|
The content on or accessible through Medpedia.com is for informational purposes only. Medpedia is not a substitute for professional advice or expert medical services from a qualified health professional.
Read more
|
Electrocardiogram
Ask a Question on This Topic
Important Resources for Electrocardiogram:
An electrocardiogram (ECG) is a simple and commonly used test that detects and records the electrical activity of the heart. It is used to detect and locate the source of heart problems. In 1901, Willem Einthoven was the first to develop a sensitive ECG, and the first to systematically analyze the readouts. He was awarded a Nobel Prize in Medicine for his methodology 23 years later.
Contents |
Other Names
An ECG is sometimes called an EKG or a 12-lead ECG (or 12-lead EKG) because the electrical activity of the heart is most often recorded from 12 different places on the body at the same time.
Description
The heart has two sides, separated by an inner wall called the septum. The right side of the heart pumps blood to the lungs to pick up oxygen. Then, oxygen-rich blood returns from the lungs to the left side of the heart, and the left side pumps it to the body. The heart has four chambers, called the left atrium, right atrium, left ventricle and right ventricle. Veins carry blood from the body to the heart, and arteries carry blood away from the heart to the rest of the body.
A healthy heart cross-section
The illustration shows a cross-section of a healthy heart and its inside structures. The blue arrow shows the direction in which oxygen-poor blood flows from the body to the lungs. The red arrow shows the direction in which oxygen-rich blood flows from the lungs to the rest of the body.
Electrical signals in the heart trigger heartbeats. These signals start at the sinoatrial node, situated on top of the heart’s right atrium. The impulses travel through the two atria and activate the atrioventricular node at the base of the left atrium. From there, the impulse travels to the base of the ventricles and then it is conducted throughout the heart muscle of the ventricles. The heart contracts as the electrical signals travel through the ventricles. During contraction, the heart pumps blood out to the rest of the body.
An ECG shows how fast the heart is beating, the heart's rhythm (regular or irregular), and where in the heart the heartbeat is being recorded. It also records the strength and timing of the electrical signals as they pass through each part of the heart.
Why an Electrocardiogram is done
An ECG is used to evaluate symptoms of heart problems. Some of these symptoms include the following:
- Chest pain.
- Heart pounding, racing, or fluttering, or the sense that the heart is beating unevenly.
- Feeling tired and weak (fatigue).
- Difficulty breathing.
- Unusual heart sounds.
In people over 40 years of age, ECGs are sometimes used in routine medical visits to screen for early heart disease that has no symptoms. The doctor is more likely to look for early heart disease if the person has a family history of heart disease in a mother, father, brother, or sister especially if the heart disease developed early in those family members' lives. Doctors also use ECGs to check how well heart treatments, such as drugs or medical devices, are working.
Types
The resting 12-lead ECG records only a few minutes of heart signals at a time, therefore, it will show a heart problem only if the problem is present during the few minutes that the test is being run. Many heart problems are present all the time, and thus this test is sufficient to detect any of these problems. However, some anomalies, such as those related to irregular heartbeats, can come and go. They may be present for only a few minutes out of the day, or while performing specific daily activities (e.g., exercising). In these situations, special types of ECGs are used to help diagnose these types of anomalies. The different ECGs that can be used in these situations are:
- Stress test
- Holter monitor
- Event monitor
Stress test
Some heart problems are easier to diagnose when the heart is working harder and beating faster than when it's at rest. During stress testing, exercise or medications are used to make the heart beat faster and work harder while conducting the ECG. Often treadmills or stationary bikes are used for exercise.
Holter monitor
Also called an ambulatory EKG, this device records the electrical signals of the heart for a full 24- or 48-hour period. The electrodes are attached to the chest and are connected by wires to a small, portable recorder that can be clipped to a belt, kept in a pocket, or hung around the neck. Daily activities are performed while wearing the monitor and any symptoms are recorded in a notebook. Both the monitor and the notebook are returned to the doctor after the designated time.
Event monitors
Similar to the Holter monitors, event monitors are portable ECGs. Event monitors can be worn for more than a month and are used to detect abnormalities of short duration and that occur infrequently. The heart's activity is only recorded after pushing a button on the device. In this way, only cardiac events are monitored and not regular heart rhythyms.
How an Electrocardiogram is Done
An ECG is painless. The most common ECG is called a resting 12-lead EKG. In this procedure, a technician first attaches 12 soft patches called electrodes to the skin of the chest, arms, and legs, these electrodes are about 2.4 cm (1 inch) in diameter. Sometimes a patch of hair where the electrode is attached needs to be shaved to help it stick. After the electrodes are placed on the skin, the patient lies still on a table for a few minutes while the electrodes detect the electrical signals of the heart. A machine then records these signals on graph paper or displays them on a screen.
The entire test takes about ten minutes. After the test, the electrodes are removed from the skin and discarded.
Benefits
Many heart problems change the electrical signature of the heart in distinct ways. ECG recordings of this electrical activity can help reveal a number of heart problems:
- Heart attacks (those occurring at the present time or those that occurred in the past)
- Lack of blood flow to the heart muscle.
- Abnormal heart rate (rapid or slow heart beats).
- Weak heart that doesn’t pump enough blood.
- Heart muscle that is too thick or parts of the heart that are too big.
- Birth defects of the heart.
- Disease in the heart valves between the different heart chambers.
An ECG also reveals whether the heartbeat starts at the right atrium (top right part of the heart) like it should. It shows how long it takes for the electrical signals to travel through the heart.
Clinical Trials
Clinical trials open for recruitment from ClinicalTrials.gov
History
The history of EKG can be pinpointed to the late 1800s when, during his posgraduate studies, Alexander Muirhead came up with the idea to attach wires to the wrist of a feverish patient as a way to measure her heartbeats. [7]
The big breakthrough came in 1911 when Willem Einthoven discovered the string galvanometer and then assigned the letters P, Q, R, S and T to the different deflections of the reading. [8] After this he went on to describe the specific reading in the electrocardiogram for different cardiovascular diseases. He won the Nobel prize in Physiology and Medicine in 1924 for his discoveries. [9]
References
- ↑ http://commons.wikimedia.org/wiki/Image:Ekg_bigeminus_strip_bionerd.jpg
- ↑ http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_all.html
- ↑ http://www.nhlbi.nih.gov/health/dci/Diseases/stress/stress_during.html
- ↑ http://www.nhlbi.nih.gov/health/dci/Diseases/holt/holt_when.html
- ↑ http://commons.wikimedia.org/wiki/Image:Precordial_Leads.jpg
- ↑ http://www.nia.nih.gov/HealthInformation/Publications/AgingHeartsandArteries/chapter05.htm
- ↑ Johansson BW. A history of the electrocardiogram. Dan Medicinhist Arbog. 2001:163-76. Abstract
- ↑ Einthoven W. Un nouveau galvanometre. Arch Neerl Sc Ex Nat 1901; 6:625
- ↑ Cooper J (1986). "Electrocardiography 100 years ago. Origins, pioneers, and contributors". N Engl J Med 315 (7): 461–4 Abstract
External links
American Heart Association: Electrocardiogram
To suggest changes to this page, you must create an account on Medpedia.
|
The content on or accessible through Medpedia.com is for informational purposes only. Medpedia is not a substitute for professional advice or expert medical services from a qualified health professional.
Read more
|