Written by Daria Sysoeva | Edited by Alexander Alva
Photo by Towfiqu Barbhuiya
When a patient is experiencing symptoms such as chest pain, fainting, or an irregular heartbeat, an ECG test is required to evaluate the health of the heart. The results of the ECG can reveal conditions such as arrhythmia (irregular heart rhythm), cardiomyopathy (thickening of the heart muscle), and myocardial infarction (heart attack). This article will define what an ECG is, when it is used, and what it can diagnose [1].
An electrocardiogram (ECG) is a medical test that tracks changes in electrical activity of the heart as it beats [2]. During this test, the patient lies down while the medical professional places sticky patches called electrodes on the patient. The electrodes are connected to an ECG machine, which records the output. In a 12-lead ECG, the patches are placed around the heart, on the lower legs, and on the forearms [1]. The ECG machine records a wave-like pattern, depicting how the chambers of the heart contract. The first wave of the ECG is called the P wave, which indicates how electrical signals spread throughout the upper chambers of the heart, or the atria. Next, the QRS complex, the largest spike on the ECG, shows how the atria contract to pump blood throughout the heart and spread the electrical activity to the heart’s lower chambers, called the ventricles. Following the QRS complex, the T wave indicates that there is no more spread of electrical activity after the ventricles contract [3].
To test how well the heart works under physiological stress, a special type of ECG test called a stress ECG test is performed. In this test, electrodes are once again placed on the patient but, this time, the patient is told to walk or jog on a treadmill until the point of exhaustion. During the exam, the medical professional will ask the patient if they feel any chest pain, shortness of breath, or lightheadedness. The patient will then follow the Bruce protocol: exercising in 3-minute intervals, with each interval requiring an increase in exercise intensity. After the exercise regimen is complete, the patient completes a cool-down exercise while their ECG is monitored to determine when their heart rate is back to normal [4].
An ECG is an important part of physical exams and preoperative medical clearances. The different waves on the ECG and the spaces between each wave complex show how consistently the heart is beating. If the spaces between each wave complex are not symmetrical, the patient has arrhythmia, or an irregular heart rhythm. Overall, an ECG offers a detailed look into how well the heart is functioning.
References:
2. Sattar, Y., Chhabra, L. (2022). Electrocardiogram. National Library of Medicine.
4. Vilcant, V., Zeltser, R. (2022). Treadmill Stress Testing. National Library of Medicine.