Arterial and venous thrombosis
Thrombosis is a major cause of death. It causes arterial occlusion resulting in myocardial infarction, stroke or ischemia and venous occlusion leading to deep venous thrombosis or pulmonary embolism.
Endothelial injury is the main cause of arterial thrombosis. Thrombi form at sites with underlying arterial wall pathology e.g. arteriosclerosis. Rupture of the arteriosclerotic lesion induces adhesion and activation of platelets and inflammatory cells induce the release of tissue factor (TF). Venous thrombosis is caused mainly by stasis and hypercoagulability.
Several risk factors for venous thrombosis have been identified:
- Acquired risk factors: immobilization, operation, trauma, plaster, pregnancy, smoking, oral contraception, age, and malignancy.
- Genetic risk factors: deficiencies of natural anticoagulants (antithrombin, protein C and protein S deficiency), factor V Leiden and prothrombin 20210A mutation, blood group non-O.
Thrombosis can be caused by
Which of the following statements is true?
Extra info: A very severe hypercalcaemia that could cause a prolonged PT is incompatible with life. Vitamin K reverses the effect of coumarins. Protamine reverses the effect of heparin. FDPs may be increased in thrombotic conditions but are not specific or sensitive enough to be a useful diagnostic tool.
Dilatation of the peripheral arterial blood vessels can be caused by
Extra info: Answers a, b, and c are known to cause vasoconstriction. Nitric oxide is a potent vasodilator…too bad a pharmacological form of this molecule is not possible.