Applications in Acquired Heart Disease

There is a direct relationship between the frequency shift, Fd, and the maximum red cell velocity (Vm), as expressed in Equation 1–2: $$ \text{VM} = [\text{cFD}]/[2\text{F}'\text{cos}{\beta}] $$ where c is the acoustic velocity, F’ is the transducer frequency, and s is the angle of incidence between the ultrasonic beam and the blood flow. When obstruction to flow is present, an increase in red cell velocity will occur. By accurately recording the peak transvalvular flow velocity, the pressure gradient existing across the valve can be estimated noninvasively.