RESIDENCE TIME IN NICHES OF STAGNANT FLOW DETERMINES FIBRIN CLOT FORMATION IN AN ARTERIAL BRANCHING MODEL - DETAILED FLOW-ANALYSIS AND EXPERIMENTAL RESULTS

Deposition of blood components in branching flow has been investigated primarily with regard to platelets. We instead examined thrombin-indu ced fibrin clot formation in separated laminar as well as turbulent br anching flow. The most rapid clot growth and largest clot mass was obt ained at the lowest inflow rate. Increased inflow reduced the clot siz e and turbulence completely prevented clot formation. Examination of c orresponding flow conditions revealed the recirculation zone in lamina r flow to be characterized by two stationary, counterrotating vortices . Niches of stagnant flow, exhibiting long residence times, low wall s hear rates and characterized by convergent flow, were spared between t he bulk flow and these vortices. Here, fibrin clot growth continued ev en when shear rates were increased more than 100-fold. Our results ind icate that, in branching flow, the long residence times and convergent flow characteristic of flow niches rather than shear rate are critica l for fibrin clot formation.