DEEP VEIN THROMBOSIS

1) Review of the Evidence on Diagnosis of Deep Venous Thrombosis and Pulmonary Embolism2) Duration of anticoagulant therapy after a first episode of an unprovoked pulmonary embolus or deep vein thrombosis

Speaker : Dr. Vinaykumar

Venous system of Lower Limbs

The veins of the lower extremities are divided into three systems:

Superficial Deep Perforating These are located in two main compartments: Superficial Deep

Introduction Deep vein thrombosis and pulmonary

embolism constitute venous thromboembolism. DVT occurs most often in the legs, but can form in the veins of the arms and in the mesenteric and cerebral veins.

Pulmonary embolism is the third most

common cause of mortality by cardiovascular disease after coronary artery disease and stroke.

Epidemiology The incidence of first DVT is 0·5 per 1000

person-years & PE 0.69/1000 person yrs.

The disorder is rare in children younger than 15 years, but its frequency increases with age.

Two-thirds of first-time episodes of deep vein thrombosis are caused by risk factors, including surgery, cancer, immobilization or admission for other reasons.

Risk for first DVT seems to be slightly higher in men (1.3:1.1::male:female per 1000 person-years)

The risk for recurrence of this disorder is higher in men than in women

Risk factors for DVT & PEIdiopathic, primary, and

unprovokedSecondary and

provoked• No apparent cause• Old age (>65 years)• Long distance travel• Associated with thrombophilia (eg, factor V Leiden or prothrombin gene mutation)• Obesity• Cigarette smoking• Hypertension

• Immobilisation• Postoperative• Trauma• Oral contraceptives, pregnancy, postmenopausal HRT• Cancer• Acute medical illness (eg, pneumonia, congestiveheart failure)

Surgery Thrombotic risk depends on the type of surgery

and presence of additional risk factors. The approximate risk for DVT following general

surgery procedures is 15 - 40%. Risk nearly doubles after hip or knee

replacement surgery or hip fracture surgery by 40 -60%

High risk surgeries : Orthopaedic, major vascular and neurosurgery.

Trauma Risk for thrombosis is high in patients with

spinal injuries, pelvic fractures, or leg fractures

• In patients with first spontaneous DVT, the annual likelihood of recurrence is 5–15%.• Risk is low in patients with postoperative deep vein thrombosis.

History of deep vein thrombosis

Cancer Cancer patients who undergo surgical treatment

or chemotherapy have a high risk of VTE. Tumors of the bone,ovary, brain, and pancreas

are associated with the highest incidence of VTE

Treatment of VTE in cancer patients is challenging because of high rates of anti-coagulant associated bleeding and treatment failures.

Travel Traveling in general found to increase the risk of

VTE by 2-fold The risk of flying is similar to the risks of traveling

by car, bus, or train. The risk is highest in the first week after traveling, High relative risk of VTE in individuals with factor

V Leiden, BMI > 30 kg/m2, Tall, OCPs, Even short people has increased risk of VTE

after air travel.

Paediatric DVT Deep venous thrombosis in children is

frequently related to central venous lines.

The frequency of pediatric DVT related to CVL is 11-50%

Typical symptoms of thrombosis are frequently absent.

Pregnancy Pregnant women have a much higher

risk of VTE Risk is higher after caesarian section

than after vaginal delivery. The incidence appears to be highest in

the postpartum period.

Thrombophilia

Several distinct abnormalities in the coagulation system are associated with increased risk for DVT.

These defects are generally inherited and detected with first spontaneous thrombosis.

Antibodies against phospholipids Antibodies against phospholipids (lupus

anticoagulant), cardiolipin or glycoprotein interact with phospholipids or plasma proteins bound to an anionic surface.

The prevalence in unselected patients with DVT is about 5%.

The lupus anticoagulant confers a tenfold increased risk for first thrombosis and is a risk factor for recurrence,

Natural inhibitor deficiencies

Antithrombin III is a potent inhibitor of several coagulation proteases. The frequency of antithrombin deficiency <1% in unselected patients with VTE.

Protein C is a vit K-dependent glycoprotein, the frequency of deficiency is 3·2% of unselected patients with VTE.

Protein S is a vit K-dependent glycoprotein and a cofactor for protein C. This deficiency was reported in 7·3% of unselected patients with DVT.

