Deep vein thrombosis

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Contents

Introduction

Also known as DVT, deep venous thrombosis

Deep vein thrombosis is a manifestation of venous thromboembolic disease (VTE) of which the most serious consequence is pulmonary embolus - a major cause of death and one which is persistently under-suspected and under-prevented. Significant morbidity also results from post-thrombotic syndrome.

It is nowadays widely noted to be a major and somewhat avoidable risk after elective surgery. However as it is so common in inpatients most guidelines recommend a routine risk assessment upon admission, both to guide prophylaxis, but more importantly to remind clinical staff to consider the issue.

Diagnosis

By history, examination and special investigation. A high index of suspicion saves lives.

History

Pain in the leg. Particularly following likely predisposing factors such as immobility (operation, travel) systemic inflammation (operation, illness). Ask about previous episodes, IV drug abuse (normally clinically apparent), recurrent miscarriage and family history.

Examination

Unilateral swelling in calf with or without tenderness in the line of the major veins. Diversion of blood flow into superficial veins.

Risk assessment

A medical algorithm exists - the Modified Wells Score - to assist people in deciding whether to perform ultrasound investigation of the lower limb veins in addition to D-dimer estimation in deciding whether to treat as DVT. Do note that the ultrasound examination used determines what you will find (and treat!). So if you use compression ultrasound (CUS) of proximal veins you need to repeat this in one week if negative. Complete compression ultrasound (CCUS) if used exactly according to protocol has very similar results to venography.[1]

Modified Wells Score calculator

The most cost effective strategy in UK practice, is usually based on a combination of Wells score, D-dimer and ultrasound (with repeat if negative)[2].

There are some interesting risk factors. For example, while dehydration is a risk factor, over-hydration of supine patients (such as the bedridden or those having surgery) causes distension of the deep veins and actually increases radiofibrinogen detectable DVT[3].

Special investigations

  • D-dimer blood level.[4][5]
    • D-dimer tests are not equivalent, but choice can be based on a fair evidence base. Quality control has also proved problematical in community orientated diagnosis. Negative quantitative ELISA and some automated turbidimetric assays should be part of diagnostic algorithms to identify those of low risk of DVT (complications). D-dimer is less useful in hospitalised patients and those with high clinical probability. D-dimer is raised by so many causes that a positive D-dimer has an almost useless specificity and sensitivity.
  • Compression ultrasonography of leg and pelvic veins.
    • There are three different techniques and this means that independent of operator variability there is considerable potential for confusion in interpretation of the literature. Each technique has to be tied to a specific evidence based treatment algorithm and the choice of algorithm is a trade off between clinical effectiveness and resources. If your local guideline requires treatment of some (or all) distal DVTs you only have one option (complete compression ultrasonography)
      1. Restriction to proximal calf veins and if negative repeat in 1 week
      2. Assess both proximal and distal leg veins (complete compression ultrasonography). Some guidelines require repeating at 1 week depending upon clinical risk score
      3. Single proximal compression ultrasonography which if negative in those with high clinical probability score needs supplementation with further diagnostic imaging to have similar 3 month risk of VTE to complete compression ultrasonography
  • Xray phlebography with contrast medium (gold standard but less-used now, and not free of hazard).


Treatment of DVT

Anticoagulation is the main treatment and is also used in thromboprophylaxis. There is consensus that proven proximal DVT should be anticoagulated. There is a strong evidence base for various scenarios and for several agents such as warfarin and rivaroxaban. It is suggested that if local evidence based guidelines exist they should be used.

Distal lower limb DVT

International guidelines differ and recently the main American guidelines changed to not recommend treatment for isolated asymptomatic distal calf DVT[6]. However many regard this as problematic as evidence exists of proximal propagation in up to 15%. The latest studies suggest patients who have had orthopedic procedures, those with malignancy, and those that were immobile have a higher incidence of clot propagation and so these patients have been recommended to have full anticoagulation until the patient is ambulatory or a follow-up duplex scan is negative[7]. But we do not know how to subgroup risk, as no high quality trials have yet addressed this issue using modern techniques for diagnosis and follow-up so either treatment or no treatment is of unknown effectiveness[8]
LogoKeyPointsBox.pngThe superficial femoral vein is a proximal deep vein so treat thrombosis in it even if your unit does not diagnose and therefore treat distal DVT !
Proximal extension with pulmonary embolism certainly occurs with distal DVT, and the decision not to treat in those with risk factors for VTE is suspected to be more likely to have medico-legal implications.

Metaanalysis suggests that in patients where anticoagulation was withheld:

  • Studies using compression ultrasound (CUS) of proximal veins (Proximal DVT) as criteria for diagnosis had 3-month thromboembolic rate of 0.6% (95% CI: 0.4-0.9%)
  • proximal and distal (complete) compression ultrasound (CCUS) (All DVTs) as criteria for diagnosis had 3-month thromboembolic rate of 0.4% (95% CI: 0.1-0.6%) with 50% of these confined to distal veins !

Searching for distal DVT doubles the number of patients given anticoagulant therapy and and a distal DVT has about a sixth the risk of pulmonary embolism from these figures.[8]

Prevention of DVT

See external links below

External links

References

  1. Schellong SM. Complete compression ultrasound for the diagnosis of venous thromboembolism. Curr Opin Pulm Med. 2004;10(5):350-5
  2. Goodacre S, Sampson F, Stevenson M, Wailoo A, Sutton A, Thomas S, et al. Measurement of the clinical and cost-effectiveness of non-invasive diagnostic testing strategies for deep vein thrombosis. Health technology assessment (Winchester, England) 2006;10:1-168, iii-iv.
  3. Comerota AJ, Stewart GJ, Alburger PD, Smalley K, White JV. Operative venodilation: a previously unsuspected factor in the cause of postoperative deep vein thrombosis. Surgery. 1989 Aug; 106(2):301-8: discussion 308-9.
  4. Wells, Philip S., Anderson, David R., Rodger, Marc, Forgie, Melissa, Kearon, Clive, Dreyer, Jonathan, Kovacs, George, Mitchell, Michael, Lewandowski, Bernard, Kovacs, Michael J. Evaluation of D-Dimer in the Diagnosis of Suspected Deep-Vein Thrombosis. N Engl J Med 2003 349: 1227-1235
  5. D-dimer: the test. Labtestsonline web site. Last viewed 14 June 2007.
  6. Kearon C, Akl EA, Comerota AJ, Prandoni P, Bounameaux H, Goldhaber SZ, Nelson ME, Wells PS, Gould MK, Dentali F, Crowther M, Kahn SR. Antithrombotic therapy for VTE disease: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012 Feb; 141(2 Suppl):e419S-94S.(Link to article – subscription may be required.)
  7. Singh K, Yakoub D, Giangola P, DeCicca M, Patel CA, Marzouk F, Giangola G. Early follow-up and treatment recommendations for isolated calf deep venous thrombosis. Journal of vascular surgery : official publication, the Society for Vascular Surgery and. International Society for Cardiovascular Surgery, North American Chapter. 2012 Jan; 55(1):136-40.(Link to article – subscription may be required.)
  8. a b Righini M, Paris S, Le Gal G, Laroche JP, Perrier A, Bounameaux H. Clinical relevance of distal deep vein thrombosis. Review of literature data. Thromb Haemost. 2006;95(1):56-64