Almost everyone knows what a basic EKG tracing looks like. But what does it mean?
The first little upward notch of the EKG tracing is called the "P wave." The P wave indicates that the atria (the 2 upper chambers of the heart) are contracting to pump out blood.
The next part of the tracing is a short downward section connected to a tall upward section. This next part is called the "QRS complex." This part indicates that the ventricles (the 2 lower chambers of the heart) are contracting to pump out blood.
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The next short upward segment is called the "ST segment." The ST segment indicates the amount of time from the end of the contraction of the ventricles to the beginning of the rest period before the ventricles begin to contract for the next beat.
The next short upward segment is called the "ST segment." The ST segment indicates the amount of time from the end of the contraction of the ventricles to the beginning of the rest period before the ventricles begin to contract for the next beat.
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The next upward curve is called the "T wave." The T wave indicates the resting period of the ventricles.
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The next upward curve is called the "T wave." The T wave indicates the resting period of the ventricles.
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When your physician studies your EKG, he/she looks at the size and length of each part of the EKG. Variations in size and length of the different parts of the tracing may be significant. The tracing for each lead of a 12-lead EKG will look different, but will have the same basic components as described above. Each lead of the 12-lead is "looking" at a specific part of the heart, so variations in a lead may indicate a problem with the part of the heart associated with the lead.
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Why is an EKG done?
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Many conditions can cause changes to the EKG. Because the EKG is a fast, simple, painless and relatively inexpensive test, it may be used as a part of an initial examination to help the physician narrow the scope of the diagnostic process. EKG's are also done with routine physical examinations so that comparisons can be made with previous EKG's to determine if a hidden or undetected condition might be causing changes in the EKG. Some conditions which may cause changes in the EKG pattern may include, but are not limited to, the following:
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ischemia - decreased flow of oxygenated blood to an organ due to obstruction in an artery.
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ischemia - decreased flow of oxygenated blood to an organ due to obstruction in an artery.
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heart attack - also called myocardial infarction; damage to the heart muscle due to insufficient blood supply.
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conduction disorders - a dysfunction in the heart's electrical conduction system, which can make the heartbeat too fast, too slow, or at an uneven rate.
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electrolyte disturbances - an imbalance in the level of electrolytes, or chemicals, in the blood, such as potassium, magnesium, or calcium.
pericarditis - an inflammation of the sac (thin covering) that surrounds the heart.
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pericarditis - an inflammation of the sac (thin covering) that surrounds the heart.
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valvular heart disease - one or more of the heart's four valves becomes defective, or may be congenitally malformed.
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enlarged heart - a condition of the heart in which it is abnormally larger than normal; can be caused by various factors, such as valve disorders, high blood pressure, congestive heart failure, conduction disturbances, etc.
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enlarged heart - a condition of the heart in which it is abnormally larger than normal; can be caused by various factors, such as valve disorders, high blood pressure, congestive heart failure, conduction disturbances, etc.
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chest trauma - blunt trauma to the chest, such as a motorist hitting the steering wheel in an automobile accident.
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NOTE: This list is presented as an example. It is not intended to be a comprehensive list of all conditions which may cause changes in the EKG pattern.
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An EKG may also be done for the following reasons:
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to obtain a baseline tracing of the heart's function (during a physical examination). This baseline tracing may be used later as a comparison with future EKG's, to see if any changes have occurred.
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as part of a work-up prior to a procedure such as surgery to make sure a heart condition does not exist that might cause complications during or after the procedure
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to check the function of an implanted pacemaker
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to check the effectiveness of certain heart medications
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to check the heart's status after an MI, or after a heart-related procedure such as a cardiac catheterization, heart surgery, electrophysiological studies, etc.
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How is an EKG done?
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An EKG is one of the simplest and fastest procedures used to evaluate the heart. An EKG technician, nurse, or physician will place 12 separate electrodes (small plastic patches) at specific locations on your chest, arms, and legs. Eight of the electrodes will be placed on your chest, and one electrode will be placed on each arm and leg. The electrodes may be self-sticking, or a gel may be applied to make the electrodes adhere to the skin. You will be lying down on a stretcher or bed, and the leads (wires) will be connected to the electrodes on your skin. You will need to lie very still and not talk during the EKG procedure, as movement or talking may interfere with the tracing. The technician, nurse, or physician will start the tracing, which will take just a few minutes. You will not feel anything during the tracing. Once a clear tracing has been obtained, the leads and electrodes will be removed, and you will be free to continue on with your usual activities, unless directed otherwise by your physician. An EKG can indicate the presence of arrhythmias (an abnormal rhythm of the heart), damage to the heart caused by ischemia (lack of oxygen to the heart muscle) or myocardial infarction (MI, or heart attack), a problem with one or more of the heart valves, or other types of heart conditions.
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