Lecture 9: DVT and PE's Flashcards
Which 3 factors of the anticoagulant pathway regulate clot formation by preventing excess thrombin production?
Protein C and S and antithrombin
What are the components of Virchow’s triad?
- Venous stasis
- Endothelial damage
- Hypercoagulability
What is the most common thrombophilic disorder; leads to what?
- Factor V Leiden mutation –> activated protein C resistance
- Results in protein C being unable to inactivate factor V and VIII, which leads to unregulated prothrombin activation
What is a pro and con of using D-dimer in the assessment of DVT/PE?
- Pro = negative test makes DVT unlikely; simple to perform
- Con = positive test is not diagnostic of DVT; other conditions can elevate D-dimer
What is considered the gold standard screening modality for DVT/PE in intermediate cases; what are some pros and cons of using it?
- CT pulmonary angiography (CT angiography)
- Pros: high sensitivity and specificity; accurate anatomy assessment
- Cons: requires contrast (allergies, AKI), expensive, radiation exposure, and may miss small peripheral clots
What are the pros and cons of using ventilation/perfusion scans in the evaluation of DVT/PE?
- Pros: high sensitivity + inexpensive
- Cons: low specificity + may not demonstrate small sub-segmental defects
What is the tx for factor V leiden mutation in pt with no prior episodes vs. prior episodes of thrombosis?
- No prior episodes: just observation; DVT prophylaxis and risk reduction
- Prior episodes: consider lifelong anticoagulation
A mutation in the prothrombin gene at position G20210A causes what?
↑ levels of prothrombin that leads to excess thrombin formation
In a patient whose clot does not respond to heparin therapy, which inherited thrombotic disorder should be suspected; why?
Antithrombin III deficiency; since heparin requires the presence of antithrombin because it enhances the activity of antithrombin
Why is the incidence of DVT of the upper extremities rising in incidence?
Secondary to ↑ use of indwelling venous catheters
The syndrome of DVT includes thrombosis in which 2 areas?
- Proximal leg veins
- Large veins of the upper extremities
If the D-dimer is positive or if the clinical likelihood of DVT is high which imaging modality should be used?
Duplex ultrasonography = excellent sensitivity and specificity
What is the most effective treatment for prevention of VTE in hospitalized pt’s with risk factors?
Pharmacologic prophylaxis
Which agent is used most often for longer-term anticoagulation in pt with established DVT; describe how it’s administered and the guidelines that need to be followed?
- Warfarin
- Typically initiated w/ heparin and both used for minimum 5 days until INR = 2-3 for 2 measurements taken 24 hrs apart
What are some pros and cons of the newer anticoagulant agents, dabigatran, rivaroxaban, apixaban, and edoxaban?
- Oral, rapid onset, do not require monitoring or overlap w/ heparin; minimal interactions with foods and other meds
- Most cannot be used in pt’s w/ significant kidney failure
Once a patient with established DVT is on stable anticoagulation they should be treated for a minimum of how long?
3 months
If there are strong indications to anticoagulant therapy in pt with established DVT what treatment option exists; what are some downfalls to this treatment?
- An inferior vena cava filter should be placed
- Will ↓ likelihood of PE in short-term, but they may actually ↑ the long-term risk of recurrent DVT
In clinically stable pt’s with a low probability of PE, which lab value can effectively rule out PE and is correlated with an excellent outcome without further workup or tx?
Normal D-dimer
What is the indication for using D-dimer in pt’s with a higher probability of PE or clinical instability?
D-dimer testing should not be used to confirm or exclude the diagnosis and further testing is indicated
What are the pros and cons of using doppler venography for DVT/PE evaluation?
- Pro: inexpensive, easy, no radiation, and flow physiology
- Cons: tech. dependent + ↑ false positives/negatives
A totally normal finding using which imaging modality is the only one that can exclude PE?
V/Q scan
What would be the imaging modality of choice to use in a patient with renal failure or someone who is obese for initial assessment of PE?
V/Q scan
When may thrombolytic therapy be effective in patient with PE?
- Pt’s with circulatory shock to PE
- Pt’s with acute embolism and pulmonary HTN or RV dysfunction by without arterial hypotension or shock
A patient with a Wells Criteria score of 0 or lower for DVT should be managed how?
- Should proceed to d-dimer testing
- A (-) high or moderate sensitivity d-dimer –> no further test
- A (+) d-dimer should precede to U/S testing
- If U/S (-) is sufficient to rule out DVT
- If U/S (+) concern for DVT; strongly consider anticoagulant tx
