The echocardiogram is an ultrasound of the heart. Using standard ultrasound techniques, two-dimensional slices of the heart can be imaged. Ultrasonographic imaging of the heart is a noninvasive technique that depends on the differing ability of the structures within the heart to reflect ultrasound waves.
The standard echocardiogram is also known as a trans-thoracic 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.
Another method to perform an echocardiogram is to insert the echocardiography transducer within the patient’s esophagus, and record pictures from there. This is known as transesophageal echo, or TEE. The advantage of TEE over TTE are that better pictures can be produced, since there is less tissue between the transducer and the structures that are being imaged. Also, certain structures of the cardiovascular system are not ammenable to adequate imaging via TTE, including the aorta, the pulmonary artery, the valves of the heart, and the left and right atria. These structures are usually well visualized on trans-esophageal echocardiography.
In addition to creating two-dimensional pictures of the cardiovascular system, the echocardiogram can also produce accurate assessment of the direction of blood flow and the velocity of blood and cardiac tissue at any arbitrary point. 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.
Echocardiography was the first medical application of ultrasound.
M-mode echogardiography: A scan is produced on a paper moving at constant speed to produce a single dimension image.
2-dimensional (real time) echocardiography: A 2-D fan shaped image of a segment of the heart which may be frozen and hard copied. Several views are possible, the commonest being: long axis, short axis, 4-chamber, and subcostal.
Doppler (color flow) ultrasonography: This is good for visualizing blood flow across valves and congenital abnormalities. The blood flow is colorized.
Transesophageal echocardiography: A special device is inserted into the esophagus that enables ultrasonographic visualization of the heart and large vessels. Good for diagnosing aortic dissection, vegetations on heart valves. For a more detailed discussion of transesophageal echo, click here!
Stress echocardiography: Used to evaluate ventricular function, ejection fraction and regional wall motion in response to exercise.
- Diagnosis of heart failure (almost 10 times more accurate than the ECG) and estimation of ventricular heart function.
- Diagnosis of congenital heart disease
- Diagnosis of endocarditis and valve disease
- Diagnosis of pericardial effusions
- Diagnosis of mural thrombus
- Diagnosis of aortic aneurysms
- Diagnosis of cardiomyopathy