DVT/PE/VTE Adrian Burger 26 April 2007. Virchow Triad 3 primary components: venous stasis injury to...
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Transcript of DVT/PE/VTE Adrian Burger 26 April 2007. Virchow Triad 3 primary components: venous stasis injury to...
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DVT/PE/VTE
Adrian Burger
26 April 2007
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Virchow Triad
3 primary components:
• venous stasis
• injury to the intima
• changes in the coagulation properties of the blood
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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.
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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
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Anatomy
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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
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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
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Wells Criteria
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Wells
• Low risk (-2-0) = 3-13%
• Moderate risk (1-2) = 17-38%
• High risk (>2)= 60-75%
• Clinical Intuition = 38% underestimation
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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
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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%
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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
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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
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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
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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
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US
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Ultrasound?
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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%
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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
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CTA for PE?
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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%
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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
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Conclusion
• Ultrasound Good for symptomatic, proximal lower extremity DVT Poor for asymptomatic, distal, upper extremity
• CTA Newer multislice CT up to 100% sensitive
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DVT Algorithm
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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