Thrombosis And Embolism Flashcards
2 types of non laminar blood flow
Turbulent and stagnant
caused by thromboembolism, atheroma, hyperviscosity, spasm, external compression, vasculitis, vascular steal
Virchow’s triad
Changes in blood vessel wall
Changes in blood constituents
Changes in pattern of blood flow
Factors causing thrombosis (formation of a solid mass of blood within the vascular system during life)
Specific changes in Virchow’s triad causing thrombosis
Endothelial injury
Stasis or turbulent blood flow
Hypercoagulability of blood
What direction does thrombus propagate in
Direction of flow
Causes of changes in blood flow
Stasis eg flights
Turbulence eg atheromatous plaque or aortic aneurysm
Common clinical scenarios of thrombosis
DVT, ichaemic limb, MI
Positive outcomes of thrombosis
Resolution
Organisation/recanalization
Negative outcomes of thrombosis
Death
Propagation to embolism
Definition of embolism
Movement of abnormal material in bloodstream and it’s impaction on vessel, blocking the lumen
Mostly dislodged thrombi
Systemic / arterial thromboembolus
Mural thrombus (MI or AF with LAD)
Aortic aneurysm
Atheromatous plaque
Valvular vegetations
Venous thromboembolism
Paradoxical emboli, originate from DVT, most common cause of thromboembolic disease
Travel to pulmonary arterial circulation and may occlude bifurcation (saddle)
Often multiple, over time these cause pulmonary hypertension and right ventricular failure
Consequences of systemic thromboembolus
Travel to wide variety of sites most commonly lower limbs, then brain and organs
Consequences depend on vulnerability of tissues to ischemia, calibre of occluded vessel, collateral circulation
Risk factors for DVT and pulmonary thromboembolism
Cardiac failure, trauma/burns, post op or partum, nephrotic syndrome, disseminated malignancy, oral contraceptives, age, bed rest, obesity, PMH of DVT
Prophylaxis of surgery patients at risk for DVT
Ted’s (stockings), heparin
Fat embolus
After major fractures, brain kidneys and skin affected
Gas Embolus
From decompression sickness (N2 forms as bubbles which lodge in capillaries
Air embolus
Head and neck wounds, surgery, CV lines
Tumour embolus
From spread
Trophoblast embolus
Pregnant women, placenta goes to lungs
Septic embolus
Eg infective endocarditis
Amniotic fluid embolus
Cause of collapse in childbirth
Bone marrow embolus
Fractures or cpr
Foreign body embolus
Intravascular cannulae tips, sutures etc
Rheumatic fever
Disordered immunity
Inflammation in heart and joints sometimes neuro
5-15y
Flitting pains in joints plus skin rashes and fever
Pancarditis in acute phase with heart murmurs
Patients have had a recent sore throat usually A beta haemolytic streptococcus
Damage to heart by Ab and T cell reactions
Aschoff body
Seen in heart in rheumatic fever , a focus of chronic inflammatory cells, necrosis, and activated mq (antischkows cells)
Rheumatic heart disease
Pancarditis in acute can progress to chronic, manifesting as valvular abnormalities
Inflammation of endocardium and left valves results in fibrinoid necrosis of valve cusps/chordae tendinae and vegetations form
Deforming fibrotic valvular disease particulatly mitral , CT may thicken and fuse
Main cause of MS , can cause MR too.
