DVT complete diagnostic approach resident survival guide

Overview

Deep vein thrombosis (DVT) is the formation of a blood clot, also known as thrombus, in a deep vein. The initial diagnostic test for a suspected DVT is either D-dimer or proximal ultrasound depends the pretest probability of the disease. The treatment of proximal DVT or isolated distal DVT that are selected for anticoagulation therapy includes parental anticoagulation therapy for at least 5 days and until the INR is equal or more than 2 for more than 24 hours, in addition to long term treatment with oral anticoagulation therapy.

Complete Diagnostic Approach

A complete diagnostic approach should be carried out after a focused initial rapid evaluation is conducted and following initiation of any urgent intervention.

Characterize the symptoms in the involved extremity: ❑ Swelling ❑ Pain ❑ Erythema ❑ Warmth

Identify possible precipitating factors: ❑ Recent surgery ❑ Hospitalization ❑ Trauma ❑ Pregnancy ❑ Postpartum ❑ Heart failure ❑ Immobility ❑ Recent bed rest ❑ Recent cast of lower extremities ❑ Obesity ❑ Active malignancy ❑ Treatment for malignancy within the last 6 months ❑ Stroke ❑ Paralysis ❑ Paresis ❑ Oral contraceptive or hormone replacement therapy Obtain a detailed history: ❑ Previous episode of VTE ❑ Age ❑ Location ❑ Past medical history: ❑ Atherosclerosis ❑ Collagen vascular disease ❑ Heart failure ❑ Myeloproliferative disease ❑ Nephrotic syndrome ❑ History of thrombophilia ❑ Factor V Leiden mutation ❑ Prothrombin gene mutation G20210A ❑ Protein C or S deficiency ❑ Antithrombin (AT) deficiency ❑ Antiphospholipid antibody syndrome ❑ Abortion at second or third trimester of pregnancy (suggestive of an inherited thrombophilia or APS) ❑ Drugs that may induce APS ❑ Hydralazine ❑ Phenothiazine ❑ Procainamide

❑ Examine the patient: Extremities ❑ Unilateral calf or thigh tenderness ❑ Unilateral calf or thigh pitting edema ❑ Unilateral calf or thigh swelling ❑ Difference in calf diameters > 3 cm (the calf circumference is measured 10 cm below the tibial tuberosity) ❑ Difference in thigh diameters (the thigh circumference is measured 10-15 cm above the patella) ❑ Unilateral calf or thigh warmth ❑ Unilateral calf or thigh erythema ❑ Palpable cord (a thickened palpable vein suggestive of thrombosed vein) ❑ Dilatation of unilateral collateral superficial veins ❑ Localized tenderness upon palpation of the deep veins ❑ Posterior calf ❑ Popliteal fossa ❑ Inner anterior thigh ❑ Homan's sign: tenderness upon dorsiflexion of the foot (not reliable) ❑ Generalized edema (suggestive of nephrotic syndrome) Abdominal exam ❑ Ascites (suggestive of Budd Chiari syndrome, that is hepatic vein thrombosis) ❑ Hepatomegaly (suggestive of Budd Chiari syndrome, that is hepatic vein thrombosis)

Assess the pretest probability of DVT (Wells score shown below)

Consider alternative diagnoses: ❑ Muscle strain or muscle tear ❑ Immobilization that led to leg swelling ❑ Lymphedema ❑ Lymphangitis ❑ Chronic venous insufficiency ❑ Venous obstruction ❑ Baker's cyst ❑ Cellulitis ❑ Superficial thrombophlebitis ❑ Hypoproteinemia ❑ Nephrotic syndrome ❑ Cirrhosis

Order tests: ❑ CBC-D ❑ PT and aPTT ❑ Creatinine ❑ Liver function test

Is the suspected DVT a first or a recurrent episode?

