Acute Venous Pathophysiology Flashcards
What type of pressure and flow does a venous system have?
Low pressure and spontaneous flow- shows changes with respiration and augmentation
When might a DVT occur?
When there is alteration of normal Hemodynamics or architecture of the venous system
Who presented his concepts on the causes of a DVT? When?
Rudolph Virchow in 1856
What is the Virchow triangle?
3 established factors known to cause DVTs
What is included in the Virchows triangle?
Stasis
Hypercoagulability
Intimal injury
What is the most common factor to cause a DVT?
Venous stasis
What are some factors that can cause venous stasis? (9)
Immobility MI CHF COPD Obesity Pregnancy (L>R) Previous DVTk Surgery Paraplegia
What are some examples of hypercoagulability states? (4)
Pregnancy
Cancer
Estrogen intake (BCP)
Genetic blood factors
What are some indications for LE vascular US?
Suspicion of DVT Suspicion of PE Incompetent valves and mass causing pain and swelling Edema/swelling Limb pain/tenderness Ulceration Discolouration in the gaiter area Varicose veins Hypercoagulable state Pallor Cyanosis Positive d-dimer test result
What are the symptoms of a PE?
SOB
Chest pain
Hemoptysis
What is the most common mass/cyst?
Bakers cyst
Where are ulceration found and what is their appearance?
Gaiter area (medial malleolus) Shallow and round
What disease is suspected with a pallor coloured leg?
Phlegmasia alba dolens
What disease is suspected with a cyanotic leg?
Phlegmasia cerulean dolens
What are indications for an UE venous US?
Suspicion of DVT History of catheter lines or drug abuse Head and neck swelling/edema Limb redness Suspected injury after venous puncture/catheterization, esp in IJV Symptoms of a PE
What might a pts history include when a acute DVT is suspected?
Acute onset of leg pain and swelling Persistent leg/calf swelling Redness/erythema Warm skin Symptoms of a PE Previous DVT Clotting issues (including problems regulating anticoagulation therapy and malignant cancer)
Is persistent leg/calf swelling unilateral or bilateral?
Usually unilateral but can be bilateral
Where does thrombus formation usually begin?
Soleal sinus/calf veins or at the valve cusps
What is predominately the main reason for thrombus formation?
Stasis
What occurs during early thrombus formation? Why?
Aggregations of RBCs near valve cusps due to stasis and eddy currents
What does fibrin do? What does it cause?
Stabilizes RBCs against endothelium and propagation occurs
What causes enlarged pockets to be formed between the clot and vein wall?
Combination of fibrinlysis, thrombus reaction and fragmentation
What is the most common outcome for the venous lumen?
Restored venous lumen with intimal thickening
Residual fibrous synechia (scarring or formation) is present in what % of pts?
10%
What is considered and acute DVT?
Days to 1-2 weeks old and consistent with the timing of clinical symptoms
What does a recent clot appear as compared to the surrounding tissue?
Anechoic to low echogenicity
What happens to the clots echogenicity as it ages?
Increases slightly
What 2 things will confirm thrombus formation?
Dilation of the vein and lack of compressibility
What is the primary diagnostic modality for detection of a lower extremity DVT?
Duplex sonography
Why is duplex scanning the primary diagnostic modality for detection of a LE DVT?
Due to the few limitations and high accuracy rate
What are some common origins for development of a thrombus?
Muscular veins Valve sites Venous confluence Deep venous system Superficial venous system Perforators
What is the sonographic findings of an acute DVT?
Vein often enlarged with isoechoic or slightly echogenic material seen distending in vein
Will the acute DVT be compressible?
The veins will not coapt
What determines the degree of obstruction and extent of DVT?
Color Doppler
What will the proximal end of the clot appear to do if it is not attached to the vein wall?
“Float” or “wave”
What is collateralization?
Accessory vessels that re-route flow around an obstruction
When does collateralization occur? Can it be seen on US?
Occur readily in the presence of a DVT and can be seen on US
How are incompetent valves diagnosed?
Demonstrate reverse flow in response to valsalva or compression proximal to the site of the valve
Is continuous venous flow, without respiratory phasicity normal?
No it is abnormal
What does continuous venous flow, without respiratory phasicity suggest?
Proximal disease
See page 5
What is a sub-acute thrombus?
Thrombus 1-2 months old
How does the sonographic appearance change with a sub-acute thrombus?
Increasing echogenicity and decreasing vein diameter with losing of clot
What is recanalization?
Some resumption through the clot
In what type of thrombus can recanalization occur?
Sub-acute thrombus with formation of collaterals
What is chronic thrombus scarring?
The result of venous thrombosis that occurred months to years after the initial date
What does the fibrous tissue that remained from a chronic thrombus appear like?
Moderate to high echogenicity and may be isoechoic to surrounding tissue making it difficult to access
What are chronic thrombosis difficult to assess?
