Thrombosis is the formation of a blood clot within the vascular system, frequently causing obstruction. There are two forms of thrombosis, venous thrombosis and arterial thrombosis. German physician Rudolf Virchow first postulated, that a triad of conditions predispose to thrombus formation, these three factors being abnormalities in the vessel wall, blood flow and the coagulability of blood. The lesion and the syndrome produced by the thrombus depend on its location and size.
Clinical presentation depends on type of vessel and organ involved and associated embolism. Cases of deep venous thrombosis (DVT) present with swelling of leg, discoloration of leg and pain. Cases of pulmonary embolism often are secondary to deep venous thrombosis and present with acute chest pain, dyspnea, cough, and hemoptysis.
Embolus in internal carotids, vertebral arteries and circle of Willis presents with recurrent dizziness, confusion, limb weakness, sensory dysfunction, speech disorders, facial asymmetry, bladder dysfunction and abnormal gait. Thromboembolic complications in the heart presents with severe chest pain, sweating, palpitation, anxiety and syncope. Portal vein thrombosis may cause adnominal distension, pain in abdomen and breathing difficulty. Jugular vein thrombosis causes fever, neck swelling, and cervical pain .
Objective of workup is confirming obstruction of vessel lumen by imaging studies such as color Doppler for deep venous thrombosis and portal vein thrombosis, angiography in case of myocardial infarction or ischemia, CT scan and X-ray in case of jugular or carotid involvement. ECG, complete blood count (CBC), kidney function test, liver function test, urine examination and blood coagulation profile (PT, aPTT, INR), must be done to rule out complications and set baseline. Depending on complications other investigations like CSF or peritoneal fluid examination may be advised .
Treatment is directed towards two aspects. Treatment of complication and treatment to dissolve as well prevent recurrence of thrombus. Treatment of complication like swelling and pain of leg in DVT are managed by stockings and NSAIDS. Myocardial ischemia/infarction with centrally acting analgesics, nitroglycerine and life support. Pulmonary thromboembolism with oxygen, and other life support, antibiotics.
Whatever is a complication, cornerstone of treatment is dissolving blood clot and prevent recurrence. Thrombolytic drugs like streptokinase or human tissue plasminogen activator are used to dissolve clot. For prevention of thrombus formation anticoagulants like heparin, warfarin, and dabigatran are used. Anticoagulant and thrombolytic therapy needs routine INR monitoring .
Mostly cases are detected upon symptoms or complications. If left untreated thrombosis causes significant morbidity and mortality due to cardiopulmonary complications like pulmonary thromboembolism, stroke or myocardial infarction. Complications are mostly prevented by anticoagulant therapy. Even after treatment in 33 percent of cases, the condition recurs .
Thrombosis occurs as a result of altered pathophysiology between blood flow, protection of vessel wall by endothelium and blood composition. Regular blood flow prevents endothelial injuries and activation of coagulation pathway. This flow is altered in certain conditions like sedentary behavior, prolonged sitting or standing, occlusion of vessels by tumors, atrial or ventricular fibrillation, shock and heart failure .
In the endothelium if injured, connecting tissue containing collagen, is exposed to coagulation factor which activates coagulation pathway. Endothelial injury may be caused by uncontrolled blood pressure, stress, atheroma, infection and altered blood flow.
Hypercoagulability indicates altered composition of blood. It is mostly due to autoimmune conditions like deficiency of antithrombin, protein C or protein S or immunological conditions like antiphospholipid antibody syndrome .
Annually 1 to 2 per thousand new cases are diagnosed in US. Incidence increases with age up to 1 per 100. Out of this 10 to 30 percent of diagnosed cases die within month of diagnosis. In 33 percent cases there is recurrence of condition in next 10 years. 5 to 8 percent of Americans have genetic predisposition for thrombosis. Incidence of thrombosis increases with age, weight, sedentary lifestyle, smoking and stress .
Injury to blood vessel causes exposure to tissue factor or collagen in vessel walls depending on nature of injury. In both cases it activates platelets and forms a platelet plug. Activated platelets along with tissue factor and collagen in vessel wall initiate a cascade of actions known as coagulation pathway which may be intrinsic or extrinsic depending on etiology. This leads to initiation and formation of plug of platelets enmeshed in fibrin thread. This plug if large in size causes diminution of vessel lumen size resulting in either decreasing blood flow if vessel is vein and diminished blood supply to tissues if vessel is artery.
Accordingly thrombosis is classified as arterial or venous. Arterial thrombosis causes decreased blood supply to supplying tissue resulting in ischemia or infarct . Examples are stroke, myocardial infarction and limb ischemia. Venous thrombosis causes stagnant blood flow in backward direction of flow and edema of distal part of body where it is occluded. Examples are jugular vein thrombosis, cerebral venous sinus thrombosis, Budd-Chiari syndrome and Paget-Schroetter disease.
Since many risk factors for thrombosis are modifiable, prevention of thrombosis is possible. This includes weight reduction, exercise, diet control, smoking cessation, stopping hormonal contraceptive and control of blood pressure. Once condition is developed, anticoagulant therapy will be added to this list of factors for prevention of recurrence .
Formation of clot within vessel wall is called thrombosis. Thrombosis cause stagnancy of blood flow within vessels by narrowing the lumen which may precipitate edema if vein is involved or ischemia of tissue if artery is involved. Clot may dislodge from its original position leading to embolism in organ where it is lodged.
Symptoms and sign of thrombosis depend on vessel and organ involved. The condition is often detected after complications such as myocardial infarction, pulmonary embolism, and stroke. Management includes management of complication and thrombolytic therapy. Thrombosis is a preventable condition and could be avoided by diet and weight control, control of blood pressure, regular exercise, change of occupation, early detection and treatment of certain conditions with anticoagulants or antiplatelet drugs.