Deep Vein Thrombosis: Difference between revisions

Introduction[edit|edit source]

深静脉血栓形成(DVT)是一种血液clot that forms within the deep veins, usually of the leg, but can occur in the veins of the arms and the mesenteric and cerebral veins.

• A common and important disease.
• It is part of the venous thromboembolism disorders which represent the third most common cause of death from cardiovascular disease after heart attacks and stroke.
• Account for most cases of pulmonary embolism. Only through early diagnosis and treatment can the morbidity be reduced^[1].
• Even in patients who do not get pulmonary emboli, recurrent thrombosis and "post-thrombotic syndrome" are a major cause of morbidity.^［2］

Pathophysiology[edit|edit source]

According to Virchow's triad, the following are the main pathophysiological mechanisms involved in DVT:

• Damage to the vessel wall
• Blood flow turbulence
• Hypercoagulability^［2］

DVT is commonest in the lower limb below the knee and starts at low-flow sites, such as the soleal sinuses, behind venous valve pockets.^［2］[3].^[4]

• Clots are firm and are mostly made up of fibrin and red blood cells^[1](see the image of a DVT here). On autopsy, the majority are attached to venous walls.^[1]
• Within 72 hours, an estimated 50% of intraoperative calf DVTs resolve on their own.^[4]
• About 1 in 6 of these extend into the proximal veins of the leg,^[4]causing venous obstruction and damage to affected valves.
• A subset of proximal DVT becomes mobile and progresses topulmonary embolism(PE), a potentially fatal condition.

The following video provides a visual representation of DVT pathology:

Risk Factors[edit|edit source]

Following are the risk factors and are considered as causes of deep venous thrombosis:

• Reduced blood flow: Immobility (bed rest, general anesthesia, operations,stroke, long flights)
• Increased venous pressure: Mechanical compression or functional impairment leading to reduced flow in the veins (neoplasm, pregnancy, stenosis, or congenital anomaly which increases outflow resistance)
• Mechanical injury to the vein: Trauma, surgery, peripherally inserted venous catheters, previous DVT, intravenous drug abuse.
• Increased blood viscosity: Polycythaemia rubra vera, thrombocytosis,dehydration
• Anatomic variations in venous anatomy can contribute to thrombosis.

Increased Risk of Coagulation

• Genetic deficiencies: Anticoagulation proteins C and S, antithrombin III deficiency, factor V Leiden mutation
• Acquired: Cancer,sepsis,myocardial infarction,heart failure, vasculitis,systemic lupus erythematosusand lupus anticoagulant,Inflammatory bowel disease,nephroticsyndrome, burns, oral estrogens,smoking,hypertension,diabetes

Constitutional Factors

• Obesity, pregnancy,Increasing age, surgery, and cancer.

Clinical Presentation[edit|edit source]

History

• Pain (50% of patients)
• Redness
• Swelling (70% of patients)

Physical Examination

• Limb edema may be unilateral or bilateral if the thrombus is extending to pelvic veins
• Red and hot skin, with dilated veins
• Tenderness^［2］

Clinical Prediction Rule (CPR): Well's Criteria[edit|edit source]

好了's Criteria is the most commonly used tool to screen for DVT risk:^[1]

Clinical Variable	Score
Active cancer (treatment ongoing or within previous 6 months, or palliative)	+1
Paralysis, paresis, or recent plaster immobilization of the lower extremities	+1
Recently bedridden for > 3 days or major surgery within 4 weeks	+1
Localized tenderness along the distribution of the deep venous system (Tenderness along the deep venous system is assessed by firm palpation in the center of the posterior calf, the popliteal space, and along the area of the femoral vein in the anterior thigh and groin)	+1
Entire lower extremity swelling	+1
Calf swelling > 3 cm when compared with the asymptomatic lower extremity (measured 10cm below the tibial tuberosity)	+1
Pitting edema confined to the symptomatic lower extremity	+1
Collateral superficial veins (non-varicose)	+1
Alternative diagnosis as likely or greater than that of proximal DVT (More common alternative diagnoses include cellulitis, calf strain, Baker Cyst, or postoperative swelling)	-2

