Arteriovenous graft: A connection via an artificial vessel, between an artery and a vein. Artificial grafts are typically made of Dacron.
Deep venous thrombosis: A thrombus which forms in the deep veins of the legs. If these dislodge, they can go to your lungs and cause sudden death.
Diastole: The portion of the cardiac cycle when the heart refills with blood.
Fibrinolytic: The property of breaking down fibrin; one of the constituents of a thrombus or blood clot.
Hematocrit: The portion of blood consisting of erythrocytes.
Intima: The inner lining of a blood vessel composed of endothelial cells.
Non-Newtonian fluid: A fluid whose viscosity changes with shear or flow. Think of ketchup. It’s thick, but gets thinner and easier to pour when you shake it.
Organization: The process in which new blood vessels grow into a thrombus or dead tissue, which allows influx of fibroblasts, which produce collagen, the main constituent of a scar.
Reynolds number: The number which describes the propensity of a flowing fluid to deviate from orderly or laminar flow to form eddies when encountering an obstruction. The higher Reynolds number, the more likely is eddy formation. At a high enough Reynolds number, flow is turbulent.
Shear rate: The velocity gradient of parallel fluid layers or the rate at which layers of fluid slide over each other. Calculated as the first derivative of flow velocity with respect to distance from the vessel wall; think of the ratio between blood flow velocity and vessel diameter as shear rate.
Shear stress: Friction that blood flow causes against the inside of arteries or the tangential frictional force per unit area applied by blood flow upon the endothelial wall. It is calculated as shear rate multiplied by blood viscosity.
Stroke volume: The amount of blood expelled during systole.
Systole: The portion of the cardiac cycle when the heart contracts, expelling blood.
Virchow: A famous German pathologist of the 19th century. He postulated Virchow’s triad, three elements which allow formation of a thrombus: stasis of blood, abnormalities of the vessel wall, and hypercoagulability or increased propensity of blood to clot. Small pockets of blood stasis outside of the main flow occur if Reynolds number is sufficient. Decreased blood flow decreases endothelial production of protective molecules, constituting a vessel wall abnormality. Hypercholesterolemia makes blood hypercoagulable by increasing the formation of erythrocyte aggregates and viscosity at low shear.