Episode Of Venous Thrombosis Research Articles

Predisposing factors to venous thromboembolism: Can we detect those at risk?

No test of coagulation or platelet function can reliably, selectively and sensitively predict the risk of venous thromboembolism in the majority of patients, even in the high risk groups. On this basis routine, extensive, preoperative blood testing cannot be recommended, but 2 relatively simple tests can be justified. Polycythaemia constitutes an increased risk situation hence doubling the value of a pre-operativc haemoglobin estimation. Partial thromboplastin time (PTTK) is more commonly recommended as a screening test for an unsuspected bleeding tendency, but considerable evidence has accrued recently to suggest that a significant shortening of the PTTK is associated with an increased risk of venous thromboembolism. Shortening of the PTTK is most commonly seen in traumatized patients or patients with renal or malignant disease. Risk assessment of venous thromboembolism is therefore more dependent on clinical assessment and a knowledge of the known predisposing factors. Both the individual patients and the particular procedure to be performed need to be assessed in this light. A full personal and family history is essential a previous episode of venous thrombosis represents a highly significant risk factor. Individuals with unexplained recurrent thromboembolism or a significant family history should be tested for rare abnormalities such as congenital antithrombin III deficiency or a dysfibrinogenaemia. Particular situations which cause an acquired antithrombin III deficiency slate such as recent heparin therapy and liver disease, D.I.C. should be noted. Medical factors such as C.C.F. limb paralysis or immobilization, oestrogen containing therapy. probably represent additive risk factors. At surgery, the age of the patient, the duration of surgery, presence of malignancy and the nature and site of surgery, the expected degree of tissue trauma and duration of post-operati\e immobilization all need to be taken into account. The advent of a relatively safe, easily administered and effective prophylaxis of low dose heparin with or without an antiplatelet agent or dihydrocrgotamine now oblige the individual physician or surgeon to be more highly aware of these risk factors and include such an assessment in his routine procedure.

The Sequelæ of Inferior Vena Caval Interruption

Recurrent pulmonary emboli occurred in 26 of 85 patients (31%) after inferior vena caval interruption to prevent pulmonary emboli. Sequelae following this procedure included early problems associated with bleeding, venous thrombosis, the sequestration syndrome, and death. Late sequelae were recurrent episodes of venous thrombosis, the post-phlebitic syndrome and recurrent emboli. Inferior vena caval interruption is associated with significant continuing disability, and it fails to solve the problem it was designed to prevent.

Phenformin and ethyloestrenol in recurrent venous thrombosis.

Altogether 75 patients, 60 of whom had recurrent idiopathic deep venous thrombosis, 10 recurrent superficial thrombophlebitis and 5 retinal venous thrombosis, were given a combination of 100 mg phenformin and 8 mg ethyloestrenol a day for periods varying between 3 and 48 months (mean 16.2). Initially, all the patients had an abnormally low plasminogen activator content in the walls of superficial veins and/or a decreased capacity to release plasminogen activator from the vein walls on venous occlusion of the arms. The combination elicited a significant increase in the spontaneous fibrinolytic activity and in the local fibrinolytic activity during standardized venous occlusion of the arms (assayed on fibrin plates) after treatment for 3 months (p less than 0.001). These activities then remained normal throughout the observation period. In 65 of the 75 patients studied, the plasminogen activator level in the vein wall (histochemically assayed by the method of Pandolfi) was abnormally low intitially. The level had increased significantly after treatment for 3 months (p less than 0.001). After treatment for 12 months all the patients except 2 were normal. The patients in this material had had 2-20 episodes of venous thrombosis, the most recent 5 years before the institution of treatment, in spite of dicoumarol treatment. During treatment 9 thrombotic episodes occurred; in 5 of these patients the fibrinolytic activity of the vessel wall was not normal at the time of the recurrence. Except in 1 patient, who developed lactic acidosis, the side-effects were not severe.

In-vitro thrombosis and platelet behaviour after operation.

SUMMARYThrombosis and platelet aggregation were studied with the use of a modified Chandler apparatus as an in‐vitro technique. Fifty‐two healthy control subjects and 63 postoperative patients were investigated. There were three episodes of venous thrombosis in the postoperative group.Thrombus size and plasma fibrinogen levels were significantly greater in patients after operation than in control subjects. The plasma fibrinogen level, but not the thrombus size, was directly related to the extent of the operation. In both control and postoperative patients there was a significant correlation between thrombus size and the plasma fibrinogen levels. The total serum cholesterol level did not relate to thrombus size.The plasma thrombus formation time, but not the whole blood thrombus formation time, was significantly shorter in postoperative than in healthy subjects.Spontaneous platelet aggregation was markedly more frequent in postoperative subjects. This greater frequency could not be related to the elevated plasma fibrinogen levels.It was suggested that the findings with the Chandler apparatus might reflect a tendency to abnormal platelet aggregation which exists as a constitutional diathesis in some subjects after an operation.