was a clumsy procedure, the basic premise of ECG remains unchanged: the heart exhibits regular patterns of electrical activity that can be useful diagnostically.
Advances in electrocardiography have involved the use of multiple electrode systems along with computers and recorders that allow rapid and simultaneous multiple-lead input and output. In addition, modern electronic instrumentation allows continuous ECG monitoring so that patients in units, coronary care units, or emergency rooms can be assessed on a second-by-second basis when seconds count. As technology improves, ECG machines are also improved, made more portable, and work flows are simplified. Undoubtedly, modern ECG systems, coupled with thoughtful and informed interpretation by medical doctors and emergency medical technicians (EMTs), save many lives. In the 2020s, the technology behind ECGs has been made even more convenient by allowing patients to purchase portable, personal ECG systems to monitor their cardiovascular health without visiting a doctor or hospital. These devices allow patients to measure their heart rhythm and rate and keep track of additional vital health information. Patients monitoring their cardiovascular health, such as those suffering from conditions such as atrial fibrillation, are able to conveniently keep track of their own health statistics.
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