Electrocardiogram (ECG, EKG)
Electrocardiogram (ECG or EKG) is a painless process that records the heart's electrical activity. Small metal electrodes are placed on the person's wrists, ankles and chest. The electrical signals travel from the electrodes through wires to the EKG machine, which transforms the signals into patterns or waves. Different waves represent different areas of your heart through which electrical currents flow. These current cause the heart muscles to contract and relax. The P wave represents the current in the upper chambers of the heart (atria); the QRS complex represents current in the lower heart chambers
(ventricles); and the T wave represents the heart's brief "rest period" as it recharges electrically (repolarizes) between heartbeats. An Electrocardiogram (ECG or EKG, abbreviated from the German Elektrokardiogramm) is a graphic produced by an electrocardiograph, which records the electrical voltage in the heart in the form of a continuous strip graph. It is the prime tool in cardiac electrophysiology, and has a prime function in screening and diagnosis of cardiovascular diseases.
An EKG gives two major kinds of information. First, by measuring time intervals on the EKG, a doctor can determine how long the electrical wave takes to pass through the heart. Finding out how long a wave takes to travel from one part of the heart to the next shows if the electrical activity is normal or slow, fast or irregular. Second, by measuring the amount of electrical activity passing through the heart muscle, a pediatric cardiologist may be able to find out if parts of the heart are too large or are overworked. An EKG can be used to evaluate someone with chest pain, people who may be having a heart attack, and those suspected of having coronary artery disease or a cardiac arrhythmia. It also can help to diagnose an inflammation of the membrane around the heart (pericarditis), a blood clot blocking blood flow in a lung (pulmonary embolism), abnormal blood levels of potassium or calcium, or overdoses of certain medications. An EKG sometimes is used as part of a regular physical examination or as a screening test in people at high risk of heart problems, including people with high blood pressure (hypertension), high cholesterol, diabetes, a strong family history of heart problems, and people who smoke. The EKG sometimes will show the person has coronary artery disease even if there are no symptoms. During surgery, an EKG tracing helps to monitor the functioning of the person's heart.
An electrocardiogram can be performed in a doctor's office, cardiology suite or at the hospital bedside. The person is placed in a reclining position with the extremities and chest exposed. Electrodes are placed on the upper arms, lower legs and chest utilizing either straps or suction cups. Conductive gel may be applied to the skin before the electrodes are placed. During this test, you will be asked to remain still, since patient movement affects the quality. A graphic printout is obtained and forwarded to a physician for interpretation. The entire test is takes about five to 10 minutes. It requires no special preparation or aftercare.
Several sensors called electrodes will pick up the electrical activity in the heart. Your child will lie down, and technicians will put several patches (electrodes) on the chest, arms and legs. Usually the electrodes are soft and don’t cause any discomfort when they’re put on or taken off by the technician. The electrodes are connected to wires called leads, which are connected to the EKG machine. The electrical activity of the heart then is recorded on a moving strip of paper in the EKG machine. If your child is young or anxious, you or a second technician may be needed to help provide reassurance. During the EKG recording, your child must lie quietly for 10-20 seconds, because the electrocardiograph will detect any muscle or body movement.
ECG leads are attached to the body while the patient lies flat on a bed or table. Leads are attached to each extremity (4 total) and to 6 pre-defined positions on the front of the chest. A small amount of gel is applied to the skin, which allows the electrical impulses of the heart to be more easily transmitted to the ECG leads. The leads are attached by small suction cups, Velcro straps, or by small adhesive patches attached loosely to the skin. The test takes about 5 minutes and is painless. In some instances, men may require the shaving of a small amount of chest hair to obtain optimal contact between the leads and the skin.
An electrocardiogram can provide information about your heart rate and rhythm. A normal resting heart rate is 60 to 80 beats per minute. Disturbances in heart rhythm, when present on the EKG, show the electrical component of the heart is malfunctioning. If you have suffered a myocardial infarction (heart attack), the electrocardiogram will help to pinpoint the area and extent of heart muscle damage. When the pumping chamber of the heart becomes enlarged, as a result of overwork, it shows on the electrocardiogram.
The ECG is a static picture and may not reflect severe underlying heart problems at a time when the patient is not having any symptoms. The most common example of this is in a patient with a history of intermittent chest pain due to severe underlying coronary artery disease. This patient may have an entirely normal ECG at a time when he is not experiencing any symptoms. In such instances, the ECG as recorded during an exercise stress test may reflect an underlying abnormality while the ECG taken at rest may be normal.
Many abnormal patterns on an ECG may be non-specific, meaning that they may be observed with a variety of different conditions. They may even be a normal variant and not reflect any abnormality at all. These conditions can often be sorted out by a physician with a detailed examination, and occasionally other cardiac tests (e.g., echocardiogram, exercise stress test).
In some instances, the ECG may be entirely normal despite the presence of an underlying cardiac condition that normally would be reflected in the ECG. The reasons for this are largely unknown, but it is important to remember that a normal ECG does not necessarily preclude the possibility of underlying heart disease. Furthermore, a patient with heart symptoms can frequently require additional evaluation and testing.