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.
Echocardiography (echo) is painless; the test usually takes less than an hour to do. For some types of echo, your doctor will need to inject saline or a special dye into one of your veins. The substance makes your heart show up more clearly on the echo pictures.The dye used for echo is different from the dye used during angiography (a test used to examine the body’s blood vessels). For most types of echo, you will remove your clothing from the waist up. Women will be given a gown to wear during the test. You’ll lie on your back or left side on an exam table or stretcher.
Soft, sticky patches called electrodes will be attached to your chest to allow an EKG(electrocardiogram) to be done. An EKG is a test that records the heart’s electrical activity. A doctor or sonographer (a person specially trained to do ultrasounds) will apply gel to your chest. The gel helps the sound waves reach your heart. A wand-like device called a transducer will then be moved around on your chest. The transducer transmits ultrasound waves into your chest. A computer will convert echoes from the sound waves into pictures of your heart on a screen. During the test, the lights in the room will be dimmed so the computer screen is easier to see.
The illustration shows a patient having echocardiography. The patient lies on his left side. A sonographer moves the transducer on the patient’s chest, while viewing the echo pictures on a computer.
The sonographer will record pictures of various parts of your heart. He or she will put the recordings on a computer disc for a cardiologist (heart specialist) to review.
During the test, you may be asked to change positions or hold your breath for a short time. This allows the sonographer to get better pictures of your heart.
At times, the sonographer may apply a bit of pressure to your chest with the transducer. You may find this pressure a little uncomfortable, but it helps get the best picture of your heart. You should let the sonographer know if you feel too uncomfortable.
The process described above is similar to the process for fetal echo. For that test, however, the transducer is placed over the pregnant woman’s belly at the location of the baby’s heart.
Transesophageal echo (TEE) is used if your doctor needs a more detailed view of your heart. For example, your doctor may use TEE to look for blood clots in your heart. A doctor, not a sonographer, will perform this type of echo.
TEE uses the same technology as transthoracic echo, but the transducer is attached to the end of a flexible tube.
Your doctor will guide the tube down your throat and into your esophagus (the passage leading from your mouth to your stomach). From this angle, your doctor can get a more detailed image of the heart and major blood vessels leading to and from the heart. For TEE, you’ll likely be given medicine to help you relax during the test. The medicine will be injected into one of your veins. Your blood pressure, the oxygen content of your blood, and other vital signs will be checked during the test. You’ll be given oxygen through a tube in your nose. If you wear dentures or partials, you’ll have to remove them.
The back of your mouth will be numbed with gel or spray. Your doctor will gently place the tube with the transducer in your throat and guide it down until it’s in place behind your heart. The pictures of your heart are then recorded as your doctor moves the transducer around in your esophagus and stomach. You shouldn’t feel any discomfort as this happens. Although the imaging usually takes less than an hour, you may be watched for a few hours at the doctor’s office or hospital after the test.
Stress echo is a transthoracic echo combined with either an exercise or pharmacological (FAR-ma-ko-LOJ-ih-kal) stress test.
For an exercise stress test, you’ll walk or run on a treadmill or pedal a stationary bike to make your heart work hard and beat fast. For a pharmacological stress test, you’ll be given medicine to increase your heart rate.
A technician will take pictures of your heart using echo before you exercise and as soon as you finish. The Health Topics Stress Testing article provides more information about what to expect during a stress test.
As the doctor or sonographer moves the transducer around, you will see different views of your heart on the screen of the echo machine. The structures of your heart will appear as white objects, while any fluid or blood will appear black on the screen.
Doppler ultrasound often is used during echo tests. Doppler ultrasound is a special ultrasound that shows how blood is flowing through the blood vessels.
This test allows the sonographer to see blood flowing at different speeds and in different directions. The speed and direction of blood flow appear as different colors moving within the black and white images. The human ear is unable to hear the sound waves used in echo. If you have a Doppler ultrasound, you may be able to hear “whooshing” sounds. Your doctor can use these sounds to learn about blood flow through your heart.
A Holter monitor is a small of portable, battery-powered medical device that measures the heart’s activity such as rate and rhythm). This testing is ordered when your doctor needs more information about the functioning of your heart than a routine electrocardiogram (EKG) can give him or her.
Holter monitoring (24h) refers to a 24-hour, continuous test to record your heart rate and rhythm. This device has electrodes and electrical leads exactly like a regular electrocardiogram. A patient wears the Holter monitor for 12 to 48 hours as they go about their normal daily routines. Holter monitor testing is also sometimes called ambulatory electrocardiography.
An electrocardiogram is a medical test that is typically ordered to measure heart rate and rhythm and to look for other abnormalities that may affect normal heart function. However, patients may experience heart rhythm irregularities that do not show up at the time the electrocardiogram is done. In these cases, if an irregular heartbeat (arrhythmia) is suspected, your doctor may order a Holter monitor test.
The Holter monitor lets your doctor see how your heart functions on a long-term basis. The recordings made by the monitor help your doctor determine if your heart is getting enough oxygen or if the electrical impulses in the heart are delayed.