In the original scale, the total score for all items is tallied and the probability of the patient having a DVT is as follows: 0= low probability, 1-2 points= moderate probability,and ≥ 3 points= high probability.^[5]An updated version simplifies the scoring process into two categories: < 2 points= DVT unlikely, ≥ 2 points= DVT likely.^[6]

好了's Criteria is a valid tool for assessing DVT risk in outpatient^[7][8]and trauma^[9]patients. It is less useful for stratifying risk in cancer patients^[8]and hospitalized patients as a whole.^[10]It cannot be used to screen for UE DVT.^[11]

Clinical Tests/Examination[edit|edit source]

The clinical diagnosis of DVT is unreliable. However, in combination with valid screening tools, clinical examination can justify the need for diagnostic testing.

• Focus on identifying the signs and symptoms described in the "Clinical Presentation" section of this article.

Homan's Sign

Diagnostic Procedures[edit|edit source]

As per the NICE guidelines following investigations are done:

• D-dimers (very sensitive but not very specific)
• Coagulation profile
• Proximal leg vein ultrasound, which when positive, indicates that the patient should be treated as having a DVT^［2］

D-Dimer Testing

• D-dimer testing is a simple blood test of fibrin degradation. D-dimer levels are increased by any condition that produces fibrin, one of the primary components of deep vein thrombi. The negative likelihood ratio is higher than 99%. According to Wells and colleagues,^[12]the test is best used to rule out DVT in outpatients with a low probability of proximal DVT.
  

管理/干预[edit|edit source]

Primary Prevention[edit|edit source]

A combination of mechanical and pharmacological measures can be used to prevent DVT. Mechanical prophylaxis involves the use of graduated compression stockings (GCS), intermittent pneumatic compression (IPC) and venous foot pumps to improve blood flow in the deep veins of the leg. Common agents for pharmacological prophylaxis include Warfarin, subcutaneous unfractionated heparin (UFH) and low-molecular-weight heparins (LMWH).^[3]DVT prevention is most effective when both methods are used simultaneously.^[1]In medical and surgical patients ambulation and exercises involving ankle dorsiflexion are encouraged to further minimize venous stasis.^[1]

Medical Treatment[edit|edit source]

Anticoagulation[edit|edit source]

Anticoagulation is the usual treatment for DVT. Patients are generally initiated on a brief course (i.e., less than a week) of heparin treatment.^[13]If heparin is contraindicated, fondaparinux (FDX) or direct oral anticoagulants (DOAC) [ex. Xarelto, dabigatran, apixaban] may be used.^[1]Acute DVT treatment is followed by a maintenance course (typically 3-6 months) of warfarin or other Vitamin K inhibitor.^[1][13]Variations in treatment may exist for patients with delayed removal of an intravenous catheter or an ongoing tumor disease in the case of UE DVT.^[11]

Thrombolysis[edit|edit source]

Although rarely indicated, thrombolytic therapy is used to treat extensive blood clots.^[1]A meta-analysis of randomized controlled trials by the Cochrane Collaboration^[14]shows improved outcomes with thrombolysis, though this benefit comes at the increased risk of serious bleeding complications.

Inferior Vena Cava (IVC) Filter[edit|edit source]

印度河流域文明过滤器s may prevent pulmonary embolisation and is an option for patients with an absolute contraindication to anticoagulant treatment.^[15]Most newer filters can be removed at a later date, if desired.^[1]Complications of this intervention include filter erosion, filter migration and obstruction of the inferior vena cava.^[1]

Secondary Prevention[edit|edit source]

Early Mobilization[edit|edit source]

In conjunction with anti-coagulation, bed rest is commonly prescribed in the immediate days following the diagnosis of LE DVT. This practice is applied with the intent of preventing clot dislodgement and the incidence of PE. The theoretical basis behind this protocol has not been supported by the literature.^[16][17]According to a systematic review,^[17]early ambulation is associated with fewer incidences of new PE and decreased mortality. As such, early mobilization is instrumental for the prevention of DVT sequelae (see the next section on "Implications for Physical Therapy Practice" for guidelines on safe patient mobilization following known DVT).

