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Y2 MECHANISMS OF DISEASE > Pulmonary Embolism > Flashcards

Pulmonary Embolism Flashcards

1
Q

What is the definition of pulmonary embolism?

A

Blockage of an artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream

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2
Q

What are the 5 types of pulmonary embolism?

A
  1. thrombus (DVT)
  2. fat embolus
  3. air embolus
  4. amniotic fluid embolus
  5. foreign material
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3
Q

what are the non-specific symptoms associated with pulmonary embolus?

A
  1. dyspnoea
  2. tachypnoea
  3. pleuritic chest pain
  4. cough
  5. haemoptysis
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4
Q

What are the more severe symptoms associated with pulmonary embolus?

A
  1. haemodynamic instability
  2. collapse/syncope
  3. sudden death
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5
Q

What is an issue when performing an examination for a suspected pulmonary embolism?

A

The findings are very non specific

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6
Q

What are typical findings associated with pulmonary embolism?

A
  1. tachycardia
  2. tachypnoea
  3. pleural rub/effusion
  4. raised JVP
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7
Q

What is significant about the clinical findings of someone with pulmonary embolus?

A

they are all associated with right heart strain

this is because there is increased work load due to increased resistance in the pulmonary circulation

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8
Q

What is the the ECG pattern associated with pulmonary embolus?

A

S1 Q3 T3

S waves in lead 1

Q waves in lead 3

Inverted T waves in lead 3

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9
Q

How can the risk factors for VTE be classified?

A

By Virchow’s triad

This includes:

  1. stasis
  2. vessel wall injury
  3. hypercoagulability
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10
Q

What is meant by unprovoked and provoked VTEs?

A

Provoked has a clear cause - e.g. following trauma or surgery

Unprovoked has no known cause

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11
Q

Why is it important to know whether a VTE is provoked or unprovoked?

A

It affects the risk of recurrence and influences what treatment should be given to the patient

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12
Q

If a patient presents with signs or symptoms of a pulmonary embolism, what should be done?

A

carry out an assessment of their general medical history

a physical examination

a chest X-ray to exclude other causes

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13
Q

What should be done if a pulmonary embolism is suspected after initial assessment?

A

the two-level PE Wells score is used to estimate the clinical probability PE

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14
Q

What are the clinical features in the Wells score that are awarded 3 points?

A
  1. clinical signs and symptoms of DVT

2. an alternative diagnosis is less likely than PE

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15
Q

What are the clinical features in the Wells score that are awarded 1.5 points?

A
  1. heart rate > 100 beats per min
  2. immobilisation for more than 3 days or surgery in the previous 4 weeks
  3. previous DVT/PE
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16
Q

What are the clinical features in the Wells score that are awarded 1 point?

A
  1. haemoptysis

2. malignancy (on treatment, treated in the last 6 months, or palliative)

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17
Q

What does a Wells score show?

A

PE is likely if score is MORE than 4 points

PE is unlikely if score is 4 points or less

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18
Q

What test is offered if PE is unlikely and Wells score is 4 or less?

A

D-dimer test

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19
Q

What happens if the D-dimer test is negative?

A

assume there is no PE

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20
Q

What happens if the D-dimer test is positive?

A

Then it is treated that PE is likely and CT pulmonary angiogram is conducted

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21
Q

What test is performed if PE is likely and Wells score is more than 4?

A

CT pulmonary angiogram

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22
Q

What happens based on the results of the CTPA?

A

if it is negative, consider repeat D-dimer

if it is positive, treat as PE

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23
Q

What does a D-dimer test measure?

A

It measures fibrin degradation products that are produced when a clot is broken down

24
Q

How do the clotting cascade and fibrinolysis system work at the same time during clotting?

A

thrombin converts soluble fibrinogen to insoluble fibrin

fibrin is crosslinked by factor 13 to form the scaffolding of the blood clot

at the same time, the fibrinolysis system involves plasmin breaking down the mesh work to form D-dimers

25
Q

What is the normal concentration of D-dimer in the blood?

A

D-dimers are not normally present in the blood at a meaningful concentration

They are only present when the coagulation system has been activated

26
Q

What is the sensitivity of D-dimer test like?

A

93-95% sensitivity

27
Q

When may false negatives occur in the D-dimer test?

A

they are rare

they occur when a sample is delayed or too early

or if the patient is on anticoagulants

28
Q

When may false positives occur in the D-dimer test?

A
  1. liver disease
  2. inflammation
  3. malignancy
  4. trauma
  5. pregnancy
  6. recent surgery
29
Q

What is injected during a CTPA?

