Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE)

What is Thrombus?

• A blood clot that forms inside blood vessels (vein or artery)

• Obstructs blood flow

• Platelets (thrombocytes) and fibrin form a blood clot to prevent blood loss after injury

• Clots can also form without injury with certain risk factors

• A clot that breaks free and travels around the body is an embolus

What three factors together greatly increase the risk of a thrombus occurring?

Virchow’s Triad

• Hypercoagulation

• Stasis

• Endothelial Damage

Describe the stasis (causes) of thrombus occurring?

Varicose Veins / Haemorrhoids:

• Back flow of blood

• Incompetent valves result in stagnant blood

Compression:

• Pregnancy weight increased compression of the iliac vein

Lack of muscular contraction:

• Not ambulating after LSCS

• Inactivity

• Airplane travel

• Long car rides

• Lack of muscle tone

What is hypercoagulation?

A state where a condition causes the blood to clot more easily than normal

• There may be an increase in procoagulation enzymes - increases clot formation

• There may be a decrease in anticoagulent enzymes - fewer enzymes to break down clots

What conditions contribute to hypercoagulation?

Can be acquired or inherited

• Acquired - pregnancy, birth control (contains oestrogen), cancers (lung, pancreatic), obesity, nephrotic syndrome

• Inherited - genetics, Factor 5 Leiden, Protein C or S deficiency, Anti - prothrombin 3 deficiency

• Autoimmune - Lupus, antiphospholipid syndrome (maybe also genetic)

Oestrogen is a procoagulant

True or False? Why?

True.

• Produced by the Ovaries

• Later by the placenta

• Helps the uterus grow

• Maintain the uterine lining

• Triggers baby growth

• Hormone regulation

• Oral contraceptive (oestrogen)

• The exact molecular mechanism is not known

Describe hypercoagulation in obesity

• All points of the Triad are present (Stasis, Hypercoagulation, Endothelial Injury)

• Obesity increases the release of Interleukin 6 and CRP – both are produced in response to infections, inflammation, and tissue injury

Describe inherited/genetic/autoimmune hypercoagulation

• Factors V Leiden (genetic) is an increase in pro-coagulation enzyme

• Prothrombin gene mutation

• Protein C & S deficiency and Antithrombin Antiphospholipid Syndrome (autoimmune) - seen in Lupus, SLE (systemic lupus); antibodies attack anticoagulant enzymes, protein C & S resulting in a decrease in anti-coagulants (these enzymes normally help break down clots) increasing the risk of clots

Describe factors of endothelial injury or damage

• Vascular endothelial injury

• Surgery

• Smoking - endotoxic injury

• Obesity - cytokine release, CRP increase

• Catheters - vascular

What are the clinical features of DVT?

• Lower extremity: usually calf

• Swelling

• Pain

• Redness

• Low-grade fever

• Difficulty weight bearing

• Diagnosed by ultrasound & D-dimers (D-dimers not used in pregnancy)

• Positive Homan sign ( is not relevant to pregnant or postpartum women)

What is a Pulmonary Embolism?

A blood clot in the pulmonary arterial circulation

Describe the characteristics of a clot in the pulmonary circulation

• Part or all the clot releases from its initial site and enters the bloodstream

• The clot enters the pulmonary circulation, enters a pulmonary artery or arteriole (dependent on the size of the clot

• This then affects the gaseous exchange process

What are the signs & symptoms of a Pulmonary Embolism (PE)?

• Shortness of breath, cough (haemoptysis), pleuritic pain

• Chest pain, tachycardia, hypotension, right sided cardiac failure

• Syncope, hypoxaemia, cyanosis

• Fever, dizziness, diaphoresis

• Sense of impending doom

• Signs of cause (e.g. leg swelling if DVT)

What are the increased risks of DVT & PE?

• Previous VTE

• Age >35

• Obesity (BMI >30kgm)

• Active medical illness

• Smoking

• Family history of VTE

• Immobility

• Varicose veins

What are pregnancy - specific risk factors of DVT & PE?

• Multiparity (>2)

• Multiple Pregnancy

• Assisted reproduction technology

• Hyperemesis

• Preeclampsia

• Planned c/s

• Emergency c/s

• Placental abruption

• Placental infection

• PPH

In what ways can DVT & PE be prevented?

• Avoid immobility

• Avoid legs in stirrups for long periods

• Thromboprophylaxis

• TED stockings

• SCDs devices

How is PE diagnosed?

• ECG

• ECG doppler

• Clotting profile

• CT scan

• MRI

• Chest X - Ray

• Blood gasses

• Pulmonary angiogram