deep venous thrombosis and pulmonary embolism Flashcards
what is a thrombus?
a pathological clot
what are the three things a clot is made up of?
fibrin
platelets
RBCs
(different ratios for different types of clot)
describe the pathway for the formation of a clot in an artery?
- damage to endothelium
- tissue factor produced
- prothrombin converted to thrombin
- thrombin converts fibrinogen into fibrin
- firbrin foms corss-linked fibrin
- along with platelets to form a white thrombus
what kind of clots thombi form in arteries?
white thrombi, contain few RBCs
what kind of thrombus forms in veins?
red thrombus
describe the formation of a red thrombus
- tissue factor and the contact pathway cause the production of thrombin
- thrombin converts fibrinogen into fibrin
- fibrin traps RBCs forming a red thrombus
what is the most common cause of white (arterial) thrombus?
rupture of atherosclerotic plaque
what are the locations of arterial thrombi?
arteries and left heart chambers
what are the consequences of arterial thrombi?
ischaemia and infarction
what are the disease caused by arterial thrombi?
ACS
ischaemic stroke
limb claudication and ischaemia
what is the composition of an arterial thrombus?
white thrombus- platelets and fibrin
what is the mechanism for the formation of venous thrombi?
combination of Virchow’s triad especially stasis and hypercoagulability
what is the location of origin of venous thrombi?
venous valves and venous sinusoids of muscle
what is Virchow’s triad?
stasis
hypercoagulability
endothelial damage/dysfuntion
what do venous thrombi result in?
back pressure
what are the diseases caused by venous thrombosis?
DVT
pulmonary embolism
what is the composition of a venous clot?
red thrombus- RBCs and fibrin
what can cause stasis (in Virchow’s triad)
immobility
long haul travel
what can cause vessel damage/dydfunction in Virchow’s triad?
dysfunction: hypertension smoking hypercholesterolaemia damage: -indwelling venous catheters -trauma -surgery
what can cause hypercoagulabilty (in Virchow’s triad)?
-inherited causes
-acquired:
pregnancy
cancer
sepsis
what is an embolism?
intravascular material that migrates from its original location to a distal vessel
what is thromboembolism?
movement of blood clot along a vessel
give 4 examples of venous thromboembolism?
limb DVT
pulmonary embolism
visceral venous thrombosis
intracranial venous thrombosis
what are the symptoms of DVT?
unilateral limb swelling
persisting discomfort
calf tenderness
what are the signs of DVT?
warmth
redness
prominent collateral veins
unilateral pitting oedema
or may be clinically silent
when may DVT cause bilateral signs and symptoms?
when there is obstruction of the IVC
what are the long-term consequences of DVT?
post thrombotic syndrome causing damage to venous valves. This causes: swelling discomfort pigmentation ulceration of veins in severe form
how is DVT diagnosed?
- clinical assessment and pretest probability score (Wells score)
- Blood test: D-dimer if low pre-test probability score
- imaging compression ultrasound if positive D-dimer or high pre-test probability score
what is D-dimer test, in terms of sensitivity and specificity?
-high sensitivity for VTE
-low specificity for VTE
as positive in:
trauma
malignancy
sepsis
bleeding
cancer
recent surgery
what are the symptoms of PE?
pleuritic chest pain
dysmpnoea
haemoptysis
what are the signs of PE?
tachycardia
pleural rub in ausculatation (due to pulmonary infarction)
what are the symptoms of massive pulmonary embolism
severe, sudden dyspnoea
collapse
what are the signs of massive pulmonary embolism?
cyanosis (blue lips and tongue) tachycardia hypotension raised JVP may cause sudden death
how is PE diagnosed?
- clinical assessment and pretest probability score (Wells or Geneva)
- D-dimer test if low pretest probability score
- imaging if D-dimer positive or high pre test probability score
- isotope ventilation/perfusion scan
- CT pulmonary angiogram
what are the potential long-term consequences of pulmonary embolism?
- most recover fully
- pulmonary arterial hypertension
what are the aims of treatment of VTE?
prevent clot extension
prevent clot embolism
prevent recurrent clot
what are anticoagulation treatments for VTE?
parental options: -unfractioned heparin -low molecular weigth heparin Enteral options: -Warfarin -direct oral anticoagulants (DOACs)
Thrombolysis reserved for massive PE
eg. alteplase
what are the prevention methods for VTE in hospital?
- early mobilsation
- anti-embolism stockings
- other mechanical methods of thromboprophylaxis
- pharmacological thromboprophylaxis
why is pulmonary infarction rare in PE?
dual vascular supply to lungs with anastomoses;
Pulmonary vascular system
Bronchial vascular system
what causes infarction in PE?
- blockage in branch of pulmonary artery
- leads to increase in pressure within pulmonary vasculature
- force within bronchial artery may be insufficient to overcome this
- leakage of blood into alveolar space occurs and leads to infarcion.
