What is Electrocardiogram and How Does It Work?


People who have recently lost a loved one from a heart attack know how important it is to capture the right data about a person’s overall health status. The ability to access this information promptly is vital as it will give the patient and their family enough time to prepare for the proper measures to take in order to prevent any aggravation of the heart’s condition and/or to avert sudden death caused by heart malfunction. In fact, a recent study conducted by AHA shows that one woman is killed by stroke and heart disease for about every 80 seconds.


With the advent of medical equipment and technology, we can’t help but thank the benefits it brought to our medical industry in saving many lives and helping other patients when recuperating from terminal diseases. One particular example of this is the Electrocardiogram.


What is Electrocardiogram?

Electrocardiogram, or ECG and sometimes referred to as an EKG is the recording of electrical activity in the heart by placing electrodes at specific points on the skin from which a composite recording is produced in the form of a graph. Many lives have been saved through the help of this test as it provides an accurate human heart status.

Basically, the cardiac conduction system controls the generation and propagation or continuation and movement of electrical action potentials that cause the heart’s muscles to contract and the heart to pump blood. A normal heartbeat begins in the right atrium with a potential signal from the sinoatrial or SA node or commonly referred to as the human heart’s natural pacemaker. These signals coming from the SA node spreads to both atria which will eventually cause the muscle cells to contract or depolarize, activating a phase known as atrial systole.

An electrocardiogram is primarily conducted to check heart functions and commonly used as one of the first tests for patients suffering from chest pain or even shortness of breath. It can help determine whether the pain is due to the narrowing of blood vessels to the heart muscle or if there is an acute myocardial infarction present. If your physician suggests to run this type of test, he is looking to find two major types of information from your heart:

  1. Your heart’s activity- whether it is normal, fast, slow, or irregular. Your doctor can determine your heart’s activity by assessing how long the electrical wave travels through the heart by calculating the time intervals on the ECG.

For cases such as bradycardia, the heart rates generated by the SA node is less than 50 beats per minute which is lower than the normal heart rate while in cases of tachycardia, the SA node performs a heart rate faster than 100 beats per minute which is way above the average.

  1. The second type of information will be calculated by evaluating the extent of electrical activity passing through the heart muscle. This form of ECG test will help your cardiologist check if your heart or part of it is enlarged or is exhausted.


How Does Electrocardiogram Work

The electrocardiogram is a diagnostic tool commonly used mostly by cardiologists in studying the electrical and muscular functions of the heart by analyzing the components of the waveform. Electrocardiogram  includes the assessment of rhythm, observing P-wave forms, calculating heart rate, measurement of ECG intervals and segments and the evaluation of other relevant waves.

The procedure is fairly simple, noninvasive and it is a known fact that no pain or any sort of risk is associated with it as electrocardiogram merely records your heart’s activity and doesn’t actually send electricity into the body. The only crucial part of the test is the analysis of the electrocardiogram tracing as it requires professional training.

In conducting the test, your physician will attach a total of ten (10) electrodes with adhesive pads on your body to detect electrical impulses generated by the heart. The electrodes that are placed on different parts of your body allows 12 electrical views of the heart. Four (4) of these physical leads are attached to your limbs. These electrodes are abbreviated as LA for left arm, LR for RA for right arm, LL for the left leg and LR for the right leg. The remaining six physical leads or electrodes will be attached to your chest. For male patients, it is advisable to have your chest hair shaved before the procedure to have a better connection.

The main purpose of attaching these physical lead to your body is to get an ECG Lead. An ECG lead is a mathematically determined data which is calculated from a combination of these physical leads that are attached to your body. These physical leads are the most important part of the equipment as each electrode serves an eye that looks at the heart from a different angle.

Unlike a chest X-ray, electrocardiogram cannot produce images of your heart, blood vessels, lungs, airways, and the bones of your chest and spine. Instead, electrocardiogram sees the heart electrically – whether there is electrical depolarization or repolarization occurring in the direction of each lead or the  flow of cardiac action potentials through the heart.

After attaching all the electrodes to your body, your physician will ask you to lie flat while they are doing the whole procedure. The data of electrical impulses gathered by the electrodes connected to your body will be registered to a computer as a picture on a graph paper. After the procedure, which normally takes not more than 30 minutes, your physician will remove the electrodes attached to your body and the result which is the printed view of the recordings or the electrocardiogram will be kept as a reference for any future medical test that will be conducted to you.