Echocardiography

A echocardiographic view of the heart's four chambers. Source: Wikimedia Commons

Echocardiography is a test that uses sound waves to create images of the heart. It provides information about the size and shape of the heart and the level of function of its chambers and valves.

The test also can identify areas of heart muscle that are not pumping normally due to poor blood flow or injury from previous heart attacks. In addition, a type of echocardiography called Doppler ultrasound shows how well blood flows through the chambers and valves of the heart. Echocardiography can detect blood clots inside the heart, fluid buildup in the sac around the heart (pericardium), and problems with the aorta (the main artery that carries oxygen-rich blood out of the heart).

Other Names for Echocardiography

Other names for echocardiography include:

• Ultrasound of the heart
• Echo
• Surface echo

Why Echocardiography is Done

Echocardiography is done to see the size, structure, and movement of the different parts of the heart, including the valves, the septum (the wall separating the chambers on the right and left sides of the heart), and the walls of the heart chambers. The Doppler ultrasound technique shows the movement of blood through the heart.

Echocardiography can be used to:

• Diagnose heart problems
• Guide or determine next steps for treatment
• Monitor changes and improvement
• Determine the need for additional tests

Doctors use echocardiography to provide information about:

• Heart size: An enlarged heart can be the result of high blood pressure, leaky heart valves, or congestive heart failure.
• Heart muscles that are weak and aren't moving (pumping) properly: Weakened areas of heart muscle can be due to damage from a heart attack. Weakening could also mean that the area isn't getting enough blood supply, which can be due to coronary artery disease.
• Problems with the heart's valves: Echocardiography can show whether any of the valves of the heart don't open normally or don't form a complete seal when closed. It can also show whether there are infections on the heart valves, such as in bacterial endocarditis. Infections are often visible as masses on the valves, known as vegetations.
• Abnormalities in the heart's structure: Echocardiography can detect a variety of heart abnormalities, such as a hole in the septum (the wall that separates the two chambers on the left side of the heart from the two chambers on the right side) and other congenital heart defects (structural problems present at birth).
• The pressure within the chambers of the heart: This can be helpful in people with lung disorders to help to see how much they are affecting the heart and the blood flow through the lungs. Bad lung disease can cause heart failure, a condition called cor pulmonale.
• The aorta: The aorta is the biggest blood vessel leading out of the heart to the rest of the body. Echocardiography is commonly used to assess and detect problems with the aorta such as an aneurysm (abnormal bulge or ballooning in the wall of an artery).
• Blood clots or tumors: After a stroke, echocardiography might be done to check for blood clots or tumors that may have caused it.
• Chest pain, breathing problems, or heart murmurs: Echocardiography can help sort out the many possible causes of these problems.
• Readiness for surgery: Echocardiography is helpful in determining whether a person's heart is healthy enough to withstand an operation.

Types

There are several types of echocardiography, but they all use sound waves to create images of the heart. This is the same ultrasound technology that allows doctors to see an unborn baby inside a pregnant mother. Unlike x-rays and some other tests, echocardiography doesn't involve radiation. It is one of the safest tests that exist and there are no known side effects.

Transthoracic echocardiography

Transthoracic echocardiography is the most common type of echocardiogram. It is almost painless, and noninvasive. Noninvasive means that no surgery is done and no instruments are inserted into the body.

This type of echocardiography involves placing a device called a transducer on the chest that sends special sound waves, called ultrasound, through the chest wall to the heart. Ultrasound waves cannot be heard by the human ear because they are so high-pitched. As the ultrasound waves bounce off the structures of the heart, a computer in the echo machine converts them into pictures on a screen. In echocardiography, the ultrasound machines can also use a special technique called Doppler flow study. This measures the sound waves as they bounce back from moving blood. The direction of movement of the blood slightly changes the pitch of the sound detected by the machine. Using this technique, the echocardiogram can see the direction of blood flow.

