The formal procedure for obtaining an ECG is given in Chapter 13, Electrocardiogram. Every ECG should be approached in a systematic, stepwise way. Many automated ECG machines can give a preliminary interpretation of a tracing; however, all automated interpretations require analysis and sign-off by a physician. Determine each of the following: Show
Figure 19–1. Examples of 10-mm standardization mark and time marks and standard ECG paper running at 25 mm/s. Figure 19–2. Diagram of the ECG complexes, intervals, and segments. The U wave is normally not well seen. EquipmentBipolar Leads
Precordial Leads:V1 to V6 across the chest (see Figure 13–9).
ECG Paper:With the ECG machine set at 25 mm/s, each small box represents 0.04 s, and each large box 0.2 s (see ... ECG; EKG An electrocardiogram (ECG) is a test that records the electrical activity of the heart. If your
heart has been beating too fast, or you've been having chest pain, both you and your doctor will want to find out what's causing the problem so you can get it treated. One way to diagnose heart problems is with a test of the heart's electrical activity, called an electrocardiogram or ECG, or EKG for short. Your heart is controlled by an electrical system, much like the electricity that powers the lights and appliances in your home. Electrical signals make your heart contract so that it can pump
blood out to your body. Heart disease, abnormal heart rhythms, and other heart problems can affect those signals. Using an ECG, your doctor can identify problems in your heart's electrical system and diagnose heart disease. So, how is an ECG done? First you'll lie down on a table. You'll have to lie very still while the test is done. Small patches, called electrodes, will be attached to several places on your arms, legs, and chest. The patches won't hurt, but some of the hair in those areas may
be shaved so the patches will stick to your skin. The patches are then attached to a machine. You'll notice that when the machine is turned on, it produces wavy lines on a piece of paper. Those lines represent the electrical signals coming from your heart. If the test is normal, it should show that your heart is beating at an even rate of 60 to 100 beats per minute. Many different heart conditions can show up on an ECG, including a fast, slow, or abnormal heart rhythm, a heart defect, coronary
artery disease, heart valve disease, or an enlarged heart. An abnormal ECG may also be a sign that you've had a heart attack in the past, or that you're at risk for one in the near future. If you're healthy and you don't have any family or personal history of heart disease, you don't need to have an ECG on a regular basis. But if you are having heart problems, your doctor may recommend getting this test. An ECG is pretty accurate at diagnosing many types of heart disease, although it doesn't
always pick up every heart problem. You may have a perfectly normal ECG, yet still have a heart condition. If your test is normal but your doctor suspects that you have a heart problem, he may recommend that you have another ECG, or a different type of test to find out for sure. The electrocardiogram (ECG) is used extensively in the diagnosis of heart disease, from congenital heart disease in infants to myocardial infarction and myocarditis in adults. Several different types of electrocardiogram exist. This picture shows an ECG (electrocardiogram, EKG) of a person with an abnormal rhythm (arrhythmia) called an atrioventricular (AV) block. P waves show that the top of the heart received electrical activity. Each P wave is usually followed
by the tall (QRS) waves. QRS waves reflect the electrical activity that causes the heart to contract. When a P wave is present and not followed by a QRS wave (and heart contraction), there is an atrioventricular block, and a very slow pulse (bradycardia). Routine lab tests are recommended before beginning treatment of high blood pressure to determine organ or tissue damage or other risk factors. These lab tests include urinalysis, blood cell count, blood chemistry (potassium, sodium, creatinine, fasting glucose, total cholesterol and HDL cholesterol), and an ECG (electrocardiogram).
