Question 20

 

b)

Treatment: (50% Marks)

Treatments aim to alleviate the symptoms, prevent thrombin propagation and pulmonary embolism, and prevent post-thrombotic syndromes.

1. Anti-coagulation:
   • Initiate with unfractionated heparin infusion or low molecular weight heparin (preferred)
   • Followed by either low molecular weight heparin or oral anticoagulants for 3 to 6 months
2. Thrombolysis:
   • Limited evidence
   • Catheter-directed thrombolysis is upper limb has extensive swelling and functioned impairment
3. Mechanical catheter intervention:
   • Aspiration of the thrombus, fragmentation and thrombectomy should be considered in patients with persistent severe symptoms, despite anticoagulation or thrombolysis.
4. SVC filters:
   • Evidence is lacking
   • Prevention of pulmonary embolism in patients with ULDVT in whom anticoagulation is contraindicated or thrombus progression despite anticoagulants.
   • Significant complications including cardiac tamponade and aortic perforations reported.
5. Catheter/device removal:
   • No need for routine removal
   • Remove if infected
   • Factors to be considered include the ongoing need for the catheter and difficulty in venous access.

(Highlighted points in treatment section are required for a pass mark.)

Examiners Comments:

Topic was poorly understood, with little knowledge beyond superficial. It was suspected that that relates to poor exposure and experience of more advanced interventions (thrombolysis, possible radiology directed treatments). Little was mentioned around importance of lines in thrombosis and almost everyone who remembered wanted to pull the lines out without thought or consideration of the implications.

Discussion

Risk factors for upper limb DVT from Kommareddy et al (2002):

Gene mutations Factor V (G1691 A) Prothrombin (G20210A) Methylene-tetrahydrofolate reductase MTHFR (C677T) Protein C Protein S Fibrinogen Antithrombin

Acquired thrombophilias Cancer Congestive heart failure Pregnancy Antiphospholipid syndrome Nephrotic syndrome Liver disease Disseminated intravascular coagulation Sepsis Heparin-induced thrombocytopenia Vasculitic disorders Inflammatory bowel disease

Other factors Thoracic outlet syndrome Strenuous effort Central venous catheters Implanted pacemakers Trauma Previous thrombosis Antineoplastic agents Oral contraceptives

Specific difference between upper limb and lower limb DVT risk factor profiles, according to Cote et al (2017): 

• Recent surgery was less common in the upper limb DVT patients (12% vs 18%)
• Malignancy was more common (50% had a malignancy, vs 30%)
• Age was less of a risk factor (younger patients developed upper limb DVTs), except where the upper limb clot was provoked by a catheter
• Immobility was much less of a risk factor (19% vs 43% for lower limb DVT)
• Oral contraception or hormone replacement therapy was twice as common among the upper limb DVT group (20% vs 9.2%)
• Upper limb central lines were a major risk factor.

Clinical features:

• Generic clinical features of DVT:
  • Pain
  • Limb swelling
  • Oedema
  • Paraesthesia
  • Cord-like structure on palpation
  • Redness due to phlebitis
  • Coolness due to poorer perfusion
  • Decreased mobility or dexterity of the limb
• Features unique to upper limb DVT:
  • Neck stiffness
  • Facial swelling
  • Pemberton's sign (with SVC obstruction)
  • Failure to insert upper limb CVCs ("the catheter just won't thread")
• There are also a few clinical features unique to catheter-associated DVTs:
  • Inability to withdraw blood from the catheter
  • Inability to inject into the catheter
  • Loss of transducer waveform

Investigations:

• DSA or plain radiocontrast venography is the gold standard
• Ultrasound is substituted in virtually every situation as a nontoxic noninvasive alternative
• Imaging with CT venography is the main approach to diagnosis if ultrasound is not available or for some reason uninformative (eg. the patient is covered in burns dressings). Additionally, CT of the veins is often the only way to map the venous circulation of the mediastinum and the pelvis.
• Impedance plethysmography (Hull et al, 1986) where the electrical impedance of the limb is measured with electrodes before and after cuff deflation

• Molecular tracer imaging (Houshmand et al, 2014), where the patient is injected with a radioactive tracer which binds to the clot and reveals it on a scintigraphy scan (PET/CT).

Management:

Guidelines from the American College of Chest Physicians (Kearon et al, 2012) recommend the following anticoagulation regimen:

• Isolated brachial vein thrombosis: 
  no anticoagulation unless symptomatic or associated with a CVC
• Proximal, provoked by some significant factor, which is now gone:
  anticoagulant therapy for 3 months. 
• Proximal and associated with malignancy:
  anticoagulant therapy for 3-6 months.
• Proximal and associated with a central line:
  anticoagulant therapy for 3 months if you removed it;
  or, anticoagulant therapy until you decide to take it out.

In addition to this (not instead of it), one may need acute intervention:

• Systemic thrombolysis (not recommended but is one of the options)
• Regional thrombolysis (i.e. you pick a vein distal to the clot and inject a small amount of thrombolytic agent into it)- generally not recommended but is one of the options
• Catheter-directed thrombolysis (where a central venous catheter is introduced into the clot from a distant site, and then used to infuse the clot with a thrombolytic agent) - not very popular since the ATTRACT trial (Vedantham et al, 2017) which demonstrated an increased risk of bleeding without much of an improvement in patient-centred outcomes
• Surgical thrombectomy for patients in whom no other method is available
• Vena cava filter placement is mentioned by the college in the management strategies for DVT, but this makes no logical sense as the filter itself does nothing to treat the DVT, unless one accidentally fragments the clot with their filter in the process of insertion. It is a risk mitigation strategy in patients who have failed anticoagulation or for whom anticoagulation is absolutely contraindicated.