Venous thromboembolism

Learning objectives • Gain organised knowledge in the subject area

VTE• Be able to correctly interpret diagnostic

information in suspected VTE• Know and apply the relevant evidence and/or

guidelines to different clinical presentations of VTE

• Be aware of common cognitive biases in the diagnosis and management of VTE

Scenarios

Scenario 1

A 34-year-old man was admitted with acute onset of heaviness, pain and functional impairment of his right arm. The arm was cyanotic and swollen. For the past few weeks, he reported transient paraesthesia of his right arm during weightlifting. He had a fracture of the right clavicle after a ski accident 5 years previously which was managed conservatively. There was no personal or family history of thrombosis.

Doppler USS right arm showed axillary and subclavian vein thrombosis

In small groups answer the following Qs:• What are the treatment options in this case?• What further investigations should be

performed?• What follow-up is required?

Upper limb DVT: summary

• Increasing incidence 5-10% all DVTs• Primary– Effort-related thrombosis (Paget-Schroetter Syndrome).

Weights, tennis, repeated overhead activities (swimming, decorating). Most have underlying VTOS

– Idiopathic*• Secondary most common– Indwelling central venous catheters/ports– Cancers, mainly lung and lymphoma– Surgery/trauma/immobilisation of arm– Pregnancy and ovarian hyperstimulation syndrome

Upper limb DVT: summary• Initial management

– Anticoagulation: 3 months for idiopathic and catheter related (if catheter removed); indefinite if on-going risk factors

– Catheter directed thrombolysis / pharmaco-mechanical thrombectomy in selected patients

• Investigations/follow-up– Doppler USS initial investigation of choice– If primary upper limb DVT: imaging of the thorax +/-

thrombophilia screen– If secondary: address underlying cause (e.g. catheter)– OP vascular surgery referral

• Complications– Post-thrombotic syndrome (in one study, 53% pts with upper

limb VTE due to VTOS)

Common cognitive biases in the diagnosis and management of upper limb DVT

• Knowledge gaps application of the wrong heuristic

• i.e. treating upper limb DVT the same as lower limb DVT and applying inappropriate diagnostic, management and further investigation strategies

Any questions at this point?

Scenario 2

• A 50-year-old woman was admitted with pain, redness and swelling of her thigh that had developed over the preceding 48 hours ?cellulitis.

• Her only past medical history was gastro-oesophageal reflux disease and varicose veins.

She was started on iv flucloxacillin by the FY1 doctor

In small groups answer the following Qs:• What is the diagnosis?• What further investigations should be

performed?• What are the treatment options in this case?

Superficial thrombophlebitis: summary

• Inflammation of the superficial veins• Swelling, pain, redness • Scanty evidence base re: management• SIGN guidelines and NICE ‘clinical knowledge

summary’ broadly agree

Superficial thrombophlebitis: summarySIGN Guideline 122• 10-21% of pts have a DVT, more

likely if >5cm inflammation or within 10cm of sapheno-femoral junction

• Topical treatments only alleviate symptoms

• Oral NSAIDs prevent extension, recurrence and progression to DVT, so does LMWH

• Not clear if LMWH (prophylactic or therapeutic doses) is better than NSAIDs – but in high risk cases LMWH recommended*

NICE CKS• The risk of DVT should be

considered• Treat with oral NSAIDs and

paracetamol, class 1 AES and advice. Topical NSAIDs can be used for symptomatic relief

• LMWH not routinely recommended, but experts advise it should be used in high risk cases (no dose recommendation)

• Treat super-added infection with antibiotics

Common cognitive biases in the diagnosis and management of superficial thrombophlebitis

• Knowledge gaps application of the wrong heuristic (i.e. treating as ‘cellulitis’)not knowing the risk of occult DVT at presentation

• Confirmation bias if the patient has been seen first by someone else

Any questions at this point?

Scenario 3

• A 45 year old man presented to Ambulatory Care with right leg swelling and pain, which had occurred spontaneously over the last 3 days

• On examination, his right calf was 5cm wider than the left

• His only past medical history was hypertension

Doppler USS right leg showed a femoral vein thrombosis

In small groups answer the following Qs:• What is the management in this case?

(pharmacological and non-pharmacological)

• What is the duration of anti-coagulation?• What further investigations should be performed?• What follow-up is required?

Duration of treatment?• Cancer patients– 6 months then review

risks/benefits– LMWH only

• Provoked DVT/PE– 3 months then review

risks/benefits

• Unprovoked DVT/PE– 6 months then review

risks/benefits

Question:What is the risk of a recurrent DVT in a 30 year old man who presents with a single unprovoked DVT?

