DVT/PE/VTE

Adrian Burger

26 April 2007

Virchow Triad

3 primary components:

• venous stasis

• injury to the intima

• changes in the coagulation properties of the blood

Thrombus

• Originates as a platelet nidus in the region of venous valves located in the veins of the lower extremities.

• Further growth occurs by accretion of platelets and fibrin and progression to red fibrin thrombus, which may either break off and embolize or result in total occlusion of the vein.

Pulmonary Emboli

• From the thrombi originating in the deep venous system of the lower extremities

• Rarely, they may originate in the pelvic, renal, or upper extremity veins and the right heart chambers.

• Large thrombi lodge at the bifurcation of the main pulmonary artery or the lobar branches, accumulate and may cause haemodynamic compromise.

• Smaller thrombi continue distally, occluding smaller vessels in the lung periphery. These are more likely to produce pleuritic chest pain by initiating an inflammatory response adjacent to the parietal pleura.

• Most pulmonary emboli are multiple, and the lower lobes are involved more commonly than the upper lobes

Anatomy

Risk Factors• age - as people over 40 are at greater risk of DVT• a past history of DVT• a family history of DVT• an inherited condition that makes the blood more likely to clot than usual• immobility• obesity • recent surgery or an injury, especially to the hips or knees • pregnancy• having recently had a baby• having cancer and its treatments • taking a contraceptive pill that contains oestrogen - but most modern pills

contain a low-dose, which increases the risk by an amount that is acceptable for most women

• hormone replacement therapy (HRT) - but for many women, the other benefits outweigh the increase in risk of DVT

• treatment for other circulation or heart problems

Why Treat?

The consequences of venous thrombosis:

 • Distal DVT }Symptomatic and Asymptomatic• Proximal DVT

• Symptomatic PE 30%• Asymptomatic PE 40%• Fatal PE • Post-phlebitic syndrome

Wells Criteria

Wells

• Low risk (-2-0) = 3-13%

• Moderate risk (1-2) = 17-38%

• High risk (>2)= 60-75%

• Clinical Intuition = 38% underestimation

Special InvestigationsTest Advantages Disadvantages

Contrast “Gold standard” Invasive

Venography Sensitivity approaches 100% Requires specialized equipment

  Easily interpretable Rare, but serious side effects

Magnetic Resonance Highly accurate Expensive

          Imaging Safe during pregnancy Not readily available

  Non-invasive  

Computed Tomography Non-invasive Limited data

  Can diagnose pelvic DVT  

  Concurrently exclude PE  

Ultrasonography Highly accurate Not accurate for calf or pelvic DVT

  Non-invasive Complete study is time consuming

D-Dimer Rapid laboratory study Only used to rule-out DVT

  Can aide in exclusion of DVT  

15 DVT Studies 8 PE Studies

• High Risk Prevalence 17-85%

• Moderate Risk Prevalence 0-38%

• Low Risk Prevalence 0-13%

• High Risk Prevalence 38-78%

• Moderate Risk Prevalence 16-28%

• Low Risk Prevalence 1-3%

Clinical Decision Rule + D-dimer?

• 15 Studies• Low Probability + Neg D-dimer 0.5% 3 month incidence• Moderate Probability + Neg D-dimer 3.5% 3 month incidence• High Probability + Neg D-dimer 21.4% month incidence

D-dimer Alone

• Review of 5 systematic reviews Latex Turbidimetric and ELISA

• Review of 78 studies ELISA & Quantitative Rapid ELISA

• Cutoff 500ng/ml

• Varies with age and co-morbidity

• Low to Moderate Probability patients

D-dimer Alone

PE• ELISA 95% Sensitivity 45% Specificity

• Turbidimetric Assay 93% Sensitivity 51% Specificity

DVT or PE• ELISA 95% Sensitivity 40% Specificity

• Quant Rapid ELISA 97% Sensitivity 50% Specificity

Ultrasound

• 8 Systematic Reviews Contrast venography as gold standard B-mode US (compression US) Duplex US – with or without colour Doppler

• Symptomatic/Asymptomatic/Both

• Proximal/Distal/Both

US

Ultrasound?

Ultrasound

• Good sensitivity Symptomatic, proximal 93-100% • Good specificity all round 97-100%

• Poor for - asymptomatic 47-62% - upper extremity 56-100% - calf 25-93%

Ultrasound for DVT

• High Sens and Spec for proximal lower extremity

• Low Sens but High Spec for high risk asymptomatic patients

• Poor Sens for Calf Vein

• Follow-up 7 days if symptomatic and first US negative especially if moderate to high risk

CTA for PE?

CTA

• 10 Systematic Reviews Old helical CT scanners PA comparison only in 4 (80-86% Sens) Sensitivities 66-93% Specificities 89-98%

• At best 90% sensitivity compared with PA• Specificity better at 95%

Conclusions

• Clinical Prediction Score Establish pre-test probability

• D-dimer + Clinical Score High negative predictive value No further studies needed if low risk and neg

• D-dimer in isolation ELISA and Rapid quantitative ELISA Young patients, short duration

Conclusion

• Ultrasound Good for symptomatic, proximal lower extremity DVT Poor for asymptomatic, distal, upper extremity

• CTA Newer multislice CT up to 100% sensitive

DVT Algorithm

References

• Ann Intern Med. 2007 Feb 6;146(3):I43. Epub 2007 Jan 29

• Ann Fam Med. 2007 Jan/Feb Vol 5 No 1

• Ann Emerg Med. 2003;42:124-135

• Emerg Med Clin North Am.Vol 22 No 3 Aug 2004