The electrocardiogram (ECG or EKG) is a diagnostic tool that is routinely used to assess the electrical and muscular functions of the heart. While it is a relatively simple test to perform, the interpretation of the ECG tracing requires significant amounts of training. Numerous textbooks are devoted to the subject.

The heart is a two stage electrical pump and the heart's electrical activity can be measured by electrodes placed on the skin. The electrocardiogram can measure the rate and rhythm of the heartbeat, as well as provide indirect evidence of blood flow to the heart muscle.

A standardized system has been developed for the electrode placement for a routine ECG. Ten electrodes are needed to produce 12 electrical views of the heart. An electrode lead, or patch, is placed on each arm and leg and six are placed across the chest wall. The signals received from each electrode are recorded. The printed view of these recordings is the electrocardiogram.

By comparison, a heart monitor requires only three electrode leads – one each on the right arm, left arm, and left chest. It only measures the rate and rhythm of the heartbeat. This kind of monitoring does not constitute a complete ECG.

Types

       An EKG records a picture of your heart’s electrical activity for the time that you’re being monitored. However, some heart problems come and go. In these cases, you may need longer or more specialized monitoring.

• Stress test

Some heart problems only appear during exercise. During stress testing, you’ll have an EKG while you’re exercising. Typically, this test is done while you’re on a treadmill or stationary bicycle.

• Holter monitor

Also known as an ambulatory ECG or EKG monitor, a Holter monitor records your heart’s activity over 24 to 48 hours while you maintain a diary of your activity to help your doctor identify the cause of your symptoms. Electrodes attached to your chest record information on a portable, battery-operated monitor that you can carry in your pocket, on your belt, or on a shoulder strap.

• Event recorder

Symptoms that don’t happen very often may require an event recorder. It’s similar to a Holter monitor, but it records your heart’s electrical activity just when symptoms occur. Some event recorders activate automatically when they detect symptoms. Other event recorders require you to push a button when you feel symptoms. You can send the information directly to your doctor over a phone line.

Risks

There are few, if any, risks related to an EKG. Some people may experience a skin rash where electrodes were placed, but this usually goes away without treatment.

People undergoing a stress test may be at risk for heart attack, but this is related to the exercise, not the EKG.

An EKG simply monitors the electrical activity of your heart. It doesn’t emit any electricity and is completely safe.

How to prepare for an Electrocardiogram (ECG or EKG)?

                   Avoid drinking cold water or exercising before your EKG. Drinking cold water can cause changes in the electrical patterns that the test records. Exercise can increase your heart rate and affect the test results.

Interpreting the results of an EKG

If your EKG shows normal results, your doctor will likely go over them with you at a follow-up visit.

Your doctor will contact you immediately if your EKG shows signs of serious health problems.

An EKG can help your doctor determine if:

• your heart is beating too fast, too slow, or irregularly

• you’re having a heart attack or you’ve previously had a heart attack

• you have heart defects, including an enlarged heart, a lack of blood flow, or birth defects

• you have problems with your heart’s valves

• you have blocked arteries, or coronary artery disease

Your doctor will use the results of your EKG to determine if any medications or treatment can improve your heart’s condition.