Lower limb DVT: summary• ?DVT history, exam and Wells Score• If DVT suspected plus Wells = likely then do a proximal Doppler USS

(whole leg not recommended)• NICE recommends doing a d dimer in likely cases so that if the proximal

scan is negative they can be offered a repeat scan in one week if their d dimer is high …

• This is because proximal scans may miss calf DVTs that could extend – you don’t need a repeat scan if a whole leg USS was performed first

• If DVT suspected plus Wells = unlikely then get a d dimer, if positive get a scan, if negative DVT is virtually excluded

• For all cases, if you can’t get a Doppler within 4 hours then treat and get a scan within 24 hours

• Consider and communicate alternative explanations for symptoms in patients with negative scans

• Don’t forget to arrange further investigations/FU for new DVT cases

What’s this called?

Common cognitive biases in the diagnosis and management of lower limb DVT

• Groupthink (‘that’s the way we do things around here’)

• Psych-out error and visceral bias (IVDUs)• Omission bias (the tendency towards inaction,

rooted in the principle of ‘first do no harm’ e.g. radiation, anxiety/harm from further Ix, explanation and treatment) …

Any questions at this point?

Scenario 4A 54 year old female smoker was admitted with gradually worsening breathlessness over the last 10 days. She reported a cough but no obvious fever or discoloured sputum. Her past medical history included a DVT 5 years previously.Her chest X-ray showed some patchy consolidation at the left base. She was started on treatment for community acquired pneumonia in ED.

CT or V/Q scan?CTPA• Preferred – simple

positive/negative result, can visualise other lung pathology, RV dysfunction and proximal leg veins

• 90% sensitivity, 95% specificity - a negative CTPA essentially rules out PE

• However, high sensitivity –> increased incidence of PE and probably diagnosing unimportant PEs

V/Q• Recommended in

young/pregnant patients with normal CXRs and no history of lung disease (e.g. asthma) to reduce radiation

• Role in patients who cannot have contrast

• Different sensitivity and specificity figures in literature - non-diagnostic scans with high clinical suspicion still need CTPA

• Much more sensitive than CTPA in diagnosing chronic PEs (e.g. Ix of pulmonary hypertension)

Sensitivity and specificity of V/Q scan(after removing non-diagnostic scans from the analysis)

PE absent Non-diagnostic scan PE present

Normal/very low probability

Low/intermediate probability

High probability

Modified PIOPED ll Scintigraphic Criteria(V/Q result compared with DSA or CTPA + Wells)

Sensitivity 77.4%Specificity 97.7%

The % of patients with a PE absent or PE present scan was 73.5%

Diagnosing PE: things to consider

• Patients required respiratory OP follow up (not small peripheral PEs)

• Over 40’s with idiopathic PEs require cancer screening same as DVTs

• Duration of anti-coagulation same as DVTs• Thrombolysis is considered more often in PE – you need to

know the criteria• Investigation is different in pregnant patients: bilateral leg

Doppler USS first. (Treatment and follow-up for VTE in pregnancy is different too)*

How do you decide whether a patient can be investigated and

treated for PE in Ambulatory Care?

Simplified PE Severity Index (PESI) Score

Patients with a score of 0 are determined to be low risk, while those with a score of 1 or more are considered high risk

PE: summary• ?PE history, exam and Wells Score• If PE suspected plus Wells = likely then image the chest• If PE suspected plus Wells = unlikely then do d dimer

– If the d dimer is raised, remember that it is NOT diagnostic, it just means imaging is required to exclude PE

– If d dimer is negative then PE is virtually excluded• For all cases, if you can’t get imaging within 4 hours then treat

and get a scan within 24 hours• Consider and communicate alternative explanations for

symptoms in patients with negative scans• Don’t forget to arrange further investigations/FU for new PE

cases

Common cognitive biases in the diagnosis and management of PE

• Misinterpretation of diagnostic tests (d dimer, V/Q)

• Knowledge gaps (e.g. different Ix and management in pregnancy)

• Representativeness, premature closure, search satisficing, confirmation bias ..?

Any questions at this point?

Scenario 5A 75-year-old woman was sent to Ambulatory Care for investigation of a raised d dimer (900 μg FEU/L). She had been admitted two weeks previously with pleurisy and had a negative CTPA. On discharge the Practice Nurse repeated the d dimer test to see if it was still raised and referred the patient back to Acute Medicine to ‘find the clot’.

The patient’s past medical history consisted of: COPD, heart failure, hypertension.On examination the patient was well with no new symptoms and had mild bilateral lower leg oedema.

Correct interpretation of d dimer

• Ginsberg and colleagues found that the combination of a low pre-test probability and a normal d dimer had a negative predictive value of 99%, whereas the negative predictive value was only 78% in patients with a high pre-test probability and a normal d dimer

• A rule of thumb is that a ‘positive’ d dimer is non-diagnostic

• However … should a d dimer of 900 be interpreted the same as a d dimer of 10,000?

Any questions at this point?

Summary of Guidelines and MCQs

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