Preface
Lower extremity deep vein thrombosis is a major factor in pulmonary embolism. Pulmonary embolism is the third leading cause of death in hospitalized patients, second only to cardiovascular and cerebrovascular accidents.
The dangers of lower extremity deep vein thrombosis, in addition to pulmonary embolism, are
(1)bruising of the femur;
(2) sequelae of venous thrombosis.
The prognosis of lower extremity deep vein thrombosis depends on: early diagnosis and standardized treatment.
At present, the following problems exist in the treatment of lower extremity DVT in China.
(1)There are many misdiagnosis, omission and late diagnosis;
(2) Lack of standardized and unified treatment methods;
(3) Coexistence of rough medical treatment and excessive medical treatment.
This specification is based on the internationally recognized ACCP guideline recommendations, combined with more than 20 years of clinical experience and technology of Dr. Zhang Qiang’s vascular team.
Early diagnosis
The early stage of lower extremity deep vein thrombosis can have no symptoms such as swelling. Only when the thrombus spreads and blocks the opening of the collateral veins or spreads rapidly, it shows symptoms such as swelling and pain in the lower extremity. Therefore, most of the clinically diagnosed DVTs are often more than a few days old.
Squeezing the calf muscle, or dorsiflexion of the foot to stretch the muscle can induce calf muscle pain (Homan’s sign), which can indicate early gastrocnemius thrombosis. This test should be a mandatory procedure for physician visits in thrombosis-related departments.
Once a DVT is suspected, aim to perform a lower extremity DVT ultrasound and blood D-dimer test at the first opportunity (within a few hours).
The value of early diagnosis is that early treatment can be initiated. The earlier the treatment, the better the outcome.
Significance of blood D-dimer testing
Plasma D-dimer assay is a test to understand the function of secondary fibrinolysis.
The indicator is elevated in acute deep vein thrombosis and pulmonary embolism. Reminder: The indicator is not elevated in old venous thrombosis.
Indicators can be elevated in other cases: during thrombolysis, myocardial infarction, cerebral infarction, severe hepatitis, surgery, tumors, kidney disease, organ transplant rejection, infection and tissue necrosis.
Therefore, an elevated D2-dimer indicator is not a complete diagnosis of venous thrombosis, whereas a negative indicator can exclude acute venous thrombosis.
Again, a special reminder: once acute venous thrombosis is suspected, plasma D-dimer determination must be done at the first opportunity!
Ultrasonography
Ultrasound has replaced phlebography internationally as the most common screening tool for lower extremity DVT.
Acute venous thrombosis cannot be directly determined on ultrasound images in the early stages. Indirect methods are used clinically to diagnose.
(1) Abnormal dilatation of the deep veins;
(2) incomplete deflation after probe compression;
(3) Loss of deep venous blood flow signal;
(4) Ultrasound cannot clearly determine the thrombosis of the inferior vena cava or iliac vein due to the interference of intestinal gas. Therefore, for patients with high clinical suspicion and normal venous ultrasound findings, CT venography (preferred) or endovenous angiography of the deep veins of the lower extremities is recommended.
For the diagnosis of gastrocnemius vein thrombosis in the lower leg, a high standard of ultrasound equipment and careful examination by a highly qualified physician are required, otherwise the diagnosis is easily missed.
For patients with clinically suspected thrombosis, venous ultrasound should be performed immediately and no appointment should be queued to avoid delays.
Venography
Lower extremity deep venography should not be the first or routine test for patients with lower extremity deep vein thrombosis.
Compared to ultrasound, lower extremity DVT has the following possible drawbacks and risks.
(1) High price ;
(2) Long operation time;
(3) It is not readily available;
(4) Inability to move to the bedside;
(5) Nephrotoxicity of the contrast agent;
(6) Allergic reaction to the contrast medium;
(7) Thrombogenicity of contrast media;
(8) Vascular puncture injury;
(9) Radiation injury;
(10) Artifacts due to contrast retention effects.
Venography is recommended only in the following cases.
(1) CT equipment failure and suspected iliac vein thrombosis;
(2) Before interventional procedures;
(3) in cases where both ultrasound and CT are inconclusive and there is a high clinical suspicion.
It is forbidden to perform unnecessary lower extremity deep venography on patients for research purposes.
CT venography
can be used as the diagnostic method of choice to understand inferior vena cava, iliac vein thrombosis, and iliac vein compression (Cockett syndrome).
Before doing CT, it is important to know whether the patient has suspicious manifestations of inferior vena cava or iliac vein thrombosis: (1) swelling of both lower extremities; (2) angry superficial veins in the abdominal wall.
The recommended equipment is 64-row and above spiral CT.
The scope of the examination should include the level of the renal vein opening.
It must be performed by a physician with experience in CT venography to avoid invalid findings.
CT venography is also associated with possible risks of contrast and X-rays.
Initiate treatment
Once the diagnosis is clear, routine blood tests and coagulation kits are first performed on an emergency basis.
If no contraindication to anticoagulation exists, anticoagulant medication (preferably low molecular heparin subcutaneously) is administered as soon as possible. Warfarin can be administered orally at the same time. When Warfarin is effective and stable (INR index reaches 2.0-3.0 range), discontinue heparin. Warfarin should be continued orally for 3-6 months.
For very early iliofemoral vein thrombosis, cannulation thrombolysis is recommended, provided that the risk of bleeding is assessed.
Anticoagulation therapy
Anticoagulation should be the most common treatment of choice for lower extremity deep vein thrombosis.
The main anticoagulant drugs include.
(1) low molecular heparin.
(2) Warfarin.
Aspirin is an antiplatelet drug, mainly used for arterial thrombosis, and is not effective for acute venous thrombosis.
