Introduction - ECG Acquisition and Automated Remote Processing - page 2

from ventricles, unidirectional flow of blood is controlled by two types of valves,
viz. tricuspid valve and mitral valve. There is a thick wall of muscle, named
septum, which separates the right side and the left side of the heart. More details of
human heart physiology can be found at [ 1 , 2 ].
The atria receive the blood from the body, and ventricles supply the blood. The
pair of atria and ventricles work in tandem, i.e., they contract and expand together
to collect and supply blood, respectively. In between these two operations, there is
an important function of purification, which is performed by sending the impure
(deoxygenated) blood to the lungs. To achieve this, the right ventricle sends the
impure blood to the lungs and receives the pure blood at the left atria.
A complete cardiac cycle consists of collection of blood from body organs, its
purification, and sending it back to the whole body. Figures 1.1 and 1.2 describe
the schematic circulatory flow of blood between heart chambers and body organs
for one cycle. Deoxygenated blood from the upper and lower parts of the body is
brought through superior vena cava and inferior vena cava, respectively, to the
right atrium to force fill it. When the pressure inside the right atria reaches a
certain value, the tricuspid valve opens to give the passage for blood to the right
ventricle. When the right ventricle is filled up, the pulmonary valve opens to pump
the blood to the lungs through pulmonary artery. In the lungs, the purification
(oxygenation) of the blood takes place by transfer of O 2 and CO 2 by their dif-
ference of partial pressure between inside and outside of alveolar sacs. The
purified blood is brought back to the left ventricle by pulmonary vein to force fill
it, till the pressure reached a certain value, when the bicuspid valve (also called
mitral valve) opens. The ventricle receives the oxygenated blood and then finally
pumps it to the whole body through the aortic semilunar valve to the aorta. The

Fig. 1.1 Circulatory blood flow through the heart chambers