Disorders of the Veins and Arteries
June 15, 2021
Deep vein thrombosis
Deep vein thrombosis (DVT) – is a pathological state, which is characterized by formation of thrombus inside deep veins, predominantly in the legs. DVT commonly develops in the calf veins and spreads towards the flow of blood. When it does not grow, it can be cleared naturally by fibrinolysis. The factors of Virchow’s triad, such as hypercoagulability (increased tendency to clot), venous stasis (a decreased blood flow rate) and changes in the endothelial blood vessel lining are commonly used to explain the reason of its formation. The beginning of vein thrombosis is caused by thromboplastin, which leads to conversion of prothrombin to thrombin, followed by fibrin deposition (Bovill E., 2011). Fibrin attaches the endothelium of the vein, which normally prevents clotting. Red blood cells together with white blood cells, which are the components of venous thrombi, get stuck in the rough endothelium with fibrin. Such factors as trauma that causes the tissue factor from outside of the vascular system entering the blood , cancer that can grow in and around the vein occlude it, cessation of blood flow during the surgery (venous stasis) contribute to DVT. Another factor that contributes to DVT is immobilization, which is caused by lack of physical activity. Venous blood is pushed towards the heart by contraction of the vein’s muscles, but mainly by the physical activity. In case of immobilization, venous blood stays in the vein, causing the extension of the vein, damaging the vessels, which leads to DVT.
Arterial thrombosis differs from venous thrombosis by the factors, causing it. Arterial thrombosis is the formation of thrombus inside the artery and mainly follows rupture of atheroma. Another reason is atrial fibrillation, which causes the stasis of the blood in atria and easy thrombus formation.
DVT may lead to long-term complications named as post-thrombotic syndrome. Another serious complication of DVT that threatens the life is venous thromboembolism. When the clot detaches from the endothelium and travels to the place, where it occludes the vein or the artery. Pulmonary embolism is the most severe complication, caused by blockage of the main artery of the lung or one of its branches.
Chronic venous insufficiency
Chronic venous insufficiency (CVI) – is a pathological condition in which veins are not able to pump enough oxygen-poor blood back to the heart (Society for Vascular Surgery, 2009). This is caused by the damaged or ‘incompetent’ vessel as a result of deep vein thrombosis. CVI leads to disorganization of the local system of microcirculation. Inflammation and other pathological processes occurring on the endothelium activate the endothelium cells. Activated cells cause the activation of thrombocytes. In case of chronic alteration process, T-lymphocytes and monocytes attach the endothelium and release highly reactive radicals, leading to the destruction of the endothelial wall of vein. The contact between plasma coagulation factors and tissue factor can trigger the intravascular coagulation, which leads to the formation of thrombus and hinders the oxy-poor blood flow.
As it is stated previously, CVI can be caused by thrombosis of the deep veins, but also by another factors. Both CVI and DVT reduce the flow of oxy-poor blood, but due to different reasons. In DVT case, the blood flow is hindered by the thrombus that occludes the vein, whereas in CVI case the blood cannot be pumped due to the vessels disorder commonly, which leads to reverse flow of blood and varicose extension of veins. CVI is the consequence of DVT, but stasis, caused by the damaged vessels may lead to thrombosis, so these processes are connected.
When the person is in the upright position, the blood from leg veins must flow against the gravity. Leg muscles squeeze the deep veins of legs, what is the major part of venous pump. When the muscles relax, the blood is prevented from flowing down by closure of vessels, but due to the flexibility of the veins and continuous sitting, standing for a long time, or immobilization at all, veins can stretch. This may lead to the weakening of the walls of veins and damaging the vein vessels, causing the CVI. Reduced flow and increased pressure may lead to thrombosis of deep veins.
Immobilized patients with the CVI require physical activities in order to pump the static venous blood, but the best treatment of the disease is its prevention. Constant wearing of compression stockings prevents the veins from extension and damage. In case, if the CVI is the complication of DVT, anticoagulants are prescribed. In severe cases of DVT thromboectomy is necessary.