Tissue factor that causes prothrombin to turn into thrombin
X
Tissue factor that causes fibrin to turn into cross linked fibrin
XIII
components of red venous thrombosis
fibrin and RBC
Arterial thrombosis
from rupture of athersclerotic plaque
comes from arteries of left heart chambers
results in ischaemia and infarction
causes ACS, IS, limb claudication/ischaemia
composed of platelets and fibrin (white thrombus)
venous thrombosis
comes from virchows triad especially stasis and hypercoaguability
originates in venous vakves and sinusoids of muscles
results in back pressire
causes DVT and PE
composed of RBC and fibrin (red thrombus)
causes of acquired hypercoaguability
pregnancy
sepsis
cancer
causes of endothelial dysfunction
Hypertension
smoking
hypercholesterol
causes of endothelial damage
indwelling venous catheters
trauma
surgery
examples of VTE
Limb deep vein thrombosis (DVT) Pulmonary embolism (PE)
Visceral venous thrombosis
Intracranial venous thrombosis
Venous Thromboembolism: Epidemiology
DVT: 1 in 1000 pa PE: 1 in 3000 – 5000 pa (chances) Leading cause of direct maternal death in UK Case fatality rate: 1 to 5% Untreated PE: 30% PE in 20% of autopsies young women more then old men more
Risk factors for VTE
surgery late pregnancy caesatian Lower limb problems eg fracture and vv malignancy reduced mobility Congestive HD HT OC COPD hormone replacement therapy neurological disability thrombotic disorders long distance travel obesity
Symptoms and signs of DVT
Unilateral limb swelling
Persisting discomfort
Calf tenderness
[Warmth]
[Redness- erythema]
[Prominent collateral veins]
[Unilateral pitting oedema]
May be clinically silent
Potential long-term consequence of DVT
Post Thrombotic Syndrome
Damage to venous valves
Incidence of 20-60% within 2 years of DVT
Swelling
Discomfort
Pigmentation
Ulceration in severe form
how is DVT diagnised
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
wells score for DVT (high is over 2)
Active cancer, or cancer that’s been treated within last six months 1
Paralyzed leg 1
Recently bedridden for more than three days or had major surgery within last four weeks 1
Tenderness near a deep vein 1
Swollen leg 1
Swollen calf with diameter that’s more than 3 centimeters larger than the other calf’s 1
Pitting edema in one leg 1
Large veins in your legs that aren’t varicose veins 1
Previously diagnosed with DVT 1
Other diagnosis more likely -2
What is a ‘D-Dimer’?
Breakdown product of cross-linked fibrin
Produced during fibrinolysis
High sensitivity for VTE
Low specificity for VTE
Trauma, malignancy, sepsis, bleeding, cancer, recent surgery
Symptoms and signs of PE
Pleuritic chest pain Breathlessness- dyspnoea [Blood in sputum- haemoptysis] Rapid heart rate- tachycardia Pleural rub on auscultation usually due to pulmonary infarction
Symptoms and signs of massive pulmonary embolism
Severe dyspnoea of sudden onset Collapse Blue lips and tongue - cyanosis Tachycardia Low blood pressure Raised jugular venous pressure May cause sudden death
Diagnosis of pulmonary embolism
Clinical assessment and pretest probability score (Wells score or Geneva score)
Blood test: D-dimer if low pre test probability score
Imaging: if D-dimer positive or high pre test probability score
Isotope ventilation/perfusion scan
CT pulmonary angiogram
Wells score for PE (high is over 4.5)
clinical signs and symptoms of DVT = 3
an alternative diagnosis is less likely than PE = 3
heart rate more than 100 = 1.5
immobilisation for 3 or more consecutive days or surgery in the previous 4 weeks = 1.5
previous objectively diagnosed PE or DVT = 1.5
haemoptysis = 1
malignancy (on treatment, treatment in last 6 months or palliative) = 1
Questions to ask in patients with diagnosed VTE
Was there a clear cause or precipitant?
Recent surgery / hospitalisation
Any symptoms or signs to suggest underlying malignancy?
Consider risk of recurrence
Clinical Risk
Cancer patients
DASH score/ HERDoo2 etc
anticoagulation treatment options for VTE
Anticoagulation is main treatment
Provoked – 3/12
Unprovoked and high risk of recurrence- Lifelong
Parenteral- low molecular weight heparin, a factor 10a inhibitor eg dalteparin, no monitoring but cant use in sig. renal failure
direct oral anticoagulants- 10a inhibitors eg rivaroxaban or direct thrombin inhibitor eg dabigatran, no monitoring but be careful with high BMI and low renal function
treatment for PE and DVT other than anticoagulants
Vascular surgical interventions in massive DVTs
Thrombolysis reserved for massive PE (Collapse, haemodynamic compromise ie. Shocked Patient)
E.g. Alteplase
Aims of treatment of VTE
Prevent clot extension
Prevent clot embolisation
Prevent recurrent clot
Potential long-term consequence of DVT
Post Thrombotic Syndrome
Damage to venous valves
Incidence of 20-60% within 2 years of DVT
Swelling
Discomfort
Pigmentation
Ulceration in severe form
Potential long-term consequence of pulmonary embolism
Most recover fully
Pulmonary arterial hypertension
Serious outcome
4% patients (< 1/20)
