title: On the existence of helical flow in veins of the lower extremities.
abstract: OBJECTIVE
  Helical flow has been shown to be present in the heart and arteries, but its existence in veins has not been demonstrated before. This study aimed to investigate if helical flow is present in the venous system and if the venous valves contribute to development of this flow pattern.
  
  
  METHODS
  Color and spectral Doppler were used to calculate the true velocity vectors at five cross-sectional planes of the femoral and common femoral veins in 10 healthy individuals and eight patients with chronic venous disease.
  
  
  RESULTS
  This study demonstrated that helical flow is a normal finding in the segments of veins that are in close proximity and downstream from a venous valve and a venous junction. This flow pattern is more prevalent when the calf muscle pump is active. Incompetence of the proximal great saphenous vein affects the outflow pattern, so that the helical flow is no longer present and is replaced by disorganized turbulent flow.
  
  
  CONCLUSIONS
  These findings suggest that helical flow is detectable, may have a physiological role in venous circulation, and the absence of it may be a feature of venous disease.
authors.affiliation: John A. Burns School of Medicine, University of Hawaii; and Kistner Vein Clinic, Honolulu, Hawaii. Electronic address: flurie@hawaii.edu.
authors.forename: Fedor
authors.initials: F
authors.lastname: Lurie
authors.affiliation: John A. Burns School of Medicine, University of Hawaii; and Kistner Vein Clinic, Honolulu, Hawaii.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Kistner