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Echocardiogram (ECHO)
Echocardiography uses sound waves to create an image of the heart in motion. Echos are an extremely useful tool for evaluating cardiomyopathy and are used to:
- Measure the dimensions and shape of the heart
- Measure the pumping and relaxing functions of the heart
- Measure pressure gradients in the valves and vessels in and around the heart
- Evaluate the degree of obstruction, if any, within the heart
- Visualize blood flow and valve leakage
- Evaluate the condition of the valves
- Identify abnormal blood flow patterns
Echocardiography relies on the same sound wave-based technology used in prenatal sonograms and depth finders on boats. A small device that looks like a microphone, called a transducer or probe, directs ultrasound waves into the chest. The sound waves, which are inaudible to the human ear, travel into the chest and "bounce back" to a receiver, called an echocardiograph. The returning sound waves are analyzed by a computer to generate images that can be viewed on a video screen.
The information collected by the echocardiograph can be displayed three different ways:
The M-mode echocardiogram looks nothing like a heart. This abstract image is used to measure the size of various structures in the heart and the exact thickness of the heart muscle.
The 2-D echocardiogram provides snapshots of how well all the parts of the heart are working. These two-dimensional images cut through the heart, analogous to slices from a loaf of bread.
The Doppler echocardiogram helps doctors evaluate the blood flow paths through the heart. The "whoosh" sound heard during the procedure is the echocardiograph's interpretation of blood flowing past the heart's various structures.
No preparation is needed for the standard transthoracic echocardiogram, which usually takes one to two hours to complete. Electrodes are attached to the chest to monitor the heart's electrical activity during the test. A technician applies a watery gel to the chest and then slides the transducer across the chest to scan the heart from various angles. In some cases, a contrasting agent or dye is injected into a vein to improve the images from the echo. Most patients say that the procedure is painless, although some report slight discomfort from the pressure of the transducer on the chest.
Other types of echocardiograms that may be used to evaluate cardiomyopathy include:
Transesophageal echocardiogram. For more detailed information about the heart valves and possible blood clots in the heart, a transesophageal echocardiogram or TEE may be necessary. In this procedure, the transducer is mounted on the tip of a half-inch-diameter, flexible tube that is inserted through the patient's mouth down into the esophagus, the passageway that runs from the throat to the stomach. The advantage of the transesophageal echocardiogram is that it provides a more detailed image of the heart valves and blood flow because the esophagus is close to the heart.
Patients are asked to fast for at least eight hours before the test; ask your physician about taking medications. This procedure does not interfere with breathing, and patients are given a numbing medication and a mild sedative to make them more comfortable. Most patients rest comfortably during the procedure, which usually lasts between 15 and 20 minutes. Some individuals experience a minor sore throat following this procedure.
Stress Echocardiogram. A stress echocardiogram is done under conditions that increase the workload on the heart to determine its pumping capacity and efficiency and to evaluate any blockages of the coronary arteries. Patients undergoing a stress echo are asked to fast for three hours before the exam, wear comfortable clothing, and take medications as usual unless otherwise instructed.
The stress echo starts by obtaining images of the heart at rest. Then, depending on the type of stress echocardiogram being performed, the technician will take additional images after the workload of the heart has been increased. For an exercise stress test, patients walk on a treadmill or pedal a stationary bicycle to reach their peak exercise level. For patients who are unable to exercise, a medication is injected to simulate the effects of exercise on the heart, usually dobutamine. Dobutamine causes the heart rate to gradually increase. After receiving the drug, some people experience a slight flushing in the cheeks, a tingling scalp, and the uncomfortable feeling that their heart is beating faster and harder. Alternatively, the medication atropine may be used, but it has potentially serious side effects for people with undiagnosed glaucoma.
Although echocardiography uses ultrasound, which poses no known risk to the body, a stress test is not completely risk free. On rare occasions, a heart problem can occur during a stress test. To detect any problems that may arise, blood pressure and the heart's electrical activity are monitored continuously throughout the test. The technicians administering the test are trained to treat potential complications.
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