How can this identify an embolus?

A

Iodine based contrast is injected

All blood vessels should show up as bright white

Any dark filling detected is an embolus

30
Q

What type of patients is CTPA not suitable for?

A

patients with renal failure, allergy to iodine, pregnancy

31
Q

What is an alternative test that can be used to diagnose pulmonary embolism?

A

VQ scan (ventilation perfusion mismatch scan)

radioactive molecules are inhaled/injected and the difference in the 2 scans are identified

32
Q

What scan is used to diagnose PE in pregnancy?

A

usually a doppler scan on the leg is performed to look for a DVT

33
Q

What determines the acute treatment that a patient with PE receives?

A

The severity of the PE

34
Q

What are the 4 main acute treatments for PE?

A
  1. supportive therapy - IV fluids, inotropes, respiratory support
  2. acute phase anticoagulation and initiate VKA
  3. primary reperfusion
  4. embolectomy
35
Q

What scoring system is used to determine the severity of a pulmonary embolism?

A

PESI - pulmonary embolism severity index

36
Q

What is an embolectomy?

A

the removal of a blood clot/embolism through surgery

37
Q

What is the recommended anticoagulant used in treating PE?

A

unfractionated heparin

38
Q

Why is UFH the main anticoagulant used in PE?

A

It has a short half life

It is reversible

It is easy to monitor

39
Q

How can UFH be reversed?

Why might this happen?

A

reversible with protamine

e.g. if a patient is going to go to theatre

40
Q

What are examples of oral anticoagulants?

Which require heparin before administration?

A

rivaroxaban and apixaban do not need heparin first

dabigatran and edoxaban need an initial supply of heparin to be given first

41
Q

What are the benefits of oral anticoagulants?

A
  1. reduced risk of major bleeding
  2. rapid onset of action
  3. short-acting
  4. do not require monitoring
42
Q

Which patients should UFH always be prescribed?

A

Obese and anorexic patients

patients with renal impairment

43
Q

Which patients with PE should always be given LMWH?

A
  1. active cancer
  2. hepatic impairment
  3. coagulopathy
  4. pregnant patients
44
Q

Why should LMWH be given to pregnant patients?

A

It does not cross the placenta

45
Q

What is significant about Fondaparinux (oral anticoagulant)?

A

it carries a low risk of inducing heparin-induced thrombocytopenia (HIT)

46
Q

what is HIT?

A

heparin induces an immune reaction

antibodies are produced to the body’s own platelets

this reduces the platelet number and leads to a DIC phenotype

47
Q

What are the absolute contraindications for primary reperfusion?

A
  1. haemorrhagic stroke
  2. ischaemic stroke in the preceding 6 months
  3. central nervous system damage or neoplasms
  4. recent major trauma/surgery
  5. gastrointestinal bleeding within the last month
  6. known bleeding risk
48
Q

What are the relative contraindications for primary reperfusion?

A
  1. transient ischaemic attack in preceding 6 months
  2. oral anticoagulation therapy
  3. pregnancy, or within 1 week postnatally
  4. traumatic resuscitation
  5. refractory hypertension
  6. advanced liver disease
  7. infective endocarditis
  8. active peptic ulcer
49
Q

What is catheter directed therapy and when is it used?

A

giving the thrombolytic agent directly at the site of the thrombus

this is commonly used for large DVTs

50
Q

What is the benefit of catheter directed therapy?

A

localising the drug minimises the bleeding risk

it can also be given at a lower dose

51
Q

When is a surgical embolectomy usually performed?

A

if systemic thrombolysis is given and there is no improvement in the patient

52
Q

What is an IVC filter and why is it used?

A

it is placed in the inferior vena cava in patients who have had multiple recurrent PEs

This works by trying to stop the clots reaching the lungs

53
Q

What is the ongoing anticoagulation for patients with a PE provoked by surgery?

A

3 months at least of anticoagulation

this is usually with warfarin or UFH

54
Q

What is the ongoing anticoagulation for patients with a PE provoked by a non-surgical transient risk factor?

A

3 months

55
Q

What is the ongoing anticoagulation for patients with unprovoked PE with low or moderate bleeding risk?

A

extended anticoagulation therapy

56
Q

What usually causes an amniotic fluid embolus?

A

A tear in the placental vein or defects in the gynaecological vessels

This can lead to amniotic fluid entering the maternal circulation

Y2 MECHANISMS OF DISEASE (36 decks)

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