Which of the following is/are true regarding normal peripheral arterial flow waves?

a. Flow is antegrade and rapidly accelerated in early systole

b. There is a rapid deceleration phase during which velocities fall to 0

c. A short period of flow reversal occurs in early diastole

d. Low level forward flow continues throughout the remainder of diastole 

The characteristic triphasic audible Doppler signal represents distinct phases: rapid acceleration in early systole, a sharp peak at maximal velocity, a rapid deceleration phase, a short flow reversal phase in early diastole secondary to elastic recoil and finally low level forward flow throughout the remainder of diastole. Beyond an obstruction the flow pulse becomes more rounded, the acceleration phase is less rapid, the peak less well defined, the reverse flow component disappears, and the velocities remain above baseline throughout diastole.