May appear isoechoic to surrounding tissues
What are the sonographic findings of a chronic DVT? (4)
Echogenic thrombus
Vein smaller then artery
Presence of collaterals
Recannalization
See page 9
What is the normal criteria for venous duplex exam? (5)
- Complete coaption with little pressure
- Absent intraluminal echos
- Color flow fills lumen
- Normal Doppler spontaneity, phasicity and augmentation
What is the abnormal criteria for a venous duplex exam? (5)
- Lack of complete vein compression
- Intraluminal echos present
- Decrease or absence of color flow
- Abnormal Doppler spontaneity, phacisity and augmentation
What are ACUTE thrombus descriptions & Characteristics? (4)
- Light to medium echogenic or anechoic
- Spongy texture on compression (homogeneous)
- Poorly attached or free floating
- Dilated vein (if not completely occluded)
What are CHRONIC thrombus descriptions & Characteristics? (5)
- Bright heterogenous echos
- Irregular texture (heterogenous)
- Attached
- Same size as artery or vein is contracted
- Collateral veins may be seen
Can veins be completely or partially compressible in both acute and chronic stages?
Yes combination of events can occur
What is a chronic thrombus with partial recanalization seen as?
Small color flow channels within the thrombus
Is the age of the clot always detectable?
No sometimes indeterminate
Where is the most common site for a calf vein DVT?
Soleal sinus - clinical importance still unknown - propagation into popliteal varies widely
What are the current approaches to treat a calf vein DVT? (2)
- Surveillance with duplex US to check for propagation to larger veins
- Therapeutic anticoagulation for 6 weeks
What other thrombus management is similar to that of a iliac DVT?
Femoropopliteal thrombus
What DVT is difficult to image with US?
Iliac DVT
How is a iliac DVT examined?
Indirect assessment with Doppler signal
How is an iliac DVT diagnosed?
Venography
What is Mary-Thunder syndrome?
Compression of the Lt CIV b/w CIA and spine
What vessels are compared to rule out iliac obstruction?
Bilateral CFV waveforms compared
See page 13
What causes an increase of DVTs in the UE?
Use of central venous catheters
What can predispose an axillosubclavian vein thrombus formation?
Previous radiation treatment
Pt hx of mediastinal lymphoma
Trauma or surgery to area
Thrombosis is the disease mechanism…T/F
True
Are superficial or deep thrombosis more common? Is it potentially fatal?
Deep DVTs more common and potentially fatal
What % of PE originate from the LE?
90%
What % of pts who have had a DVT develop chronic venous insufficiency?
60%
Can a calf vein cause a DVT? Can it be fatal? Why?
A calf vein can cause a DVT but to small to be fatal
What are the medical treatments for an acute DVT? (3)
- Anticoagulation
- Thrombolytic agent
- Control the risk factors
What is anticoagulation?
Therapy for 3-6months (heparin/warfarin) prevents clot propagation
Does anticoagulation dissolve the thrombus?
No
What is considered the standard medical treatment for an acute DVT?
Anticoagulation
What is a thrombolytic agent?
A thrombolytic agent (streptokinase) may be injected into the UE to dissolve a thrombus
What helps to control the risk factors to promote venous return in the case of an acute DVT?
Limiting long periods of activity
Wearing support hoses
Elevating legs
Checking for hypercoagulabilty states ad factors in the blood
What are the surgical treatments for an acute DVT? (3)
- IVC filter
- Venous thrombectomy
- Bypass grafting
When is an IVC filter used as a treatment for an acute DVT?
In pts who cannot be anticoagulated
When is bypass grafting considered?
Caval occulsion
What are the endovascular treatments for a acute DVT? (3)
- Catheter directed thrombolysis
- Balloon venoplasty and stenting
- Mechanical thrombectomy
What thrombolysis is used for an acute DVT?
Urokinase
What vein is balloon venoplasty and stenting most often used?
Chronic iliofemoral DVT
What is an example of mechanical thrombectomy?
Angiojet
What is phlegmasia Alba Dolens?
Decreased venous drainage due to thrombosis of the extremity deep veins without collateral vein involvement
What color may the pts leg look like with phlegmasia Alba Dolens?
White
What causes the white coloured appearance in phlegmasia Alba Dolens?
Extensive edema obscures circulation
What is an contributing factor in phlegmasia Alba Dolens?
Arterial spasms
What can phlegmasia Alba Dolens progress into?
Phelgmasia cerulea dolens
What is Phelgmasia cerulea dolens?
Massive venous occlusion due to multi segment thrombosis of extremity deep veins; iliofemoral, lower leg veins and their collaterals
What causes Phelgmasia cerulea dolens?
Massive obstruction of venous outflow reduces arterial inflow causing arterial vasoconstriction and potentially arteriolar thrombosis
What causes the discolouration of the skin in Phelgmasia cerulea dolens? What color does it turn?
