Echocardiography

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An echocardiogram. Image shows that the human heart has four chambers. Apical view - left side of the heart to the right. Right side-up - heart's apex at bottom. The trace in the lower left shows the cardiac cycle and the red mark the time in the cardiac cycle that the image was captured.

An abnormal echocardiogram. Image shows a mid-muscular ventricular septal defect. The trace in the lower left shows the cardiac cycle and the red mark the time in the cardiac cycle that the image was captured. Colours are used to represent the velocity of the blood.

The echocardiogram is an ultrasound of the heart. Using standard ultrasound techniques, two-dimensional slices of the heart can be imaged. The latest ultrasound systems now employ 3D real-time imaging.

In addition to creating two-dimensional pictures of the cardiovascular system, the echocardiogram can also produce accurate assessment of the velocity of blood and cardiac tissue at any arbitrary point using Pulsed or Continuous wave Doppler ultrasound. This allows assessment of cardiac valve areas and function, any abnormal communications between the left and right side of the heart, any leaking of blood through the valves (valvular regurgitation), and calculation of the cardiac output as well as the ejection fraction.

Echocardiography was the first medical application of ultrasound. Echocardiography was also the first application of intravenous contrast-enhanced ultrasound. This technique injects gas-filled microbubbles into the venous system to improve tissue and blood delineation. Contrast is also currently being evaluated for its effectiveness in evaluating myocardial perfusion. It can also be used with Doppler ultrasound to improve flow-related measurements.

Echocardiography is usually performed by cardiologists or cardiac sonographers.

[edit] Transthoracic echocardiogram

The standard echocardiogram is also known as a transthoracic echocardiogram, or TTE. In this case, the echocardiography transducer (or probe) is placed on the chest wall (or thorax) of the subject, and images are taken through the chest wall. This is a non-invasive, highly accurate and quick assessment of the overall health of the heart. A cardiologist can quickly assess a patient's heart valves and degree of heart muscle contraction (an indicator of the ejection fraction). The images are displayed on a video screen, and are recorded either by videotape (analog) or by digital techniques.

An echocardiogram can be used to evaluate all four chambers of the heart. It can determine strength of the heart, the condition of the heart valves, the lining of the heart (the pericardium), and the aorta. It can be used to detect a heart attack, enlargement or hypertrophy of the heart, infiltration of the heart with an abnormal substance. Weakness of the heart, cardiac tumors, and a variety of other findings can be diagnosed with an echocardiogram.

The TTE is commonly used to help diagnose endocarditis. Diagnostic findings by the Echocardiogram include definitive evidence of vegetation or thrombus on valves or other endocardiac structures, abscesses, or disruption of a prosthetic heart valve.

The TTE is highly accurate for identifying vegetations, but the accuracy can be reduced in up to 20% of adults because of obesity, chronic obstructive pulmonary disease, chest-wall deformities, or otherwise technically difficult patients. Transesophageal echocardiography, if available, may be more accurate than TTE because it excludes the variables previously mentioned and allows closer visualization of common sites for vegetations and other abnormalities. Transesophageal echocardiography also affords better visualization of prosthetic heart valves.

[edit] Transesophageal echocardiogram

Another way to perform an echocardiogram is to insert a specialised scope containing an echocardiography transducer (TEE probe) into the patient's esophagus, and record pictures from there. This is known as a transesophageal echocardiogram, or TEE (TOE in the United Kingdom). The advantages of TEE over TTE are usually clearer images. The transducer is closer to the heart and doesn't have the ribs and lungs to deflect the ultrasound beam. Several structures are better imaged with the TEE, including the aorta, the pulmonary artery, the valves of the heart, and the left and right atria. While TTE can be performed easily and without pain for the patient, TEE may require light sedation and a local anesthetic lubricant for the esophagus. Children are anesthetized. Unlike the TTE, the TEE is considered an invasive procedure.

In some centers, sedation is used to ease the discomfort to the individual. The use of local anesthetic agents and sedation can decrease the gag reflex, making the ultrasound probe easier to pass into the esophagus. The transducer and cable are then coated in a lubricant, placed in the patient’s mouth, and then passed down the patient's throat. The individual is instructed to swallow while the probe is being passed down, to prevent it from going into the trachea. Although the placement of the thumb-wide transducer is uncomfortable, there are very few complaints of gagging from the patient once the transducer is in the correct location.

[edit] See also

• Aortic valve area calculation

[edit] References

[edit] External links

• SeeMyHeart - Patient Information on Echocardiograms (Heart Ultrasounds)
• American Society of Echocardiography
• Stress Test with Echocardiography from Angioplasty.Org
• Echocardiography information from Children's Hospital Heart Center, Seattle.
• Coronary heart disease And echocardiography
• Echocardiography Resources Simple echocardiography tutorials
• Atlas of Echocardiography Echocardiography Database
• E-chocardiography Internet Journal of Cardiac Ultrasound
• Echobasics Basic introduction to echocardiography - German/Spanish English planned for 2007

International Society of Cardiovascular Ultrasound