Graduated Compression Stockings[edit|edit source]

To prevent DVT recurrence, the application of graduated compression stockings is recommended "beginning within 1 month of diagnosis of proximal DVT and continuing for a minimum of 1 year after diagnosis".^[18]

Implications for Physical Therapy Practice[edit|edit source]

Physical therapists work with patients at risk for and with diagnosed DVT across the continuum of care. For this reason, the American Physical Therapy Association (APTA) has developed clinical practice guidelines (CPG)^[19]to facilitate decision making in the prevention and management of LE DVT in adults. The following table outlines the 5 responsibilities of physical therapists (PTs) with actionable recommendations:

PT Responsibilities	Actionable Recommendations
(1) Prevention of VTE	Encourage patient mobility and physical activity at the individual and institutional level. Recommend/use mechanical compression for individuals at moderate or high risk for DVT Consult with the physician about medication for individuals at moderate or high risk for DVT Provide education on DVT prevention (leg exercises, ambulation, hydration, etc) Provide education on the risk factors, signs and symptoms, and consequences of DVT
(2) Screening for LE DVT	Screen for DVT risk using Well's Criteria or the preferred risk assessment model of the treating institution. Communicate screening results and relevant clinical signs and symptoms to the medical team. Provide education on the importance of seeking medical attention for suspected DVT.
(3) Making prudent decisions regarding safe mobility in conjunction with the health care team	Advocate for diagnostic testing and wait the results before mobilizing patients with suspected DVT Screen for fall-risk when a patient is on anticoagulation therapy Engage patients with known DVT in early mobilization. Recommendations for how and when it is safe to mobilize a patient with known DVT depends on patient fall-risk the medical treatment being used: Medical Treatment Safe Mobilization Guidelines Anticoagulation Verify initiation of anticoagulation and type. Determine if therapeutic levels of anticoagulation have been achieved. Mobilize the patient once he/she is in a therapeutic range.* 印度河流域文明过滤器 Verify placement of an IVC filter. Mobilize the patient once he/she is hemodynamically stable.* Out of bed ordered for a patient with no anticoagulation therapy or IVC filter Consult with the medical team regarding mobility vs continued bed rest.
(4) Prevention of long-term consequences of LE DVT	Engage patients with known DVT in safe mobilization (review section 3 of this table for details). Recommend/use mechanical compression. Provide education on the risks and benefits of mobilization following DVT.
(5) Patient education & shared decision making	Patient education should be given throughout the DVT prevention and management process. Patients should have the autonomy to decide if they want to engage in recommended prevention and treatment measures.

*NOTE: Execution of the above recommendations should be done in line with institution-specific policies. Hillegass et al^[19]offer adecision making algorithmthat may be helpful in the absence of or as a reference point for updating health care system protocols)

Differential Diagnosis[edit|edit source]

Below is a non-exhaustive list for the differential diagnosis of calf pain in patients with suspected LE DVT:^[20][21]

• Pyomyositis
• Fibula shaft fracture
• Cellulitis
• RupturedBaker's cyst
• Neurogenic leg pain
• Hematoma
• 破裂的哦illes Tendon
• Soleus muscle strain
• Acute posteriorcompartment syndrome
• Calf muscle cramps

Resources[edit|edit source]

• Role of Physical Therapists in the Management of Individuals at Risk for or Diagnosed With Venous Thromboembolism: Evidence-Based Clinical Practice Guideline

Presentations[edit|edit source]

References[edit|edit source]