VTE Flashcards
Where do thrombi form
USually at site of valves
How does a Thrombus form
Valves become a site of turbulent flow leading to thrombus formation. Valves can be damaged by trauma, stasis and occlusion
Once formed a thrombus grows by successive adherence of platelets and fibrin
Consequences of thrombus formation in a vein
1) lysis and resolution: if small thrombus resolves (fibrinolytic action)
2) Organisation: scar tissue obliterates lumen and blocks it so blood flows through collateral vessels
3) Recanalisation: leads to scar formation and residual thrombus in lumen
4) embolism: fragmentation of thrombus leads causes embolus to travel to vessel
Consequences of emboli
1) Often numerous small emboli may not affect patient and cause damage gradually, resulting in idiopathic pulmonary hypertension.
2) Larger emboli may cause shortness of breath and chest pain; patient is likely to seek medical attention and these may require treatment or resolve on their own.
3) Long emboli which lodge at bifurcation of pulmonary vessels leading to acute outcome e.g. death
Risk factors for thrombus (Virchow’s triad)
Stasis
Hypercoagulable state
vessel wall injury
What increases risk of hyper coagulable state
Oestrogen therapy (hrt, COC) Pregnancy Sepsis Malignancy Congestive heart disease Factor V Lieden (thrombophilia) Antiphospholipid/lupus anticoagulant
What increases risk of stasis of blood
Age Venous insufficiency or varicose veins Obesity Immobility Continuous travel Hospitalisation
What increases vessel wall injury
Trauma or surgery
Indwelling venous catheters
How to take a history for VTE
HPC
SOCRATES
PMH- prior VTE, inflammatory disease, malignancy, thrombophilia
PSH- recent surgery or hospital admission?
Medications- anything with oestrogen, prior need for anticoagulation
Obstetric history- pregnancy, termination, with in past 6 weeks
family history- and VTE or thrombophilia
Travel history- Travel >3h in past 4 weeks
SH- family, dependents, carers, house, smoking and alcohol,
ICE
Presenting complaint of DVT
Unilateral localised pain (throbbing) in one leg Oedema of leg Calf swelling/oedema Tenderness of lower limb Skin changes (redness, warmth) Distension of legs
Diagnostic tool for suspected DVT
Wells score
What test for suspected DVT
D-dimer
-Measures a degradation product released by lysis of a cross-linked fibrin clot
When is d-dimer useful and not useful
D dimer should not be done In those with a high clinical probability of VTE
A negative d-dimer can exclude patients with a low probability of PE
When would you request a doppler ultrasound
Wells score > or equal to 2, high clinical suspicion or a low Wells score but positive D-dimer
When should d-dimer be used
Useful for excluding patients with a low probability of DVT