Deficiency confers >8 fold increased risk for DVT

High clotting factor levels Raised concentration of factor VIII, IX, factor XI

is an independent risk factor of first spontaneous DVT.

The mechanisms of thrombosis is unclear. High factor VIII is a potent risk factor for

recurrence of DVT.

CLINICAL PROBABILITY SCORING SYSTEM

Wells score for DVT ScoreCancer +1

Paralysis or recent plaster cast +1

Bed rest >3 days or surgery <4 weeks +1

Pain on palpation of deep veins +1

Swelling of entire leg +1

Diameter difference on affected calf >3 cm +1

Pitting oedema (affected side only) +1

Dilated superficial veins (affected side) +1

Alternative diagnosis at least as probable as DVT –2

Patients with a score of 0 : low risk, 1–2 : intermediate risk,≥3 : high risk

Wells score for PE ScorePrevious PE or DVT +1・ 5

Heart rate >100 beats per min +1・ 5

Recent surgery or immobilisation +1・ 5

Clinical signs of DVT +3

Alternative diagnosis less likely than PE +3

Haemoptysis +1

Cancer +1

For the initial rule, patients with a score of 0–1 : low risk2–6 : intermediate risk≥7 : high risk;

For the dichotomised rule, score ≥4 likely to have PE score≤4, unlikely to have PE

Revised Geneva score for PE Score

Age >65 years +1

Previous DVT or PE +3

Surgery (under general anaesthesia) or fracture (of the lower limbs) within 1 month

+2

Active malignancy (currently active or considered as cured since less than 1 year)

+2

Unilateral leg pain +3

Haemoptysis +2

Heart rate 75–94 beats per min +3

Heart rate ≥95 beats per min +5

Pain on deep vein palpation in leg and unilateral oedema +4

Patients with a score<2 : low risk, 2–6 : intermediate risk,≥6 : high risk.

DIAGNOSIS

Clinical Assessment

Clinical features of DVT

Localised tenderness Swollen leg Calf swelling 3 cm greater than asymptomatic

leg Pitting oedema Collateral superficial veins (non-varicose)

Clinical features of Pulmonary Embolism

The symptoms and signs of PE are not specific. Severe cases of PE can lead to collapse or

sudden death.In the majority of the fatal cases the PE is not clinically diagnosed prior to death.

Symptoms include: Dyspnoea. Pleuritic chest pain, retrosternal chest

pain. Cough and haemoptysis. In severe cases, right heart failure

causes dizziness or syncope.

Signs include: Tachypnoea, tachycardia. Hypoxia, which may cause anxiety,

restlessness, agitation and impaired consciousness.

Pyrexia. Elevated jugular venous pressure. Systemic hypotension and cardiogenic

shock.

Laboratory studies

Fibrin D-Dimer measurement

Plasma D-Dimer is a degradation product of cross linked fibrin and its levels increase in plasma of patients with acute VTE.

DD assay is highly sensitive (>98%) in acute DVT or PE (cutoff value of 500 mg/l) Hence, a DD level below this value reasonably rules out acute VTE.

Sensitivity is very high but specificity of fibrin for VTE is poor, because fibrin is produced in a wide variety of conditions such as cancer, inflammation, infection or necrosis.

D-Dimer >500 mg/l has a poor positive predictive value for VTE. So it must be combined with clinical probability in order to safely rule out VTE.

Imaging Techniques

Venography

was considered the diagnostic standard for diagnosing DVT but it is invasive, costly and not devoid of risk. It is still used as surrogate end point in thrombo

prophylactic trials.

Although gold standard for diagnosing PE, pulmonary angiography is difficult to interpret, frequent disagreement occurring even between expert readers, more often on the absence (17%) than on the presence of PE (8%).

Pulmonary angiography

Compression ultrasonography (CUS)

Lower limb compression venous USG, a noninvasive test with sensitivity of 97% & specificity of 98% for symptomatic proximal DVT.

The single well-validated diagnostic criterion for DVT on CUS is absence of full compressibility of the deep vein when applying pressure through the ultrasound probe.

Ventilation/perfusion lung scintigraphy Perfusion lung scintigraphy is a noninvasive technique

allowing the visualisation of pulmonary perfusion through IV albumin macroaggregates labelled by technetium 99. These are trapped in pulmonary capillary vessels and imaged by a gamma camera.

