Deep venous thrombosis . why it happens and what are the risks of the blood clot
Dr. Ebraheim’s educational animated video describes the conditions of Deep Venous Thrombosis (DVT) and Pulmonary Embolism (PE).
What is deep vein thrombosis (DVT)? DVT is the formation of a blood clot (thrombus) within a deep vein. The deep veins pass through the deep tissues and the muscles. Muscle contractions (walking, running, activity, etc.) squeeze blood through the deep veins to the heart. The deep veins have valves which prevent the blood from flowing back to the ankles and feet. When a blood clot is formed, the majority of blood clots are small and they are usually broken down or dissolved. Large clots may form and can block the vein causing the patient to complain of pain and swelling. Homan’s sign is not very specific. High index of suspicion is necessary for the diagnosis.
Virchow’s Triad contributes to the development of dep venous thrombosis.
There are several risk factors for DVT:
•The most important risk factor for DVT is history of previous DVT
•Tumor (malignancy) - up to 20%
•Oral contraceptive therapy
•Aging
•Obesity
•Smoking
•The Virchow’s Triad:
o Venous Stasis
•Intimal injury
o Due to trauma, fracture dislocation or can result from surgery
o Surgery itself is a risk factor because of the use of general anesthesia and the stress due to the surgery.
•Hypercoagulable state
o Could be inherited genetics
o Factor V leiden
o Protein S deficiency
o Protein C deficiency
•Increased blood viscosity + immobilization + an intimal tear from trauma or surgery may lead to DVT.
Once the condition is suspected, venous Doppler ultrasound examination is ordered to confirm the diagnosis. If the study is positive and the clot is above the knee, then the DVT is usually treated with IV heparin therapy followed by long term Coumadin therapy. Occasionally a vena cava filter is used.
Where does deep vein thrombosis (DVT) come from? Deep venous thrombosis (DVT) predominantly occurs within the deep veins of the legs above the knee. It may also occur in the upper extremities.
What conditions can cause DVT?
•Spinal cord injury
•Total knee replacement
o More DVT, less PE than total hip replacement
•Polytrauma patients
•Hip fractures
•Total hip replacement
o Will see less DVT and more PE than total knee replacement surgery
Prophylaxis for DVT (Chemical/Mechanical Prophylaxis
•Chemical methods will include anticoagulants such as aspirin, Lovenox, Coumadin, Heparin and others
•Each of these has their advantages and disadvantages
•Lovenox decreases the incidence of DVT, but does not decrease the rate of death from PE.
•None of the anticoagulation agents including Lovenox provide absolute protection against deep venous thrombosis or pulmonary embolism.
•Both the chest surgeons and orthopaedic surgeons organizational guidelines are related to total joint arthroplasty and hip fractures.
•Currently there are no guidelines for prophylaxis in trauma patients.
•When giving prophylaxis, you weigh the risk of complication such as bleeding versus the benefit of preventing DVT.
•Mechanical prophylaxis should be used more often in the majority of patients or in all patients who need prophylaxis.
•Mechanical compression increases the venous return and the endothelial-derived fibrinolysis.
What is a pulmonary embolism?
A pulmonary embolism is blockage of the pulmonary arteries in the lungs that can lead to death. Usually the pulmonary embolus can become lodged within the upper or lower portion of either one of the lungs. It is possible for the blood clot to become lodged in the middle where the pulmonary artery branches. The incidence of pulmonary embolism occurs in about 700,000 patients per year. Early diagnosis and treatment are the most important factors for survival of the patient. According to the AAOS, the rate of DVT does not correlate with PE. DVT and PE can develop independently of each other and they are a part of the hypercoagulable state. One does not need to have a DVT in order to develop a PE. The origin of PE is debatable. One opinion is that when a blood clot breaks off, it may travel to the heart. If a blood clot becomes lodged in the pulmonary arteries of the lung, this may be fatal. A blood clot may occur in the pulmonary artery itself, not originating from the leg.
Pulmonary embolism should be suspected in patients postoperatively with:
• Acute chest pain
• Tachypnea
• Tachycardia
• Syncope
• Seizures
Diagnosis is done with ventilation-perfusion (VQ) scan and helical chest CT scan. Treatment is done with IV heparin followed by Coumadin. Occasionally a vena cava filter is used.
special thanks for NATHAN ELKINS FOR HIS CONTRIBUTION TO THIS VIDEO