An ECG, or electrocardiogram, is a medical test that measures the electrical activity of the heart. It works by attaching small electrode patches to the skin of the chest, arms, and legs. These electrodes detect the tiny electrical changes on the skin that arise from the heart muscle’s electrophysiologic pattern of depolarizing and repolarizing during each heartbeat. This electrical activity is then recorded and displayed as a waveform on a monitor or paper, providing valuable information about the heart’s function and rhythm.

An ECG is commonly used to detect and evaluate various heart conditions, such as arrhythmias (irregular heartbeats), coronary artery disease, past heart attacks and their extent, heart enlargement, and electrolyte imbalances. It can also be used to monitor the health of individuals with existing heart conditions, the effects of certain heart medications, and the function of implanted pacemakers.

The advantages of an ECG include its non-invasive nature, its simplicity and quickness in execution, and its ability to be performed almost anywhere, including in ambulances and remote settings. It provides immediate results, which are crucial for diagnosing acute heart conditions that require prompt treatment. Additionally, it is one of the most affordable tests for evaluating heart health.

No special preparation is typically needed for a standard ECG. Patients are usually asked to lie still and may be told to breathe slowly and calmly. It’s important to relax and stay warm during the test to avoid muscle tension or shivering, which can affect the results. In some cases, men might need to have small areas of their chest shaved to ensure the electrodes make secure contact with the skin.

While an ECG is a valuable tool for diagnosing many heart conditions, it does not detect all heart problems. Some heart conditions might not show up on an ECG, especially if the heart is functioning normally at the time of the test. Conditions such as intermittent arrhythmias, mild heart valve issues, or early stages of coronary artery disease might require additional tests, like an echocardiogram, stress test, or cardiac MRI for diagnosis.

An abnormal ECG can indicate a variety of heart-related issues, including arrhythmias, blocked or narrowed arteries in the heart (coronary artery disease), a past heart attack or its severity, an enlarged heart that is working under increased strain, and electrolyte imbalances affecting the heart’s electrical activity. However, an abnormal ECG result needs to be interpreted in conjunction with other clinical findings and tests by a healthcare professional to determine the exact cause and appropriate treatment.