Pulmonary hypo-perfusion is not highly specific for an embolus, since any disease that narrows the airways or fills the alveoli with fluid will result in hypoxic pulmonary vasoconstriction.

A perfusion defect corresponding to a segment or a large part of a segment is more specific for PE.

The addition of ventilation scintigraphy(by xenon 133, krypton 81 or aerosolised technetium 99)

further increases specificity, a so-called mismatched defect (perfusion defect with normal ventilation) representing PE.

lung scan results are classified into three categories: normal, high probability and non diagnostic

Attribution of a lung scintigram to the high-probability category requires two or more mismatched segmental defects or, if only one is present, the addition of two large mismatched sub segmental defects

Spiral CT scan

Spiral CT scanning allows an adequate visualisation of the pulmonary arteries up to segmental level. With sensitivity 70% & specificity of 90%..

Multi-detector CT is highly sensitive, which allows both a thinner collimation (1–2mm collimation) and a better definition of the picture.

CT angio has largely replaced ventilation perfusion scan as main imaging modality in PE

The probability of PE is very low in patients with a low or intermediate clinical probability, absence of proximal DVT and a negative spiral CT.

Echocardiography Doppler echocardiography is not a diagnostic tool,

but in suspected PE it may play a role in risk stratification.

In 4% of patients, transthoracic echo allows direct visualisation of the clot in the right heart chambers or in the right main pulmonary artery.

Echocardiographic manifestations of PE are acute increase in pulmonary arterial resistance and pulmonary hypertension.

Signs : dilation of the right ventricle, hypokinesis, and in severe cases, paradoxical motion of the interventricular septum.

In patients with shock, it is extremely effective

for differential diagnosis with tamponade and cardiogenic shock.

Magnetic Resonance Venous Imaging (MRVI)

Help in the imaging of more proximal venous disease.

Useful test for imaging iliac veins, IVC, calf vein & recurrent DVT and area where the use of duplex ultrasound is limited.

Massive PE In highly unstable patients start thrombolytic

treatment.

If patient is temporarily stabilised by vasopressive drugs, diagnosis is confirmed by either lung scan or spiral CT.

Recurrent deep vein thrombosis Clinical assessment of recurrent ipsilateral DVT

is hampered by the similarity between symptoms of post-thrombotic syndrome and acute DVT.

Use of ultrasonography is limited because abnormalities in the proximal veins and comparison with previous USG results needed.

Diagnosis of recurrent DVT requires the detection of a new non-compressible segment by USG.

If the result is nondiagnostic or negative, with high clinical probability, venography should be done.

Chronic thromboembolic pulmonary hypertension

Defined as a mean pulmonary artery pressure greater than 25 mm Hg that persists 6 months after diagnosis of pulmonary embolism.

The disorder occurs in 2–4% of patients after acute pulmonary embolism and results in disabling dyspnoea, both at rest and with exertion.

Post-thrombotic syndrome of the leg

Post-thrombotic syndrome of the leg arises in 20-50% of patients with first proximal DVT who has received standard treatment with anticoagulants.

PTS include chronic calf swelling with brownish skin pigmentation and in extreme circumstances venous ulceration of the skin.

Risk factors are recurrence in the ipsilateral leg and possibly proximal thrombosis.

In most people, the disorder arises within 2 years.

Deep vein thrombosis of the arms

Symptoms include pain, oedema, and cyanosis.

Deep vein thrombosis of the arms arises as a complication of central venous catheters, or idiopathic (0·02 /1000 people per year)

On clinical suspicion, compression CUS is the preferred diagnostic method.

If USG is inconclusive or negative despite a high clinical probability, venography should be done.

Treatment

Initial treatment Fixed-dose, weight adjusted, subcutaneous

LMWH is treatment of choice. Dose, 1mg/kg body weight twice daily or 2mg/kg

body weight once daily. Because of its shorter half-life, unfractionated

heparin might be used in surgical patients with DVT in whom rapid reversal of anticoagulation is necessary.

Thrombolytic therapy It should be reserved for patients with limb-

threatening thrombosis

Given either systemically or via local catheter-directed infusion.

Vena cava filters In patients with proximal DVT Vena cava filters are thrombogenic and double the

recurrence risk. They used selectively in patients with

contraindications to anticoagulants, recurrent PE despite adequate anticoagulation, chronic thromboembolic pulmonary hypertension.