Venous congestion resulting from significant iliac vein thrombosis causes a blue color
What are some signs of Phelgmasia cerulea dolens?
Massive thigh and leg swelling
Acute onset of Phelgmasia cerulea dolens leads to what?
Starts with hypoxia and leads to gangrene
Is Phelgmasia cerulea dolens a surgical emergency?
Yes
What is May-Thurner syndrome?
Compression of the left CIV by the right CIA and spine (5th lumbar vertebrae), increasing the risk for DVT
What can May-Thurner syndrome result in?
Left CIV stenosis and left leg swelling
What is Paget-Schroetter syndrome?
Most common form of axillosubclavian thrombosis in ambulatory healthy people
What is another name for phelgmasia cerulea dolens
Effort thrombosis
Are men or woman most effect by the Paget-Schroetter syndrome?
Men
What is Paget-Schroetter syndrome caused by?
Anatomical variations of muscle and bone in the thoracic inlet
When does the Paget-Schroetter syndrome occur?
When there is thrombosis of the axillary/subclavian vein at the thoracic inlet (b/w muscle/bone)
What is thrombophlebitis (superficial)?
Inflammation with thrombus formation
How is thrombophlebitis diagnosed?
Diagnosed clinically- “hard cord”
US used to delineate extent of thrombus, particularly at major confluences into the deep system
Approximately what % of superficial thrombosis has a recurrent DVT?
20%
What is the treatment for thrombophlebitis?
Ambulation and compression therapy along with anti-inflammatory drug admission
How does congestive heart failure affect pulsatility?
Increases pulsatility
Congestive heart failure results in what? Why?
Bilateral lower extremity edema from hydrostatic pressure
What is a hematoma?
Accumulation of blood within tissue
Why is a hematoma difficult to distinguish from the effects of a DVT?
They cause pain and swelling similar to that of a DVT
How do extremity soft tissue hematoma occur?
Trauma, anticoagulation therapy or vigorous exercise
What does a hematoma appear as on US?
Hypoechoic mass with ill defined border, contained within muscles or tissues
What occurs to the hematoma sonographically with time?
Will become more echogenic and heterogeneous
What occurs to the blood in the hematoma once it lysis?
May appear once again anechoic in the final stages
What may a large hematoma do to surrounding veins?
Compress the vein causing venous distension and sluggish flow
What causes an abscess & cellulitis?
Bacterial infection
What is an abscess?
Enclosed collection of pus
What is cellulitis?
Diffuse collection of fluid within subcutaneous tissue
What can abscess and cellulitis cause?
Swelling, erythema, pain and tenderness
What can the signs and symptoms of a abscess/cellulitis resemble?
Venous thrombosis
Why is US for abscess and cellulitis?
Used to confirm that the venous system is patent
Refer to page 18
What is a Bakers cyst?
Dilation of bursae (sac of synovial fluid) that communicates with the knee joint
What types of pts are bakers cysts most common in?
Pts with degenerative joint dx and rheumatoid arthritis
Why do bakers cysts cause pain, tenderness and swelling?
As the cysts enlarge they extend into the muscle planes
Where are the bakers cyst commonly located?
Medial aspect of the knee joint
Crescent shape at the upper end of the knee jt with further extension going inferior into the calf
What is the sonographic appearance of a bakers cyst?
Anechoic but may contain debris and have septations
How should the bakers cyst appear with color Doppler?
No flow within them
What happens when the cysts rupture and track between the tissues into the calf?
Exacerbate the symptoms that mimic DVT and causing severe pain
How do you rule out a hematoma?
By demonstrating communication with the jt space
Describe potential tumors found within the legs
Malignant or benign
Solid with areas of necrosis
May resemble other benign pathologies so its important to demonstrate blood flow in the solid portions
Describe enlarged lymph nodes (adenopathy)
Can be mistaken for thrombosed vein
May cause leg swelling, compression of veins
What is Lymphedema?
Chronic leg swelling due to failure of lymphatic drainage system
Where is lymphedema most common?
Calf and upper extremity
2/3 of cases are unilateral
What is the US appearance of lymphedema?
Thickened subcutaneous tissue which degrades the 2D image
“Ant farm” appearance
Are deep or superficial veins more difficult to assess with lymphedema?
Deep veins
When should a popliteal aneurysm be suspected?
When a pt presents with a lump (swelling) or pain behind the knee
What information does color flow provide within a popliteal aneurysm?
Color flow would be seen within the aneurysm providing it is patent
What are other medical tests to aid in diagnosing thrombosis?
Venography Pulmonary angiogram VQ scan (ventilation Quotient)/ lung scan Isotope venography D-dimer assay
What is a venogram?
Contrast injected into the small veins of the foot and X-rays taken of the whole leg
Ascending for acute disease
Descending for valve disorders
Why is a venogram considered the gold standard exam?
The accuracy of other studies is compared to the venogram
