Deep Vein Thrombosis
Deep Venous Thrombosis Veins are thin walled blood vessels that return de-oxygenated blood back to the heart. They are low pressure systems with one way valves within them. Veins may develop clots resulting in deep venous thrombosis (DVT). It is thought that clots develop due to alterations in the blood flow, injury to the vein wall or constituents within the blood that make it prone to clotting. It is often an interplay between these variables however, in the majority of cases, no identifiable cause is found.
What are the risk factors in developing Deep Vein Thrombosis?
There are well established risk factor for Deep Vein Thrombosis. These are listed below. However, there is often a convergence of multiple genetic and acquired risk factors.
- Surgery. Particularly orthopaedic surgery, neurosurgery and general surgery
- Hypercoagulable states. Eg. Factor V Leiden, AT, C and S deficiency, Prothrombin 20210A, Increased factor VIII, Antiphospholipid antibodies
- Previous history of DVT
- Oral Contraceptives
- Oestrogen replacement
- Pregnancy and peripartum
How do we manage DVT?
When there is clinical suggestion of DVT, an ultrasound of the relevant veins is performed. This will confirm the presence of the the DVT. Depending on the site and extent of the DVT, further imaging may be performed eg. MR or CT Venogram.
Once the DVT is confirmed and extent defined, anticoagulation is commenced unless there is contraindications. Standard anticoagulation therapy is intravenous heparin or subcutaneous clexane with commencement of warfarin. This dual regime continues until warfarin is therapeutic. The duration of anticoagulation therapy depends on whether this is the first presentation or recurrent presentation and are there associated risk factors and have they resolved or are ongoing.
If there is a significant risk of PE and anticoagulation is contraindicated or not effective, an Inferior Vena Caval (IVC) filter is considered.
In certain situations, acute thrombolysis is recommended. This is particularly in those young, active patients who present early to hospital with significant DVT in their proximal veins. This is a procedure that aims to resolve the clot with chemical and/or mechanical methods and then address any underlying problem.
Complications of Acute DVT
Recurrent Thromboembolic Events
Recurrent events are common. DVT occurring in conjunction with a major reversible risk factor has a low risk of recurrence once that risk factor is resolved. This is approximately 10% over 5 years. Patients who have no known risk factor ie. idiopathic DVT, are at higher risk of recurrent disease, approximately 30% over 5 years.
Pulmonary Embolism (PE)
PE occurs in approximately 10% of cases and is the most important acute complication of DVT. PE is the third leading cause of cardiovascular death behind heart attack and stroke.
This is the most important late complication of DVT. As a result of the clot within the vein, there is ongoing obstruction to the return of blood as well as the potential for the valves within the veins to be damaged. This may lead to increased pressure in the venous system that results in skin changes and even ulceration.