Endovascular reconstruction Recanalisation of occluded iliac vein is

performed endovascularly. Balloon dilatation is then performed and

stent is placed across the dilated segment.

This is the first line therapy for iliac vein occlusions.

Long-term prevention

vitamin K antagonists started simultaneously with heparin (same day)

The dose is titrated to achieve INR between 2-3.

Heparin can be discontinued after 5–7 days, as long as the ratio is stable and is 2·0 or greater.

REVIEW OF THE EVIDENCE ON DIAGNOSIS OF DEEP VENOUS

THROMBOSIS AND PULMONARY EMBOLISM

Ann Fam Med 2007;5:63-73.

Topic 1

This journal summarizes the evidence regarding the efficacy of techniques for diagnosis of deep venous thrombosis (DVT) and pulmonary embolism.

INTRODUCTION The incidence of isolated DVT is around

50 per 100,000 person-years 30% of patients with DVT develop

symptomatic PE and another 40% have asymptomatic PE.

Article Review Process and Data Abstraction

They reviewed 22 systematic reviews and 36 primary studies.

CLINICAL PREDICTION RULES

Result Results provide strong evidence to support

the use of a clinical prediction rule for establishing the pretest probability of disease in a patient before more definitive testing.

Use of a D-dimer assay with a clinical prediction rule has a very high negative predictive value.

The Wells prediction rule was most frequently evaluated in these studies

Pretest probability for DVT Prevalence

High 17 - 85%.

Moderate 0 - 38%

Low 0 - 13%.

Wells prediction rule evaluated for pulmonary embolism

Pretest probability for PE PrevalenceHigh 38 - 78%.

Moderate 16 - 28%

Low 1 - 3%.

Geneva prediction rule evaluated for pulmonary embolism Pretest probability Prevalence

High 77 – 85%

Moderate 34 -35%

Low 7%

Clinical prediction rule with a D-dimer assay.

Result of studies

D-dimer assay & pretest probability 3-month incidence of VTE

-ve DD + low PTP 0.5%

-ve DD + moderate PTP 3.5%

-ve DD + high PTP 21.4%

D-DIMER MEASUREMENT

Studies evaluating enzyme-linked immunosorbent assays (ELISA) and latex turbidimetric assays for diagnosis of PE.

D-dimer cutoff of was 500 ng/mL.

Sensitivity Specificity

ELISA assays 95% 45%

Latexturbidimetric assay

93% 51%

It is concluded that both tests are highly sensitive and clinically useful in excluding disease with low to moderate clinical probability of pulmonary embolism.

D-dimer assay in patients with symptoms of lower extremity DVT

Results In many studies sensitivity of the assay was

<90%, making it insufficiently sensitive to “rule out” a diagnosis of DVT.

The performance of the assays was affected by the relevance of DVT in the population and the choice of reference test.

More sensitive for diagnosing thrombus above the knee than for diagnosing calf-vein thrombosis.

D-dimer assays used for either DVT or PE diagnosis

Authors included all types of D-dimer assays. The pooled sensitivities and specificities

were highest for ELISA and Quantitative rapid ELISA

Sensitivity Specificity

DVT PE

ELISA 95% 96% 40 - 50%

Quantitative rapid ELISA

96% 97% 40 - 50%

The authors concluded that the negative predictive values for ELISA assays, are sufficiently high that these assays should be able to stand alone in excluding a diagnosis of DVT or PE.

ULTRASONOGRAPHY

Studies that summarized the accuracy of USG (with or without color Doppler) for the diagnosis of DVT using contrast venography as the reference standard.

The reviews included studies of symptomatics, asymptomatic patients or both.

Studies to detect thrombosis of the proximal veins, distal veins or both.

Result USG has high sensitivity and specificity for

diagnosing proximal DVT. In high-risk asymptomatic patients (Post-op)

specificity is high but sensitivity may be diminished;

Sensitivity for detecting calf vein thrombosis is poor.

For the diagnosis of symptomatic thrombosis in the proximal veins, the reviews reported sensitivities of 89 - 96% and specificities 94 - 99%.

For detection of asymptomatic thrombi in proximal veins, the reviews suggested that high specificity but low sensitivity.

