An echocardiogram is a sonography of the heart. Also known as a cardiac ultrasound, it uses standard ultrasound techniques to image two-dimensional slices of the heart. The latest ultrasound systems now employ 3D real-time imaging.
In addition to creating two-dimensional pictures of the cardiovascular system, an 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 an early 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 (see Doppler echocardiography).
Echocardiography is usually performed by cardiac sonographers and interpreted by a cardiologist.
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. With advanced measurements of the movement of the tissue with time (tissue doppler), it can measure diastolic function, fluid status, and dys-synchrony.
The TTE is highly accurate for identifying vegetations (masses consisting of a mixture of bacteria and blood clots), 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. TTE in adults is also of limited use for the structures at the back of the heart, such as the left atrial appendage. Transesophageal echocardiography 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.
In adults, several structures can be evaluated and imaged better with the TEE, including the aorta, pulmonary artery, valves of the heart, both atria, atrial septum, left atrial appendage, and coronary arteries. While TTE can be performed quickly, easily and without pain to the patient, TEE requires a fasting patient, a team of medical personnel, takes longer to perform, is uncomfortable for the patient and has some risks associated with the procedure (esophageal perforation--1 in 10,000, and adverse reactions to the medication).
Before inserting the probe, conscious sedation is induced with the patient to ease the discomfort of the individual and to decrease the gag reflex, thus making the ultrasound probe easier to pass into the esophagus. Conscious sedation is a light sedation usually using the medications midazolam (a benzodiazepine with sedating, amnesiac qualities) and fentanyl. Sometimes a local anesthetic spray is used for the back of the throat, such a xylocaine and/or a jelly/lubricant anesthetic for the esophagus. Children are anesthetized. Unlike the TTE, the TEE is considered an invasive procedure and is thus performed by physicians in the U.S., not sonographers.
3-D echocardiography is now possible, using an ultrasound probe with an array of transducers and an appropriate processing system. This enables detailed anatomical assessment of cardiac pathology, particularly valvular defects, and cardiomyopathies.. The possibility of slicing the virtual heart in infinite planes in anatomically appropriate manner and reconstruct 3dimensional images of anatomic structures make 3D echocardiography unique for understanding the congenitally malformed heart. (Ref: Impact of Multiplanar Review of Three-Dimensional Echocardiographic Data on Management of Congenital Heart Disease. Ann. Thorac. Surg., September 2008; 86: 875 - 881).
The "Intersocietal Commission for the Accreditation of Echocardiography Laboratories" (ICAEL) sets standards for the echo labs, cardiologists and technologists in the US to comply to. Once all requirements have been met, the lab will receive ICAEL certification. A lab that has received the certification may also receive higher reimbursement from insurance companies such as Medicare and United Healthcare. http://www.icael.org/icael/index.htm
In the UK, accreditation is done by the British Society of Echocardiography. Accredited technologists or other professionals from the echocardiography field will have completed a logbook and passed an exam