ECHO Basics 101: Heart Anatomy

The heart is a cone-shaped, hollow, fibromuscular organ located in the middle mediastinum between the lungs and pleurae. The organ is surrounded by pericardium (which appears echogenic in US) that is made up of fibrous tissue and serosal components. Its purpose is to reduce friction with each cardiac movement; allow freedom of movement of the heart; contains the heart within the mediastinum; and acts as a barrier to infection (i.e. endocarditis). The weight of the heart varies in males (280-340g) and in females (230-280g), and can be calculated by multiplying 0.45% and 0.40% of total body weight in males and females, respectively.

The heart is divided into four chambers: right atrium, left atrium, right ventricle, and left ventricle. The two most important valves are the semilunar (AoV, PV), and atrioventricular (MV, TV). The left side of the heart is usually thicker and contains a great deal of pressure than the right side. However, volume pumped by both sides is equal to ensure normal circulation of flow. The right side supplies the pulmonary circulation with a lower oxygen saturation of about 75%, and receives blood from SVC and IVC that enters to the right atrium. The right side of the heart contains the TV which closes during right ventricular systole and contained blood in right ventricle is propelled out of RVOT through the semilunar PV to the lungs or pulmonary circuit. In contrast, the left side of the heart has a systolic pressure of about 120 mmHg with a high oxygen saturation of 95-100%, and receives blood from the lungs through the pulmonary veins that enters in the back of the left atrium. The left side of the heart contains the MV which opens during left atrial systole and closes during ventricular systole, in which blood is propelled out of the LV through the outflow tract and into the AO.

In ECHO, or Transthoracic Exam, a number of specific protocols are induced and the structures can be viewed from various positions and windows. The shots obtained are the following:

1. Left Parasternal Long-Axis View (PLAX or PSLA)
2. Left Parasternal Right Ventricular Inflow View (RVIT)
3. Left Parasternal Right Ventricular Outflow View (RVOT)
4. Parasternal Short-Axis View (SAX or PSSA)
5. Apical Four-Chamber View (A4C)
6. Apical Five-Chamber View (A5C)
7. Apical Two-Chamber View (A2C)
8. Apical Long-Axis View or Apical Three-Chamber View (A3C)
9. Subcostal Four-Chamber View
10. Subcostal Short-Axis View
11. Subsubcostal Inferior Vena Cava View
12. Suprasternal View/Notch