Stress echocardiography

Stress echocardiography is a transthoracic echo that is done as part of a cardiac stress test. During a cardiac stress test, the person exercises or takes medicine (given by the doctor) to make the heart pump harder and beat faster. Some heart problems, such as coronary artery disease, are easier to diagnose when the heart is beating fast and pumping hard.

Transesophageal echocardiography

With standard transthoracic echocardiography (see above), it can be difficult to see the aorta and certain other parts of the heart. If the doctor needs a better look at these areas, he or she may recommend transesophageal echocardiography (TEE).

In this test, the transducer is attached to the end of a flexible tube that is guided down the throat and into the esophagus (the tube leading from the mouth to the stomach) to get a more detailed image of the heart.

Fetal echocardiography

Fetal echocardiography is used to look at an unborn baby's heart. A doctor may recommend this test to check the baby for heart problems. Fetal echocardiography is commonly performed during pregnancy at about 18 to 22 weeks.

Preparation

In general, no special preparation is needed before echocardiography. Usually the patient can eat, drink, and take any medicines as he or she normally would. The exception is if a transesophageal echocardiography (TEE) is being done. This test usually requires that the person not eat or drink for 8 hours prior to the test.

Prior to stress echocardiography, there may be special preparations. The doctor will advise a patient on how to prepare.

How Echocardiography Is Done

Usually, echocardiography is painless and takes less than an hour to perform. For some tests, the doctor will need to inject saline or a special dye into the vein that makes the heart show up more clearly on the test images. This special dye is different from the dye used during an angiogram test.

Transthoracic echocardiography

The patient undresses from the waist up. Women are given a gown to wear during the procedure. The patient lies on his back or left side on an exam table or stretcher.

EKG electrodes are attached to the chest with stickers to allow an EKG to be done. (The EKG is painless.) A doctor or sonographer (a person specially trained to do ultrasounds) applies a gel to the patient's chest that helps the sound waves reach the heart. (The gel may be chilly and uncomfortable, but often it is warmed to prevent this.) A wand-like device called a transducer is placed on the chest and moved around.

The transducer transmits ultrasound waves into the chest. Echoes from the sound waves are converted into pictures of the heart on a computer screen. During the test, the lights in the room are dimmed so the computer screen is easier to see.

The sonographer makes several recordings of the images to show different locations in the heart. The recordings are put on a computer disc or videotape for the cardiologist (heart doctor) to review.

During the test, the patient may be asked to change positions or hold his breath for a short time so that the sonographer can get good pictures of the heart. At times, the sonographer may apply pressure to the chest for a few moments with the transducer. This pressure can be uncomfortable, but it helps the sonographer get clearer pictures of the heart. This pushing is the only way that a transthoracic echo might be uncomfortable or painful. There is no shock sensation or electricity.

Transesophageal echocardiography

Transesophageal echocardiography (TEE) is used when the doctor needs a more detailed view of the heart. This may be necessary to look for blood clots in the heart or if transthoracic echocardiography doesn't provide a good enough view of certain parts of the heart. A doctor, not a sonographer, performs this type of echocardiography.

The test uses the same technology as transthoracic echocardiography, but the transducer is attached to the end of a flexible tube. The tube is guided down the throat and into the esophagus (the tube leading from the mouth to the stomach) to get a more detailed image of the heart and major blood vessels leading to and from the heart.

For TEE, patients are generally given medicine through an IV (needle inserted in a vein) to prevent anxiety during the test. Blood pressure, oxygen content of the blood, and other vital signs are monitored during the test. The patient receives oxygen through a tube to the nose. Dentures or partials need to be removed during the test.

The back of the mouth is numbed with a gel or a spray to prevent the gag reflex when the transducer is put down the throat. The spray may taste bad. The tube with the transducer on the end is gently placed in the throat and guided down until it is in place behind the heart. Images of the heart are then recorded as the doctor moves the transducer around in the esophagus and stomach. Because of the anxiety medication, the patient should not feel any discomfort as this happens. Although the imaging usually takes less than an hour, the patient may be monitored for a few hours at the doctor's office or hospital after the test.

