DYNAMIC BACK FLOW INDEX
C.Franceschi
Institute of arteriovenous malformations and complex venous insufficiency. Hospital Saint Joseph. 7 Rue Pierre LAROUSSE 75014 Paris France 

In incompetent veins, in two different walking patients; the diastolic back flow volume can be equal as measured in Pstatkis Index, but the rate of back flow can be different. This is due to different level of incompetence and by the way two different degrees of hydrostatic pressure column fractionning ( HPCF) effects of the valvulomuscular pump (VMP).That is to say  that a total or partial incompetence have the same volume of back flow but with different rate of back flow and different effect on the distal pressure, especially if  walking rhythm  is such as backflow time is less than walking period. The testing has to be "physiologic" and reproduce the VMP behaviour. So the Paranà manoeuvre (PM) ( isometric reflex contraction of the lower limbs in stationary standing position)  may be the best way for a Dynamic back flow index (DBFI). DBFI is VmR²/VmS².tR/tS where VmR is the mean of velocity , Vms is the mean of systolic flow velocity, tR is diastolic back flow time and the systolic flow time. Further-more, if in PM,  the back flow diastolic volume/ systolique volume ratio is more than 1, that means the presence of open venous shunt (OVS)  and the value of the ratio could be proportional to the importance of the OVS.