Deep Vein Thrombosis (DVT)

• DVT is Deep Vein Thrombosis

Virchow's Triad

• Describes the three broad categories of factors contributing to thrombosis

Endothelial Damage

• Endothelial dysfunction may be caused by smoking or hypertension
• Endothelial damage may be caused by surgery, catheter insertion (PICC lines), or trauma

Hypercoagulability

• Hereditary factors include Factor V Leiden, Prothrombin G20210A, and Protein C and S deficiency
• Acquired factors include cancer, chemotherapy, OCP/HRT, pregnancy, obesity, and HIT

Stasis

• Stasis is caused by immobility or polycythemia, and it can cause endothelial injury

Other Risk Factors

• Additional risk factors for DVT include smoking, obesity, lower extremity trauma, family or personal history of DVT, and age > 60 years.

Clinical Presentation & Physical Exam

• Leg edema and calf tenderness may be signs of DVT
• Homan's sign, pain during dorsiflexion of the foot, can be present
• Erythema and pain can be present
• Fifty percent of patients may not present symptoms
• Homan's sign is only present in 33% of cases, so is unreliable

Differential Diagnoses

• Other possible diagnoses include superficial phlebitis, cellulitis, ruptured Baker's cyst, strained muscle, and malignant neoplasm compromising a vein

Wells's Score

• Modified Wells Criteria: Clinical Evaluation Table for predicting the probability of a DVT.
• Clinical characteristics with a score of +1: active cancer, paralysis/paresis/recent plaster immobilization of lower extremities, recently bedridden for 3 days or major surgery within 12 weeks, localized tenderness along deep venous system, entire leg swollen, calf swelling ≥ 3cm larger than asymptomatic side, pitting edema confined to symptomatic leg, collateral superficial veins, previously documented DVT.
• Alternative diagnosis at least as likely as a DVT: -2
• Total Score >2 = Likely DVT
• Total Score <2 = Unlikely DVT
• If the score is greater than 2, a diagnostic study must be ordered

Diagnostic Tests

• Duplex venous ultrasound of the leg has 97% sensitivity for proximal DVTs
• Duplex venous ultrasounds cannot detect distal DVTs using a whole leg ultrasound order
• D-Dimer level indicates small fibrin fragments produced and released into the blood when fibrin blood clots are broken down by plasmin- not specific to DVT
• D-Dimer levels will not help with post-surgical patients due to the body's natural inflammatory process after surgery
• False positives can occur with D-Dimer in cases of infection, inflammation, pregnancy, trauma, surgery, and hemorrhage
• Venography/MRI are used to detect iliac vein thrombosis
• D-dimer is less sensitive with distal DVT's

Management

• Patients might be treated as outpatients unless presenting limb ischemia, symptoms of PE, significant comorbidities (ESRD), functional limitations, high bleeding risk, or non-adherence (send to ER)
• Outpatient treatment is possible for calf DVT, clinically stable patients, and patients with a low risk of bleeding
• Coumadin and Pradaxa/Savaysa require at least 5 days of parenteral injection
• Low Molecular Weight Heparin: Enoxaparin 1 mg/kg BID or 1.5 mg/kg OD BID for at least 5 days, Fragmin 100 units/kg BID or 200 units OD
• LMWH +Vitamin K Antagonist: Coumadin 5-10 mg OD for 2 days, then adjusted; 2-3 INR for 24 hours
• LMWH + Abigatran (Pradaxa) 150 BID or Edoxaban (Savaysa) for patients with weight >60 kg: 60 mg once daily, ≤60 kg: 30 mg once daily
• Factor Xa Inhibitor does not require parenteral anti-coagulation
• Eliquis at 10 mg BID for 7 days, followed by 5mg BID
• Xarelto at 15 mg BID for 21 days, followed by 20 mg OD

Inpatient Management

• Unfractionated heparin is preferred in high-risk patients: massive DVT (iliofemoral), severe renal insufficiency, symptoms of PE, high bleeding risk, hemodynamic instability, comorbid conditions, or morbid obesity
• Heparin IV in hospital setting: 80 units per kg intravenous bolus, then maintenance infusion of 18 units/kg/hr of intravenous continuous infusion, further adjustment per/ nomogram
• Transition to Coumadin requires an INR between 2-3 over 24 hours
• Initiate Eliquis, Pradaxa, or Xarelto within 2 hours of discontinuing the heparin infusion

Bleeding Risk Factors

• Risk factors for major bleeding while on anticoagulants include age > 65 years, age > 75 years, alcohol abuse, anemia, antiplatelet therapy, cancer, comorbidity and reduced functional capacity, diabetes mellitus, frequent falls, liver failure, metastatic cancer, poor anticoagulant control, previous bleeding problems, previous stroke, recent surgery, renal failure, and thrombocytopenia

Management Distal DVT

• Patients with distal DVTs are at a lower risk for embolization, approximately half that of proximal DVTs, and resolve spontaneously without therapy
• If symptomatic, treatment is needed; low risk for bleeding
• One-third will develop into proximal veins
• Surveillance with serial ultrasound may be indicated
• Low-risk patients: minor thrombus, no history, negative D-Dimer, non-diagnostic US, or high risk for bleeding
• Survey patients every week for 2 weeks to assess for extension to the proximal veins
• If extension does not occur in 2 weeks, it is unlikely to occur

Anticoagulation Duration

• Reversible Risk Factor (Trauma/Surgery): 3 months
• Recurrent DVT or Clotting factor: indefinite period, hematologist referral
• Oncology Patients: at least 3-6 months if receiving active chemo or have an active cancer diagnosis
• IVC (inferior vena cave filter) is an absolute contraindication for therapeutic anticoagulation, complications from anticoagulation, or failure of anticoagulation in a patient with acute proximal DVT