Deep Vein Thrombosis (DVT)

Article Author:
Sheikh Waheed
Article Editor:
David Hotwagner
Updated:
9/6/2018 8:07:13 AM
PubMed Link:
Deep Vein Thrombosis (DVT)

Introduction

A deep-vein thrombosis (DVT) is a blood 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. Deep-vein thrombosis is 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. Even in patients who do not get pulmonary emboli, recurrent thrombosis and "post-thrombotic syndrome" are a major cause of morbidity.[1][2][3]

Etiology

Risk Factors

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-haul 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

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 erythematosus and lupus anticoagulant, Inflammatory bowel disease, nephrotic syndrome, burns, oral estrogens, smoking, hypertension, diabetes

Constitutional Factors

Obesity, pregnancy, Increasing age [4][5][6]

Epidemiology

Incidence and prevalence: Deep-vein thrombosis and pulmonary emboli are common and often "silent" and thus go undiagnosed or are only picked up at autopsy. Therefore their incidence and prevalence are often underestimated. It is thought the annual incidence of DVT is 80 cases per 100,000 with a prevalence of lower limb DVT of 1 case per 1000 population. Annually in the United States, more than 200,000 people develop venous thrombosis; of those, 50,000 cases are complicated by pulmonary embolism.[7][8][9]

Age: Deep-vein thrombosis is rare in children and the risk increases with age, most occurring in the over 40s.  

Gender: There is no consensus about whether there is a sexual bias in the incidence of DVT.   

Ethnicity: There is evidence from the USA that there is an increased incidence of DVT and an increased risk of complications in African Americans and white people when compared to Hispanics and Asians.   

Associated diseases: In the hospital, the most commonly associated conditions are a malignancy, congestive heart failure, obstructive airways disease and patients undergoing surgery.

Pathophysiology

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

  • Damage to the vessel wall
  • Blood flow turbulence
  • Hypercoagulability

Thrombosis is a protective mechanism which prevents loss of blood and seals off damaged blood vessels. Fibrinolysis counteracts or stabilizes the thrombosis. The triggers of venous thrombosis are frequently multifactorial, with the different parts of the triad of Virchow contributing in varying degrees in each patient, but all result in early thrombus interaction with the endothelium. This then stimulates local cytokine production and causes leukocyte adhesion to the endothelium, both of which promote venous thrombosis. Depending on the relative balance between the coagulation and thrombolytic pathways, thrombus propagation occurs. 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. [10][11][12]

History and Physical

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
  • Pain on dorsiflexion of the foot (the Homans sign) 

Evaluation

As per the NICE guidelines following investigations are done:

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

Deciding how to investigate is determined by the risk of DVT. The first step is to assess the clinical probability of a DVT using the Wells scoring system.

  • For patients with a score of 0 to 1, the clinical probability is low, but for those with 2 or above the clinical probability is high.
  • If a patient scores 2 or above, either a proximal leg vein ultrasound scan should be done within 4 hours, and if the result is negative, a D-dimer test should be done. If imaging is not possible within 4 hours, a D-dimer test should be undertaken, and an interim 24-hour dose of a parenteral anticoagulant should be given. A proximal leg vein ultrasound scan should be carried out within 24 hours of being requested.
  • In the case of a positive D-dimer test and a negative proximal leg vein ultrasound scan, the proximal leg vein ultrasound scan should be repeated 6 to 8 days later for all patients.
  • If the patient does not score 2 on the DVT Wells score, but the D-dimer test is positive, the patient should have a proximal leg vein ultrasound scan within 4 hours, or if this is not possible, the patient should receive an interim 24-hour dose of a parenteral anticoagulant. A proximal leg vein ultrasound scan should then be carried out within 24 hours of being requested.
  • In all patients diagnosed with DVT, treat as if there is a positive, proximal leg vein ultrasound scan.[13][14][15]

Treatment / Management

Treatment of DVT aims to prevent pulmonary embolism, reduce morbidity, and prevent or minimize the risk of developing the post-thrombotic syndrome.

