The electrocardiogram (ECG or EKG) is a noninvasive test that is used to reflect underlying heart conditions by measuring the electrical activity of the heart. By positioning leads (electrical sensing devices) on the body in standardized locations, information about many heart conditions can be learned by looking for characteristic patterns on the EKG.
No special patient preparation is required for an EKG test. During the test, you will lie on an exam table and a technician will place several small sensors on your chest, arms and legs. These sensors have wires called leads which connect to the electrocardiogram machine. They create a 3D map of your heart's natural electrical rhythms, which can immediately show whether you have any unusual heart activity. The sensors don't deliver any electrical current; they only record your body's own natural heart rhythms. The test lasts for six seconds, and the results are printed out and can be interpreted immediately.
This test primarily checks the rhythmic behavior of different chambers of your heart. By measuring the time interval of the ECG a doctor can determine how long it is taking an electrical wave to pass through your heart. This shows if the electrical activity is normal, fast, slow or irregular. It also measures the amount of electrical activity passing through the heart which helps your cardiologist find out if your heart is enlarged or is overworked.
An EKG can help physicians diagnose a real-time emergency, such as a heart attack in progress, but it can also help detect patterns that emerge over time. For example, if you have high blood pressure, the EKG may show that your heart has become enlarged due to the extra work of pumping blood under higher pressure. EKGs can also detect when the electrolyte levels in your blood are too high or too low, as those variations change the heart's conductivity. Finally, the test can identify changes in your heart that occurred as a result of a past heart attack. This is important because some people may have had a heart attack without their knowledge and the EKG can show the presence of cardiac damage that requires treatment.
In some cases, especially if you have intermittent symptoms, a six-second snapshot of heart activity doesn't provide enough information. Small portable EKG machines (called "Holter Monitors") can be carried in a bag or backpack and provide a continuous record over the course of 24 hours. During such a test period, you can do almost anything you normally would, except for bathing or showering.
It's important to be aware that a normal EKG doesn't definitively rule out all cardiac issues, and your physician may suggest further types of testing. These may include a cardiac stress test or nuclear stress test.