Echocardiogram

    Cardiac ultrasonography (echocardiography) is a valuable non-invasive tool for imaging the heart and surrounding structures. It can be quite helpful in establishing a specific diagnosis and estimating the severity of various cardiac diseases. It is important to recognize, however, that the ultrasound exam is only a part of the complete cardiac work-up.

    Also known simply as an “echo,” an echocardiogram of the heart’s chambers and valves is called a transthoracic echocardiogram. The word “transthoracic” means “across the chest.” It is a painless test that is very similar to an x-ray but without the radiation. Instead of using x-rays, it uses high-frequency sound waves (ultrasound) to get a picture of the four heart chambers and the four heart valves.

   The sound waves bounce back from the heart chambers and valves, producing images and sounds that can be used by the physician to detect damage and disease. Because it does not involve any of the radiation that an x-ray does, it is a very safe test. In fact, it uses the same technology that is used to evaluate a baby’s health before birth.

   To do a transthoracic echocardiogram, the physician or technician prepares the chest area by applying a conductive gel. A small device called a transducer is then placed on the patient’s chest, and a picture of the area is seen immediately on a video monitor. At that time, the lights in the room may be dimmed to give a better view of the various monitors that are recording the results of the echocardiogram.

There are different types of echocardiograms, which include the following:

• One-dimensional (M-mode; motion mode). A one-dimensional view of the heart, as if a line were drawn straight through it. This can be black-and-white and/or color.
  
  
• Two-dimensional (cross-sectional). A two-dimensional view of the heart, which shows both length and width of heart structures. This can be black-and-white and/or color.
  
  
• Doppler ultrasound. A test that measures the speed (velocity) with which blood is traveling through the heart. This enables pressure gradients across valves to be assessed. For example, abnormal velocity can be interpreted as a drop in pressure across the area of a heart valve. This, in turn, may suggest the extent of valve narrowing, plaque deposit, etc.
  
  
• Stress echocardiogram. An echocardiogram that is performed while the patient exercises in a controlled manner on a treadmill or stationary bicycle at varied speeds and elevations. The wall motion of the heart’s pumping chamber before and immediately after exercise may reveal indirect evidence of a lack of blood supply to selected areas of the heart muscle.
  
  
• Chemical (e.g., dobutamine or adenosine) stress echocardiogram. A type of stress test that is used with patients who are unable to perform physical activity. A chemical stress echocardiogram measures the reaction of the heart under chemically induced stress, in order to assess the wall motion of the heart muscle. A drug such as dobutamine causes the heart to react as if the person were exercising, though the patient is actually at rest.
  
  
• Transesophageal echocardiogram (TEE). A minimally invasive echocardiogram that requires a transducer to be inserted down the patient’s throat into the esophagus (the long tube that connects the throat to the stomach). Because the esophagus is located so close to the heart, very clear images of the heart structures and valves can be obtained from the inside of the body, without the interference of the chest wall and lungs.

    Depending on which type of echocardiogram is used, an echocardiogram is either a noninvasive or minimally invasive diagnostic test used to measure the structure and function of the heart. By obtaining this information, the physician can:

• Check the health and performance of heart valves
  
• Measure the heart wall and check for abnormalities in heart wall motion
  
• Detect disease or accumulation of fluid in the pericardium
  
• Identify blood clots