The principle of anticoagulation therapy: first use low-molecular heparin (subcutaneous injection) for rapid anticoagulation to prevent the spread of thrombosis. Wait for warfarin to take effect and stabilize before discontinuing low-molecular heparin injections.
New anti-Xa oral anticoagulants (e.g. rivaroxaban) are used in the treatment of deep vein thrombosis, which are currently only weakly recommended by ACCP guidelines at present and are more expensive.
Key points of standardized anticoagulation therapy.
(1) Subcutaneous injection of low-molecular heparin precedes oral administration of warfarin. Warfarin has a slow onset of action and can induce thrombosis early in the course of the drug. Therefore, it is important to use low-molecular heparin as the initiating anticoagulation regimen.
(2) Wait for warfarin to take effect and become relatively stable before discontinuing subcutaneous injection of low-molecular heparin.
(3) Adjust the dose of warfarin with reference to the INR index, and maintain the TNR at 2.0~3.0 as the best.
(4) The duration of anticoagulation therapy is in the range of 3-6 months.
(5) Review INR on the third day after each dose adjustment. dose adjustment should be 1/4 tablet each time to avoid large reduction and increase.
(6) There are many factors affecting warfarin and individual differences, try to check INR at least every two weeks.
(7) Do not change the brand of warfarin easily. Because the efficacy of each product is different.
Check the platelets after using heparin to prevent heparin-induced thrombocytopenia (also known as HIT).
For patients with DVT combined with cancer, low-molecular heparin therapy is preferred for at least 3 months of treatment.
Thrombolytic therapy
The word “thrombolysis” refers more to the mechanism of the drug than to the inevitable outcome of the treatment.
It is often more than 48 hours from the formation of venous thrombosis to the appearance of clinical manifestations such as significant swelling of the lower extremities. Therefore, some of the thrombi that begin to mechanize are not sensitive to thrombolytic drugs.
The risk of bleeding with thrombolytic drugs is high, especially in elderly patients with potentially fatal cerebral hemorrhage; placement of thrombolysis reduces the risk of bleeding.
Thrombolytic therapy is not superior to anticoagulation.
Thrombolytic therapy is preferred to local placement thrombolysis, and systemic application increases the risk of hemorrhage.
Further experience is still underway to determine whether the development of cannulated thrombolysis can reduce complications and improve treatment outcomes. From the current clinical results, it is still optimistic, but the indications should be strictly controlled, and the benefit is greater for patients with high-grade thrombosis.
For acute iliac vein thrombosis or inferior vena cava thrombosis, aggressive interventional thrombolysis can be considered if the onset is within one week and no risk factors for bleeding are present.
Malignancy and acute deep vein thrombosis
Lower extremity deep vein thrombosis can be the first clinical manifestation in some patients with malignancy. Therefore, patients with DVT should be routinely screened for tumors and asked for tumor-related medical history.
Patients with malignant tumors are at risk for lower extremity DVT.
The characteristics of patients with malignancy complicated by DVT: hypercoagulable state and bleeding risk coexist.
The preferred treatment for malignancy complicated by DVT is low molecular heparin subcutaneously for more than three months. If survival is expected to be more than one year and there is a risk of anticoagulation, implantation of a vena cava filter is recommended to prevent pulmonary embolism. The permanent type of filter is preferred.
Complicated deep vein thrombosis in pregnant women
With standard treatment, the prognosis is mostly good. It is important to minimize anxiety and depression in pregnant women.
Subcutaneous injection of low molecular heparin is the treatment of choice. Use continues until 6 weeks postpartum.
Discontinue 24 hours earlier in case of cesarean section, epidural placement for anesthesia or induction of labor. Low-molecular heparin can be restarted as soon as 4 hours after cesarean section.
Warfarin use during pregnancy is prohibited.
Deep vein thrombosis during lactation
Neither low molecular heparin nor warfarin is secreted through breast milk and can be used normally.
It is not necessary to discontinue breastfeeding during anticoagulation.
Vena cava filters
A vena cava filter must be implanted in the following cases
(1) if anticoagulation is contraindicated;
(2) in cases of embolic events despite standard anticoagulation;
(3)Termination of anticoagulation due to hemorrhage in the course of standard anticoagulation.
Vena cava filter implantation may be considered in the following cases, as appropriate.
(1) In conjunction with acute deep vein thrombectomy or thrombolysis;
(2) Patients with malignancy who are expected to survive more than 2 years;
(3) floating thrombus in the iliac vein;
(4) Continued spread of thrombus in the anticoagulated state.
(5) Patients at high risk of falls or collisions.
(6) Patient lacks nursing care or monitoring of INR conditions.
If the risk of thrombosis is not persistent, a retrievable filter is recommended.
If there is thrombus spread, or if there is significant thrombus under the filter, and the safety of removal is difficult to guarantee, consider leaving the filter in the body without removing it.
If there is a greater risk of recurrence of thrombosis, or if the patient is older or in poor general condition, a permanent filter should be considered first.
In addition to the above indications for temporary filter implantation, there are: severe polytrauma.
Possible complications of filter implantation include.
(1) Complications associated with puncture of the femoral vein on the healthy side, such as hematoma and thrombosis;
(2) accidental injury to arteries, nerves, etc.;
(3) Complications caused by contrast agents, such as allergy and phlebitis;
(4) Complications when releasing the filter incorrectly, such as filter inversion, filter displacement, filter misalignment, etc;
(5) Other rare complications include vena cava perforation, filter blockage of pulmonary artery, etc.
Routine use of filters for pulmonary embolism prophylaxis is prohibited.
The filter placement procedure must be performed by experienced surgeons.
In critically ill patients, those with contrast allergy, and those with renal insufficiency, conventional filter insertion should be avoided and ultrasound-guided trans-saphenous vena cava filter insertion should be chosen.