The cornerstone of treatment is anticoagulation. NICE guidelines only recommend treating proximal DVT (not distal) and those with pulmonary emboli. In each patient, the risks of anticoagulation need to be weighed against the benefits.[16][17][18]

  • Anticoagulation
  1. Low-molecular-weight heparin or fondaparinux for 5 days or until INR is greater than 2 for 24 hours (unfractionated heparin for patients with renal failure and increased risk of bleeding)
  2. Vitamin K analogs for 3 months
  3. In patients with cancer, consider anticoagulation for 6 months with low-molecular-weight heparin
  4. In patients with unprovoked DVT consider vitamin K analogs beyond 3 months
  5. Rivaroxaban is an oral factor Xa inhibitor which has recently been approved by the FDA and NICE and is attractive because there is no need for regular INR monitoring
  • Thrombolysis: Following are the indications for the use of thrombolytics:
  1. Symptomatic iliofemoral DVT
  2. Symptoms of less than 14 days duration   
  3. Good functional status
  4. Life expectancy of 1 year or more 
  5. Low risk of bleeding
  • Compression hosiery: Below-knee graduated compression stockings with an ankle pressure greater than 23 mm Hg for 2 years (if there are no contraindications)
  • Inferior vena cava filters: If anticoagulation is contraindicated or if emboli are occurring despite adequate anticoagulation

Differential Diagnosis

Following are differential diagnoses of deep venous thrombosis:

  • Cellulitis
  • Post-thrombotic syndrome (especially venous eczema and lipodermatosclerosis)
  • Ruptured Baker’s cyst
  • Trauma
  • Superficial thrombophlebitis
  • Peripheral edema, heart failure, cirrhosis, nephrotic syndrome
  • Venous or lymphatic obstruction
  • Arteriovenous fistula and congenital vascular abnormalities
  • Vasculitis

Staging

The severity of the disease is classified as

  • Provoked: Due to acquired states (surgery, oral contraceptives, trauma, immobility, obesity, cancer)
  • Unprovoked: Due to idiopathic or endogenous reasons; more likely to suffer recurrence if anticoagulation is discontinued
  • Proximal: Above the knee; affecting the femoral or iliofemoral veins; much more likely to lead to complications such as pulmonary emboli
  • Distal: Below the knee

Prognosis

Many DVTs will resolve with no complications.

Post-thrombotic syndrome occurs in 43% 2 years post-DVT (30% mild, 10% moderate, and severe in 3%).

Risk of recurrence of DVT is high (up to 25%).

Death occurs in approximately 6% of DVT cases and 12% of pulmonary embolism cases within one month of diagnosis.

Early mortality after venous thromboembolism is strongly associated with the presentation as pulmonary embolism, advanced age, cancer and underlying cardiovascular disease.

Complications

The following are the two major complications of DVT;

  • Pulmonary emboli (paradoxical emboli if an atrioseptal defect is present)
  • Post-thrombotic syndrome
  • Bleeding from use of anticoagulants

Deterrence and Patient Education

  • Ambulation
  • Wear compression stockings
  • Discontinue smoking

Enhancing Healthcare Team Outcomes

DVTs occur in many hospitalized patients, and one of the most feared complications is a pulmonary embolus. DVTs also result in longer admission to the hospital and drug treatment that can last 3-9 months- all of which adds to the cost of healthcare. Thus, today, the focus is on the prevention of DVT. Besides physicians, both nurses and pharmacists are vital in educating patients about DVT prophylaxis. In fact, nurses are the first professionals to encounter patients being admitted to the hospital and it is here that prevention of DVT starts. Nurses need to educate the patients on the importance of ambulation, being compliant with compression stockings, and prescribed anticoagulation medications. In both the operating room and post surgery, nurses play a key role in reminding physicians for the need of DVT prophylaxis. Each hospital has its own guidelines on DVT prophylaxis and treatment and all healthcare workers should follow them. Once a DVT has developed, the pharmacist should be familiar with the current anticoagulants and their indications. Plus, the pharmacist must educate the patients on the need for treatment compliance and the need to undergo regular testing to ensure that the INR is therapeutic.  [17][19](Level V)

Outcomes

Today close to 300,000 patients die from a pulmonary embolus each year in the US alone. Despite countless guidelines and education of healthcare workers, DVT prophylaxis is often not done. The fact is that DVT is preventable in the majority of patients and the onus is on healthcare workers to be aware of the condition. For those who do develop a DVT and survive, post-thrombotic phlebitis is a lifelong sequela, which has no ideal treatment. [20][21] (Level V)