First suspected episode

Suspected recurrent episode

Assess the pretest probability of DVT (Wells score shown below)

(Click here for the diagnostic approach)

Low pretest probability (Click here for the diagnostic approach)

Moderate pretest probability (Click here for the diagnostic approach)

High pretest probability (Click here for the diagnostic approach)

Initial Anticoagulation Choices (DVT)

❑ SC low molecular weight heparin (1st line)

❑ Enoxaparin 1.0 mg/kg every 12 hours OR 1.5 mg/kg once daily

❑ Tinzaparin 175 U/kg once daily

❑ SC fondaparinux (1st line)

❑ 5 mg once daily (if body weight <50 kg)

❑ 7.5 mg once daily (if body weight <50-100 kg)

❑ 10 mg once daily (if body weight >100 kg)

❑ IV unfractionated heparin

❑ 80 U/kg as bolus, followed by 18 U/kg/h, OR

❑ 70 U/kg as bolus, followed by 15 U/kg/h for stroke or cardiac patients

❑ Adjust the dosages according to the aPTT

❑ SC unfractionated heparin

❑ 333 U/kg as bolus, followed by 250 U/kg

Anticoagulation for VTE

Warfarin

• Begin with 10 mg warfarin for 2 days followed by dosing based on the INR
• Start at the 1st or 2nd day of the initial parenteral therapy
• Target INR is 2-3
• Monitor INR:
  • If stable, repeat INR every 12 weeks
  • If stable but one value 0.5 below or above the target range, continue the same dose and repeat INR within 1-2 weeks
• Avoid NSAIDs, COX2 selective NSAIDs and some antibiotics

Heparin

IV-UFH

• 80 U/kg as bolus, followed by 18 U/kg/h
• 70 U/kg as bolus, followed by 15 U/kg/h for stroke or cardiac patients

SC-UFH

• 333 U/kg as bolus, followed by 250 U/kg

LMWH: decrease dose in renal insufficiency (Creatinine clearance < 30 mL/min)

Fondaparinux

• 7.5 mg daily
• 10 mg daily if weight>100 Kg

Long Term Treatment

Shown below is the long term treatment for DVT. Note that not all patients with isolated distal DVT are started on anticoagulation, only those who are started require long term therapy with anticoagulation. Patients who are planned to receive long term therapy with anticoagulation should be assessed regularly for the risks vs benefits of anticoagulation therapy.

Is the DVT provoked or unprovoked?

Provoked

Unprovoked

What is the predisposing factor?

Is this the first or second episode?

Surgical OR Transient non surgical predisposing factor

Cancer

First episode

Second episode

Therapy for 3 months ❑ VKA (first line) OR ❑ LMWH (2nd line) OR ❑ Dabigatran OR ❑ Rivaroxaban

Extended therapy or until cancer is cured ❑ LMWH (first line) OR ❑ VKA (2nd line) OR ❑ Dabigatran OR ❑ Rivaroxaban

Is the DVT proximal or distal?

What is the risk of bleeding?

Proximal DVT

Isolated distal DVT

Low or moderate risk of bleeding

High risk of bleeding

What is the risk of bleeding?

Therapy for 3 months (irrespective of the risk of bleeding) ❑ VKA (first line) OR ❑ LMWH (2nd line) OR ❑ Dabigatran OR ❑ Rivaroxaban

Extended therapy ❑ VKA (first line) OR ❑ LMWH (2nd line) OR ❑ Dabigatran OR ❑ Rivaroxaban

Therapy for 3 months ❑ VKA (first line) OR ❑ LMWH (2nd line) OR ❑ Dabigatran OR ❑ Rivaroxaban

Low or moderate

High

Extended therapy ❑ VKA (first line) OR ❑ LMWH (2nd line) OR ❑ Dabigatran OR ❑ Rivaroxaban

Therapy for 3 months ❑ VKA (first line) OR ❑ LMWH (2nd line) OR ❑ Dabigatran OR ❑ Rivaroxaban

Do's

• If long term anticoagulation is extended for a longer period beyond 3 months, the same drug initially started should be continued.
• Treat incidentally found asymptomatic DVT just like symptomatic DVT.
• For the long term management of DVT patient:
  • Educate the patient about the long term therapy with anticoagulation
  • Recommend comopression stockings for 2 years to prevent post-thrombotic syndrome.
• Among patients started on heparin, if the risk of heparin induced thrombocytopenia is more than 1%, monitor platelet count every 2 to 3 days from the 4th until the 14th day of treatment or until the discontinuation of heparin.
• Screen for thrombophilia if this is a first episode of VTE in a patient less than 50 years of age.