Sensitivity Specificity

Symptomatic calf vein thrombosis

gottlieb et al 93% 99%

Other reviews 73-75%

Asymptomatic calf vein thrombosis Around 50%

Symptomatic upper extremities 56 -100% 77 -100%

HELICAL CT

10 systematic reviews summarizing the accuracy of helical CT for the diagnosis of pulmonary Embolism shows,

Sensitivity Specificity

Helical CT 66 -93% 89 -98%

9 prospective studies with pulmonary arteriography as the reference standard.

Only 4/9 studies reported sensitivity >90% 6/9 studies reported specificity >90%.

Sensitivity Specificity

45 -100% 78 -100%

The published literature has not kept up with advances in CT technology (high-resolution multidetector CT)

Only 1 study showed the accuracy of Multi detector CT angio which reported a sensitivity of 100%.

Clinical assessment with Multidetector CT angiography

High Intermediate Low

Positive predictive value

96% 92%

Negative predictive value

96%

In review of 25 studies, 2 strategies were highly effective in excluding pulmonary embolism

(1) Normal results on pulmonary angiography or lung scintigraphy

(2) Normal D-dimer with low clinical probability.

CONCLUSION The evidence strongly supports the use of

clinical prediction rules for establishing the pretest probability of DVT or PE in a patient before more definitive testing.

D-dimer assay with a clinical prediction rule has a high negative predictive value.

D-dimer, in isolation also has strong negative predictive values for detection of DVT and PE.

USG is a good testing modality for diagnosing proximal VTE in symptomatic patients, but it is less accurate in distal veins, upper extremity veins, and in asymptomatic patients.

Multidetector CT has high sensitivity and positive predictive value for diagnosing PE.

Multidetector CT becoming the norm in many hospitals for diagnosing PE.

Topic 2

Duration of anticoagulant therapy after a first episode of an unprovoked

pulmonary embolus or deep vein thrombosis: guidance from the ISTH

Journal of Thrombosis and Haemostasis, 10: 698–702

Scope and methodology Unprovoked PE and DVT are defined as those

occurring in the absence of an antecedent (within 3 months) surgical or nonsurgical risk factor.

Account for 25% to 50% of all patients with VTE.

Definition of termsThe definitions of duration of anticoagulation are:1 Initial anticoagulation: 3–6 months of treatment;2 Long-term (indefinite) anticoagulation: > 3–6

months of treatment with no definite stop time which could be either lifelong or until the perceived bleeding risk precludes continuation of anticoagulation.

PE and Lower limb DVT A period of adequate vitamin K antagonist (VKA)

anticoagulation with a target INR of 2.5 (range 2–3) is required to prevent extension of thrombus and prevent early recurrence (within the first 3-6 months). Long-term anticoagulation is required to prevent late recurrence.

The benefit of anticoagulation continues only for as long as therapy is continued.

Duration of initial anticoagulation

Patients with unprovoked isolated distal (calf vein) DVT have a risk of recurrence that is about half that of a proximal DVT or PE and the recurrence rate after 3 months of anticoagulation appears to be lower than with shorter duration treatment.

At least 3 months of anticoagulant therapy is required to prevent extension of thrombus and prevent early recurrence after a first PE and/or proximal DVT.

However, 6 months of initial anticoagulation of patients with unprovoked PE or proximal DVT appears to offer a lower risk of early recurrence than 3 months of treatment.

Guidance statements1 Patients with an unprovoked calf DVT should

be treated for 3 months.2 Patients with an unprovoked PE or proximal

DVT should be treated for 3 to 6 months.

Continued anticoagulation beyond the initial 3-6 month period

Patients with unprovoked venous thrombosis have an annual risk of recurrence > 5%, this risk exceeds the risk of VKA-related bleeding,

Patients with a first or recurrent episode of unprovoked PE or proximal DVT should be considered for long-term anticoagulation.

They should be treated initially with 3 months anticoagulant therapy and then considered for long-term (potentially lifelong) anticoagulation depending on their risk of bleeding.

Patients with a PE and DVT provoked by surgery are at low risk of recurrence (annual risk< 1%) after completion of 3-months oral anticoagulants, so longer therapy is not routinely required.

PE or DVT associated with non-surgical risk factors have a variable risk of recurrence, The duration of anticoagulation should be influenced by the perceived risk in individual patients.

Long-term anticoagulant therapy generally

be reserved for patients with no identifiable antecedent risk factor.

