The study of blood flow at the level of the mitral, aortic and tricuspid valves is usually carried out with the upper apices, and the flow at the pulmonary trunk is carried out along the short axis at the level of the aorta. It is important that the beam was directed strictly parallel to the blood flow.
Normally, the diastolic transmission stream has a two-phase character and is located above the basal line of the spectrogram (since the flow is directed to the sensor). The first phase (peak E) characterizes the movement of blood in the fast filling phase, the second (peak A) – in the atrial systole. The flow through the tricuspid valve has the same shape.
The systolic blood flow through the aortic valve normally has a triangular shape and is represented by one peak, directed below the spectrogram baseline (the flow is directed from the sensor) (Figure 1.13). Flow on the pulmonary valve of the same nature.
Using the scale on the screen, we estimate the velocity of these flows, the pressure gradient on the valve (the pressure difference between the cavities) and some other characteristics. Using special formulas (they are included in the program of the device), it is possible to calculate the orifice area of the corresponding valves. Normally, the flow rate at the valve level usually does not exceed 1.5 meters per second, which roughly corresponds to a pressure gradient of no more than 8–10 mm Hg. All streams are laminar in nature with a clearly defined narrow band spectrum and the presence of a “window” between the points with maximum and minimum intensity.
In the case of color Doppler examination (CDS), blood flows to the sensor are colored red, and from the sensor – blue. The intensity of coloring depends on the flow rate, and in the presence of turbulent flows, additional colors (yellow, green, etc.) are added to the primary colors.