What to Expect From an Electrocardiogram (EKG or ECG)

An electrocardiogram, also referred to as ECG or EKG, is a non-invasive test that monitors and records the electrical activity of your heart as it beats. Abnormalities in the expected electrical pattern, as displayed on a graph, can help diagnose different types of heart problems, such as atrial fibrillation, angina, and heart attack.

An ECG can also help establish if you are at risk of heart disease or monitor your response to treatment for a heart condition.

This article explains what an electrocardiogram is used for, how it is performed, and what to expect before, during, and after the test.

Purpose of an EKG Test

An electrocardiogram records your heart's electrical activity. With each heartbeat, the ECG will produce a consistent pattern of jagged lines on a continuous readout called a tracing. If the pattern is not consistent or falls out of the expected pattern, it could indicate that you have a heart problem.

A healthcare provider might order an ECG as part of a yearly physical examination or to screen for heart disease if:

• You have risk factors for heart disease, such as smoking, obesity, a family history of heart disease, high blood pressure, diabetes, or high cholesterol.
• You have signs of a heart condition, like chest pain, heart palpitations, lightheadedness, fainting, or swollen feet and ankles (edema).
• You have signs of a stroke or "mini-stroke," such as sudden slurring and numbness or paralysis on one side of the body.

An ECG can help determine the extent of damage if you have a heart attack and even predict your risk of a future heart attack.

An ECG may also detect heart rhythm problems like tachycardia (rapid heartbeats) or bradycardia (slowed heartbeats) so that further tests can be ordered to determine the cause.

If you are diagnosed with conditions like coronary artery disease, heart failure, or atrial fibrillation, you may need periodic ECGs to check if you are stable and/or responding to treatment.

Types of ECG

There are three major types of ECG that have different purposes and applications:

• Resting ECG: This is the standard form of ECG that is performed when you are lying down. In addition to screening for heart disease, it can monitor your heart during surgery.
• Ambulatory monitoring: This involves an ECG device that you wear on your body for 24 hours to detect problems that may only happen occasionally, like heart palpitations.
• Cardiac stress testing; This involves the monitoring of your heart while you are on a treadmill or stationary bike to determine the effects of exercise on your heart. This can detect heart problems that don't occur at rest.

What Are the Risks and Limitations?

The ECG is one of the most common tests in medicine because it can screen for a wide variety of heart conditions. The devices are available in most medical facilities and are relatively safe, simple, and inexpensive to perform.

Possible risks of ECG include:

• Irritation or an allergic reaction to the adhesive electrodes attached to your arms and chest
• Tissue breakdown due to the prolonged use of the electrodes during an ambulatory ECG
• Lightheadedness, fainting, or other heart-related events (including a heart attack) while performing a stress test
  

An ECG also has certain limitations. Among them:

• A resting ECG can only detect problems during the tracing and some, like tachycardia, occur only intermittently. An ambulatory ECG may be needed if a resting ECG fails to detect a suspected problem.
• An ECG can deliver a normal or near-normal reading with many types of heart disease, such as coronary artery disease. Other tests, like angiography, may be needed to detect these conditions.
• ECGs may not be diagnostic of any condition on their own. Sometimes, an abnormality spotted on an ECG may end up having no medical significance after a thorough evaluation.
  

Before the ECG Test

There is not much preparation needed for an ECG.

Before the test, you will be asked to remove your top so that a series of electrodes can be applied to your body. A hospital gown will be provided. If you are undergoing a cardiac stress test, you may be asked to bring a tracksuit or similar gear to wear.

Depending on the goals of the test, you may need to stop certain medications temporarily. Inform your healthcare provider about any medications you take, including over-the-counter drugs, prescription medications, or recreational drugs. These may impact the results or the interpretation of the results.

An ECG is covered by most health insurance plans, but check with your provider just to be sure.

During the ECG

An ECG can be performed in a clinic, hospital, or provider's office by a nurse, technician, or physician.

Once you are changed into a hospital gown, you will lie down on an examination table. A total of 10 adhesive electrodes will be applied to your body: one on each arm and leg and six on your chest.

Each electrode is attached to the ECG machine equipped with a digital display and printer. Once the device is turned on, it will record the electrical activity of your heart, which can be viewed on the digital display. During or at the end of the test, the printer will produce the tracer.

The ECG reading will take about five minutes. During that time, you will be asked to remain still as movement can disrupt the pattern. There is no pain or discomfort associated with an ECG.

After the ECG

After the test, the electrodes are removed. Any adhesive still attached to the skin can easily be removed with an alcohol pad. You may experience some tugging of hair as the electrodes are taken off, but technicians are usually very careful about this. You can then remove the gown and put your clothes back on.

From start to finish, an ECG takes around 15 minutes (not including the waiting time in the reception). You should not have any side effects, and there are no limitations on your activity afterward.

Rarely, the adhesive can cause allergic reactions, which may not appear until up to 24 hours after the test. If you experience a rash, call your healthcare provider.

Interpreting the ECG Results

An ECG uses 10 cables that generate 12 different tracers. Each tracer shows the electrical activity from different angles of the heart.

In healthy people, a tracing will consist of a specific pattern that falls within an expected range. This not only includes the up-and-down waves (called the P wave, QRS complex, ST segment, and T wave) but also the spaces in between them (called a PR interval and QT interval).

If the pattern falls outside of the expected value, you may have a heart problem, such as:

• Cardiac arrhythmias: These are heart rhythm problems that include tachycardia, bradycardia, and atrial fibrillation.
• Conduction disorders: Also known as heart block, this occurs when the electrical system of the heart fails to produce or deliver certain signals. An example is long QT syndrome.
• Myocardial infarction: This is the term for a heart attack. An ECG can not only detect a current heart attack but may also detect a prior "silent" heart attack that was undiagnosed.
• Angina: This is chest pain caused by reduced blood flow to the heart. This includes stable angina(which can often be managed) and unstable angina (which may be a sign of a heart attack).
• Hypertrophic cardiomyopathy: This occurs when the heart muscle is abnormally enlarged. On an ECG, the tracer will show a downward-sloping ST segment from the chest electrodes.
• Congenital heart disease: These are defects that develop in a fetus during pregnancy, such as a ventricular septal defect (a "hole in the heart").
• Electrolyte imbalances; Electrolytes like potassium and magnesium enable the conduction of electrical signals to the heart, If there are any imbalances, these will be seen in the T waves.
• Heart infections: Infections like pericarditis, myocarditis, and endocarditis will cause abnormalities in the ST segment.

Your ECG report may have a description of the wave pattern but is unlikely to describe your heart condition in detail. Your healthcare provider will need to take your symptoms and medical history into account when determining whether or not you have a heart condition

Follow-Up

While the ECG can diagnose some heart conditions on its own (such as cardiac arrhythmias), it is more often used as a preliminary screening test. In many cases, abnormalities seen on a tracer will need to be followed with other tests to render a definitive diagnosis.

For instance, If the ECG suggests coronary artery disease, cardiac catheterization might be used to confirm a blocked blood vessel. If hypertrophic cardiomyopathy is suspected, an imaging test called an echocardiogram may be ordered to view the size of the heart.

Summary

An electrocardiogram (ECG or EKG) is a common test that measures the electrical activity of your heart during heartbeats. Based on the pattern of lines on the read-out, called a tracer, a healthcare provider may be able to diagnose a heart condition, predict the risk of a heart attack, or monitor your response to heart medications.

The test involves the placement of 10 electrodes on your chest and arms, which are then connected the main ECG machine. From start to finish, the test takes around 15 minutes.