Guidance statements

1 For Unprovoked calf DVT, anticoagulant therapy for longer than 3 months is not required.

2 Unprovoked PE or proximal DVT anticoagulation should be considered for as long as the perceived risk of anticoagulant-related bleeding is not so high as to preclude continued treatment.

3 Patients with a provoked PE and DVT anticoagulant therapy after 3 months is not required.

Hormone-associated PE and DVT

Defined as a PE/DVT occurring in women who are receiving estrogen-containing hormonal therapy (OCP / HRT) and do not have additional risk factors.

Prognosis is generally good.

Approximately 50% lower risk for thrombosis recurrence compared with women with an unprovoked VTE occurring in the absence of hormonal use.

These Women are advised to stop this preparation.

Patients with strong gynecological indications or a personal preference for hormonal treatment are combined with continued anticoagulant therapy.

Guidance statements

1 Women with a hormone associated VTE if hormone therapy is stopped at the time of diagnosis, anticoagulants are given for 3 months.

2 In premenopausal women an effective alternative

contraception must be utilized to avoid the potential toxicity of early fetal warfarin exposure.

3 Hormonal therapy can be continued in selected patients if there is a strong clinical indication but anticoagulant therapy should be continued for the duration of hormonal therapy.

Risk of bleeding and quality of anticoagulant therapy

Major determinants of bleeding as a result of VKA therapy include:

(i) Advanced age; (ii) Previous bleeding;(iii) Increased (or variable) intensity of anticoagulation; (iv) Comorbidities such as renal or hepatic impairment(v) Concomitant use of drugs that affect hemostasis,

(aspirin / clopidogrel)(vi) Duration of therapy.

Factors to predict risk of recurrence

D-dimer Individual risk of recurrence is

heterogeneous. Lower annual risk in patients with a low D-

dimer(~4%) result after completion of initial VKA therapy compared with those with a high D-dimer (~9%).

Residual vein occlusion Residual vein occlusion, as detected by venous

ultrasound, does not predict a likelihood of a recurrent DVT to a degree that is clinically useful.

Post-thrombotic Syndrome Post-thrombotic syndrome (PTS) is associated with

a 2.6 fold increased risk of recurrence after unprovoked DVT.

PTS is associated with a high D-dimer.

Thrombophilia Testing for heritable thrombophilic defects

does not usefully predict likelihood of thrombosis recurrence after a first episode of VTE.

Male Gender Males appear to be at 1.8-fold higher risk of

recurrence after an episode of an unprovoked VTE.

Mode of clinical presentation Patients with an initial unprovoked PE are 3-4

times more likely to suffer recurrence as a PE rather than DVT.

And the risk of a fatal PE is 2-4 times more likely in patients with a symptomatic PE as compared with patients with a symptomatic DVT alone.

Guidance statements1) It is not possible to give a definitive guidance

statement as to which patients should or should not receive long-term anticoagulant therapy after an episode of an unprovoked PE or DVT.

Patients should be assessed on an individual basis, taking into consideration factors contributing to thrombosis recurrence risk and bleeding risk.

2 ) Following factors may favor long-term anticoagulation in patients with a first unprovoked PE or DVT:

a. Male gender;b. Moderate-to-severe post-thrombotic syndrome;c. Ongoing dyspnoea (possibly related to

unresolved or recurrent PE);d. Satisfactory initial anticoagulant control;e. Elevated D-dimer result.

3) Following factors may favor stopping anticoagulation in patients with a first unprovoked VTE:

a. Female gender;b. Absent or mild post-thrombotic syndrome;c. Unsatisfactory initial anticoagulant control;d. Low D-dimer result.

Upper limb DVTInitial anticoagulant therapy for upper limb VTE is

the same as for the lower limb. Most cases of an upper limb DVT are provoked by

central venous catheters.

Long-term anticoaulant therapy is not routinely required even if DVT is unprovoked as the recurrence rate appears to be low(<5%).

Risk factors that may indicate consideration of continued anticoagulation

Persistent thoracic outlet syndrome, Severe post-thrombotic syndrome The continued use of an indwelling central venous

catheter.

Vascular surgical intervention can be undertaken for severe thoracic outlet syndrome.

Guidance statements Unprovoked upper limb DVT should be

treated for 3 months initially. Long-term anticoagulant therapy is not

routinely indicated in the absence of continuing risk factors(central venous catheter, persistent thoracic outlet syndrome or severe post thrombotic syndrome)

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