Stress echocardiography

Stress echocardiography is a transthoracic echocardiogram combined with either an exercise or chemical stress test. For an exercise stress test, the patient walks or runs on a treadmill or pedals a stationary bicycle to make his heart beat fast and pump hard. For a chemical stress test, the patient is given medicine to make the heart beat fast and pump hard.

Fetal echocardiography

Fetal echocardiography is similar to transthoracic echocardiography, except that the transducer is placed on the mother's belly over the location of the developing baby's heart.

What to expect

As the doctor or sonographer moves the transducer around, different views of the heart can be seen on the screen of the echocardiography machine. The structures of the heart will appear as white objects, while any fluid or blood will appear black on the screen.

Doppler ultrasound techniques are often used during echocardiography tests. Doppler ultrasound is a special ultrasound that shows how blood is flowing through the blood vessels. This allows the sonographer to see the blood flowing in different speeds and directions. The speeds and directions appear as different colors moving within the black and white images.

The human ear is unable to hear the sound waves used in echocardiography. If Doppler ultrasound is used, however, a“ whooshing” sound may be heard as the echocardiography machine converts the echoes into sounds that can be heard and which the doctor can use as information about the flow of blood through the heart.

After echocardiography

A patient can usually can go back to normal activities immediately after the test. He may not be able to drive after a transesophageal echocardiography. The doctor will let patients know whether they need to arrange for someone to take them home.

Results of Echocardiography

The doctor will look for healthy heart valves and chambers, as well as normal movement of the heart wall. Variations provide information about many aspects of heart health, including:

Heart size

Weakened or damaged heart valves, high blood pressure or other diseases can cause the chambers of the heart to enlarge. The doctor can use an echocardiogram to evaluate the need for treatment or monitor treatment effectiveness.

Pumping strength

An echocardiogram can help the doctor determine the heart's pumping strength. Specific measurements may include the percentage of blood that is pumped out of a filled ventricle with each heartbeat (ejection fraction) or the volume of blood pumped by the heart in one minute (cardiac output). If the heart isn't pumping enough blood to meet the body's needs, heart failure may be a concern.

Damage to the heart muscle

During an echocardiogram, the doctor can determine whether all parts of the heart wall are contributing equally to the heart's pumping activity. Parts that move weakly may have been damaged during a heart attack or may be receiving too little oxygen. This may indicate coronary artery disease or various other conditions.

Valve problems

An echocardiogram shows how the heart valves move as the heart beats. The doctor can determine if the valves open wide enough for adequate blood flow or close fully to prevent blood leakage. Abnormal blood flow patterns and conditions such as aortic valve stenosis—when the heart's aortic valve is narrowed—can be evaluated as well.

Structural abnormalities

Many structural problems can be detected with an echocardiogram, including problems with the heart chambers, abnormal connections between the heart and major blood vessels, and complex heart defects that are present at birth. Echocardiograms can even be used to assess a baby's heart before birth.

Benefits

If images of the heart need to be obtained, echocardiography has many advantages over alternative methods. Some of these advantages are as follows.

• Usually no dyes are required.
• Usually no sedatives are required (except for transesophageal echocardiographs).
• There is nothing claustrophobic about the equipment.
• The technology is widespread and available in most hospitals.
• There is no radiation exposure.

Risks

There are no risks associated with transthoracic or fetal echocardiography. In transesophageal echocardiography, there are some risks associated with the medicine given to help the patient relax. These include a bad reaction to the medicine, difficulty breathing, or nausea. The patient's throat might be sore for a few hours after the test. On rare occasions, the tube can cause a minor throat injury.

There are risks associated with stress echocardiography, but these are related to the exercise or medicine used to raise the heart rate, not to the echocardiography part of the test. Serious complications from cardiac stress tests are very uncommon.

External Links

Medline Plus: Echocardiography Stress Test Tutorial

Yale Atlas of Echocardiography

American Society of Echocardiography: See My Heart

American Heart Association: What is echocardiography?