The Effect of Aging on Venous Valves

Abstract

Objective-Age is the strongest risk factor for venous thrombosis. Vessel wall changes such as thickening of venous valves may be one of the contributing mechanisms. We determined thickness and function of venous valves in the popliteal vein with ultrasound in 77 healthy individuals. Methods and Results-The study included 6 age groups ranging from 20 to 80 years old. Thickness of the valves was compared between age groups. Valve closure time was assessed as an indicator for valve function. In 69 of 77 participants, valve parameters could be measured. We found an increasing thickness of the valves with age, with a mean thickness of 0. Key Words: aging Ⅲ ultrasonic diagnosis Ⅲ venous thrombosis Ⅲ venous valves D eep-vein thrombosis (DVT) of the lower extremities is a disease with an annual incidence of 1 to 2 per 1000. 1,2 Risk factors for venous thrombosis can be divided into acquired and genetic risk factors. Among genetic risk factors are deficiencies of antithrombin, protein C, and protein S, which give a high risk for DVT but have low societal impact because of their low prevalence (Ͻ0.1%). 3 Risk factors such as the prothrombin 20210A and Factor V Leiden mutations are highly prevalent (3% to 8%) and are of intermediate strength. 4,5 Surgery and use of oral contraceptives are examples of highly prevalent acquired risk factors.Aging is the strongest risk factor for venous thrombosis. In people under the age of 40, the incidence is less than 1 per 10 000. 6 However, the incidence of venous thrombosis increases to 1 per 100 per year in elderly over the age of 75. 7 It is not clear why age is such an important risk factor. Explanations such as a decrease in mobility, an increase in prevalence of diseases with a high thrombotic risk (ie, malignancies, hip fractures), reduced venous compliance in the calf, and damaged venous valves have been suggested. 8 -10 Venous valves function to ensure that a proper inflow of blood reaches the heart during various cardiovascular adjustments. They can be regarded as flow modifiers that act and react constantly. 11,12 Venous valves are bicuspid and are positioned in a valve sinus, which is a local widening of the venous wall. The area between a valve leaflet and the vessel wall is called the valve pocket and is regarded as the place where thrombi originate. Low shear stress areas and stasis of blood flow predispose to thrombus formation. In the deepest part of the valve pockets, fluid circulates with very low velocities, creating a low shear field, thus allowing red cells to aggregate. Stagnation of blood leads to hypoxia, which subsequently causes endothelial damage. In case of nonpulsatile flow, a canine study showed that a thrombus was formed on a valve cusp after only 2 hours. 13 Age-related changes of the venous wall and valves have been described in renal veins. 14 Muscle fibers in the vessel wall atrophy with increasing age, whereas elastic fiber bundles hypertrophy. With respect to the valves, a gradual thickening with age was seen as a result of an increased number of ...

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