An Electrocardiogram (ECG) is a test that measures the electrical activity of the heartbeat. With each heart beat, an electrical impulse (or “wave”) travels through the heart. This wave then causes the muscle to squeeze and pump blood from the heart.
Electrocardiography also known as EKG or ECG is a procedure which records the electrical activity of the heart, as well as valuable information about the structure of the heart and it’s function. The heart is made up of electrical “hot spots ” beginning with the SInus Node ( SA NODE), located within the Right Atrium ( one of the chambers of the heart). This initiates a wave of electrical signals which are conducted through special ions to the Atrioventricular Node ( AV NODE) located at the junction of the atria and ventricular walls.
The same signal is transferred by the AV node to the right and left branches of the conduction system in the ventricular walls after passing a ” junction box” the Bundle of His. Through this branch networks, the electrical signals are rapidly transferred to the electrical fibers ” Purkinje Fibres” in the ventricles causing the heart walls to contract and pump blood to the appropriate parts of the body.
The series of electrical activities, the pattern and pathway of its transfer from the SA Node to the rest of the heart can be detected by electrodes placed on the skin of the body, and can be recorded in a graphical form on a paper using the EKG machine. The SA node is called the heart’s Pace Maker since it will determine the speed of heart contraction depending on how much ‘current’ it sends into the system.
The ECG or EKG, will give information on the heart rate, rhythm, hypertrophy or changes in the blood flow through various segments of the heart.
Some common findings on the EKG may include Tachycardia ( Atrial or Ventricular) , Bradycardia, abnormal rhythms ( arrhythmias), heart blocks ( primary, secondary or tertiary heart block), distinction of Weckenbach and Mobitz types of Heart block, Bundle Branch Block, Axis deviations , atrial or Ventricular Hypertrophy, loss of blood supply and even tissue death(infarction) due to diseases of the coronary Arteries.
Who should come for EKG ?
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What are the preparations ?
No special preparations may be necessary. You may be required to dress with a comfortable wear, that can be easily removed. Do not drink alcohol or cold water immediately before an ECG as this may interfere with the cardiac signals.
What happens during an ECG ?
The standard, resting ECG takes a few minutes. You will be asked to undress to the waist and lie down on a bed or couch. A number of sticky patches called electrodes will be stuck onto your arms, legs and chest. If you have a lot of hair on your chest, some small patches may need to be shaved to allow the electrodes to make contact with your skin.
The electrodes are attached to a recording machine by wires. When your heart beats, it produces electrical signals which are picked up by the electrodes and transmitted to the recording machine. The machine then prints a record of your heartbeat onto a paper strip. You should lie still when the recording is being taken as moving can affect the reading.
For an exercise ECG, electrodes from the recording machine are connected to you with wires in the same way as a standard ECG. Your heart rate and blood pressure will also be recorded. You will then be asked to exercise, either by walking on a treadmill or cycling on a stationary exercise bike. If you aren’t able to exercise, sometimes a drug called adenosine can be used to stimulate the effect of exercise.
The exercise will be gentle to start with and gradually becomes more strenuous, for example, by increasing the speed or the slope of the treadmill. The doctor or technician will monitor your ECG along with your blood pressure and heart rate, every few minutes while you’re exercising.
The test will last between a few minutes and 15 minutes. It will be stopped when the doctor or technician has the readings he or she needs. The test may also be stopped if your blood pressure becomes too high, if you have chest pains or if you become short of breath. You can ask for the test to be stopped if you feel unwell.
Once your ECG and blood pressure have returned to normal, you will be able to go home.
For this test, you will be asked to wear a small portable recorder, attached to a belt around your waist. Wires from the recorder are connected to three or four small sticky patches (electrodes) on your chest.
You will usually have the recorder fitted at a hospital. You can go about your normal activities for the day, while keeping a diary of everything that you do and noting when you feel symptoms. You shouldn’t have a bath or shower with the recorder on. At the end of the 24 hours, you can remove the electrodes and recorder and return it to the hospital.
Cardiac event recorders
A portable event recorder is a small electrical device that you use when you have symptoms. When you have symptoms, such as palpitations, you place the device on your chest and switch it on to record your ECG. With most portable event recorders, you will be able to send the results of the recording to the hospital by holding the device to a phone. The doctor or technicians at the hospital can then analyse your results and tell what to do next.
An implantable loop recorder (ILR) is a small, slim device that is inserted just under the skin on the front of your chest. This is done using a local anaesthetic. It continuously monitors your heartbeat and records any unusual heartbeats. You can also start a recording if you notice any symptoms.
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