The heart is the main organ and is responsible for pumping and controlling the flow of oxygen through the body. The rate of contractions is controlled by electrical impulses from the Sino-Atrial Node.The right side of the heart collects deoxygenated blood from two large veins, the superior and inferior vena cavae. The left side of the heart receives oxygenated blood from the pulmonary veins. It is then pumped into the left ventricle through the mitral valve and into the aorta through the aortic valve for systemic circulationDiagnosis of heart disease is often done by the taking of a history, listening to the heart with a stethoscope, ECG, and an ECHO.