A. Echocardiographic Window
Because sound travels poorly through a gaseous medium, it is impossible for ultrasound to traverse the voluminous lung tissue and still obtain adequate echoes from the heart. The transducer must also not be placed over the sternum or ribs or other bony points. Almost all ultrasonic energy is reflected if one tries to direct an ultrasonic beam through bone. Because of the rib cage and breast bone, the best echocardiographic window lies between the second and fifth intercostal spaces and 3–4 cm to the left of the left sternal border.
B. Transthoracic Echocardiogram
The standard transthoracic echocardiogram provides views of the heart with the transducer position on the left chest wall. It gives an adequate visualization of the structures of the heart and abnormalities in more than 95% of patients with valvular heart disease, heart attacks, ischemic heart disease, heart failure, cardiomyopathy, hypertensive heart disease, and assessment of left ventricular hypertrophy. It is, however, not satisfactory for complicated problems in which a transesophageal echocardiogram (TEE) is required.
C. Transesophageal Echocardiogram
TEE is superior to transthoracic echocardiography because the transducer is placed in the esophagus. The esophagus lies immediately behind and adjacent to the left atrium and the thoracic aorta. Specific indications for TEE include congenital heart disease, detection of thrombi in the left atrium, vegetations on the heart valves that occur in infective endocarditis, and for the evaluation of prosthetic heart valves in these situations.

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