DVT and PE Flashcards
What is a DVT?
Formation of thrombi within the lumen of the vessels making up the deep venous system - predominantly in venous valve pockets and other sites of presumed stasis
Types of DVT?
Distal Vein Thrombosis - DVT of the calves
Proximal Vein thrombosis - DVT of popliteal vein or of femoral vein (closer to the heart)
What is a PE?
Thromboemboli detach and travel through the right side of the heart to block lung vessels
Virchow’s triad and causes of 3 reasons?
Endothelial injury: Venous disorders Venous valvular disease Trauma/surgery In-dwelling catheters
Circulatory stasis: Left ventricular dysfunction Immobility or paralysis Venous insufficiency or varicose veins Venous obstruction from tumour, obesity or pregnancy
Hyper-coagulable states: Malignancy Pregnancy and peripartum periods Oestrogen therapy (HRT or contraceptive pill) Inflammatory Bowel Disease Sepsis Thrombophilia
Significance of Virchow’s triad?
All predispose to thrombus formation
Exposing risk factors for venous thrombo-embolic disease), i.e: acute conditions or previous happenings?
Surgery Trauma Acute medical illness Acute heart failure Acute resp failure Central venous catheterisation
Predisposing risk factors (patient characteristics)?
History of VTE (biggest risk of clot is having had one before) Chronic heart failure Advanced age Varicose veins Obesity Immobility or paresis Myeloproliferative disorders Pregnancy/peripartum period Inherited or acquired thrombophilia Hormone therapies Renal insufficiency
Inherited disorders that increase VTE risk?
Protein C or Protein S deficiency
Factor V Leiden mutation
Only increase risk by a small amount
Difference between provoked and unprovoked VTE?
Provoked VTE:
Transient/reversible factors, e.g: surgery or hospitalisation
Continuing/irreversible factors, e.g: cancer
Unprovoked (idiopathic) cause - no identifiable cause
Known consequences of VTE?
Fatal PE Risk of recurrent VTE Post-thrombotic syndrome (PTS) Chronic Thrombo-Embolic Pulmonary Hypertension (CTEPH) Reduced quality of life
What is post-thrombotic syndrome?
Chronic venous disease following DVT treatment
Valves no longer function so there is chronic pooling of blood
Also, valvular reflux leads to venous hypertension
Frequency of PTS?
Occurs in nearly 1/3rd of patients within 5 years after idiopathic DVT
Characteristic of PTS?
Pain Oedema Hyperpigmentation - iron deposition leads to staining of skin (hemosiderin deposition) Eczema Varicose collateral veins Venous ulceration
What is chronic thromboembolic pulmonary hypertension (CTEPH)?
Serious PE complication
Original embolic material is replaced with fibrous tissue into the intima and media of pulmonary arteries - pulmonary resistance and right-sided heart failure
Characteristics of CTEPH?
Initial phase - often asymptomatic
Followed by progressive dyspnoea and hypoxaemia
Investigations for DVT?
Pre-test probability scores:
D-dimer - reasonable test of exclusion (use with caution in patients with previous DVT)
Ultrasound - compressibility vs Doppler ultrasound
What is D-dimer?
Breakdown product of cross-linked fibrin
High -ve predictive value for VTE and low +ve predictive value for VTA
Uses of D-dimer?
Valuable first line screening test for suspected VTE with low Wells score
But non-specific (D-dimer is raised in many conditions)
Interpreting the Wells score?
If low probability, check D-dimer (if -ve, no imaging required)
Moderate/high probability - need imaging regardless of D-dimer (-ve imaging and +ve D-dimer requires repeat imaging)
What does Wells score indicate?
PE
What is Geneva score used for?
Low risk - if D-dimer is negative, may not need investigation
Intermediate risk - if D-dimer negative, consider stopping investigation (likely, need investigation to exclude)
High risk - regardless of D-dimer will need imaging
Other imaging techniques for PE?
CXR - usually normal in PE (can show pleural effusions and occasionally infarct)
V/Q scan - mismatched perfusion defects PE; still useful in small, peripheral PEs and pregnancy but is limited by frequency of inconclusive results
CTPA is “gold standard” (but no good for peripheral pulmonary vessels)
Pharmacological and mechanical interventions for DVT and PE?
Pharmacological interventions:
Anti-coagulation
Thrombolysis
Analgesia
Mechanical interventions:
Graduation compression stockings
IVC filters
Treatment of provoked VTE, to prevent recurrence?
Provoked VTA - LMWH for at least 5 days or until INR is greater than or equal to 2, for 24 hours (whichever is longer)
Vitamin-K antagonist (warfarin) within 24 hours and cont. for 3 months
