Clinical Case Studies - DVT/PE

Question 1

What is a DVT?

Answer 1

A clot that usually develops in one of the deep veins. Often occurs in the leg.

• Clot happens in stationary blood
• THROMBUS happens in flowing blood

Question 2

Describe the pathophysiology of a DVT

Answer 2

Virchow’s Triad

• Hypercoagulability - Malignancy, surgery, trauma, OCP, clotting abnormalities
• Venous stasis - Immobility, pregnancy, heart failure
• Trauma - Inflammation, previous thrombosis, atheroma

Question 3

How do platelets function in the context of a thrombus?

Answer 3

• Adhesion to vessel wall
• von willebrand factor (factor VIII) cause shape change and degranulation
• Aggregation and contraction
• Release of prostaglandins, serotonin, thromboxane - effect on vessel walls and tissue cells

Question 4

What are the signs and symptoms of a DVT?

Answer 4

• Asymptomatic
• Pain
• Oedema
• Erythema/Discoloration
• Increased temperature of site
• Engorgement of surface veins

Question 5

How would you investigate for a DVT?

Answer 5

• D-dimer - sensitive but not specific
• B-mode venous compression ultrasonography
• Modified Wells Score

Question 6

What is a PE?

Answer 6

An occlusion of the pulmonary vasculature by a clot.

Often occurs from a deep vein thrombosis that has become dislodged and forms an embolus that lodges in the pulmonary arterial vasculature, blocking the vessels

Question 7

What are the causes of a PE?

Answer 7

• DVT
• Air embolus
• Fat embolus
• Amniotic fluid embolus
• Foreign material introduced via IV drug use

Question 8

What is the pathophysiology of a PE, why does it cause these symptoms?

Answer 8

• Platelet factor release: serotonin and thromboxane A2 cause vasoconstriction
• Decreased alveolar perfusion: lung is underperfused and this leads to diminished gas exchange
• Decreased surfactant: this leads to ventilation/perfusion mismatch, hypoxia and dyspnoea
• Hypotension caused by decreased cardiac output (Right Heart failure) and vasomotor reflex producing a decrease in systemic arterial resistance

Question 9

How do you investigate a PE?

Answer 9

• D-Dimer level
• Thrombophilia screen
• ABG
• CXR - usually normal
• CTPA (pulmonary angiogram)
• V/Q scanning (isotope scanning) - look for mismatch
• Echocardiogram - rv dysfunction in large PE, tachycardia