Additional tests may be recommended based on your condition. An electrocardiogram is a test that measures the electrical activity of the heart. This
includes the rate and regularity of beats as well as the size and position of the chambers, any damage to the heart, and effects of drugs or devices to regulate the heart. An ECG is very useful in determining whether a person has heart disease. During an ECG electrodes are affixed to each arm and leg and to the chest. Action potentials generated by heart cells produce weak electrical currents that spread throughout the body. These currents can be detected at the surface of the body and amplified using an instrument known as an electrocardiograph. The graphic recording produced by an electrocardiograph of the heart electric activity is
called an electrocardiogram, or ECG. If your heart has been beating too fast, or you've been having chest pain, both you and your doctor will want to find out what's causing the problem so you can get it
treated. One way to diagnose heart problems is with a test of the heart's electrical activity, called an electrocardiogram or ECG, or EKG for short. Your heart is controlled by an electrical system, much like the electricity that powers the lights and appliances in your home. Electrical signals make your heart contract so that it can pump blood out to your body. Heart disease, abnormal heart rhythms, and other heart problems can affect those signals. Using an ECG, your doctor can identify
problems in your heart's electrical system and diagnose heart disease. So, how is an ECG done? First you'll lie down on a table. You'll have to lie very still while the test is done. Small patches, called electrodes, will be attached to several places on your arms, legs, and chest. The patches won't hurt, but some of the hair in those areas may be shaved so the patches will stick to your skin. The patches are then attached to a machine. You'll notice that when the machine is turned on, it
produces wavy lines on a piece of paper. Those lines represent the electrical signals coming from your heart. If the test is normal, it should show that your heart is beating at an even rate of 60 to 100 beats per minute. Many different heart conditions can show up on an ECG, including a fast, slow, or abnormal heart rhythm, a heart defect, coronary artery disease, heart valve disease, or an enlarged heart. An abnormal ECG may also be a sign that you've had a heart attack in the past, or that
you're at risk for one in the near future. If you're healthy and you don't have any family or personal history of heart disease, you don't need to have an ECG on a regular basis. But if you are having heart problems, your doctor may recommend getting this test. An ECG is pretty accurate at diagnosing many types of heart disease, although it doesn't always pick up every heart problem. You may have a perfectly normal ECG, yet still have a heart condition. If your test is normal but your doctor
suspects that you have a heart problem, he may recommend that you have another ECG, or a different type of test to find out for sure. You will be asked to lie down. The health care provider will clean several areas on your arms, legs, and chest, and then will attach small patches called electrodes to those areas. It may be necessary to shave or clip some hair so the patches
stick to the skin. The number of patches used may vary. The patches are connected by wires to a machine that turns the heart's electrical signals into wavy lines, which are often printed on paper. The doctor reviews the test results. You will need to remain still during the procedure. The provider may also ask you to hold your breath for a few seconds as the test is being done. It is important to be relaxed and warm during an ECG recording because any movement, including
shivering, can alter the results. Sometimes this test is done while you are exercising or under light stress to look for changes in the heart. This type of ECG is often called a stress test. How to Prepare for the TestMake sure your provider knows about all the medicines you are taking. Some drugs can interfere with test results. Do not exercise or drink cold water immediately before an ECG because these actions may cause false results. How the Test will FeelAn ECG is painless. No electricity is sent through the body. The electrodes may feel cold when first applied. In rare cases, some people may develop a rash or irritation where the patches were placed. Why the Test is PerformedAn ECG is used to measure:
An ECG is often the first test done to determine whether a person has heart disease. Your provider may order this test if:
Normal ResultsNormal test results most often include:
What Abnormal Results MeanAbnormal ECG results may be a sign of:
Some heart problems that can lead to changes on an ECG test include:
RisksConsiderationsThe accuracy of the ECG depends on the condition being tested. A heart problem may not always show up on the ECG. Some heart conditions never produce any specific ECG changes. ReferencesBrady WJ, Harrigan RA, Chan TC. Basic electrocardiographic techniques. In: Roberts JR, Custalow CB, Thomsen TW, eds. Roberts and Hedges' Clinical Procedures in Emergency Medicine and Acute Care. 7th ed. Philadelphia, PA: Elsevier; 2019:chap 14. Ganz L, Link MS. Electrocardiography. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 48. Mirvis DM, Goldberger AL. Electrocardiography. In: Libby P, Bonow RO, Mann DL, Tomaselli GF, Bhatt DL, Solomon SD, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 12th ed. Philadelphia, PA: Elsevier; 2022:chap 14. Version InfoLast reviewed on: 5/8/2022 Reviewed by: Michael A. Chen, MD, PhD, Associate Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. |