Diagnosis and Treatment of Pulmonary Embolism

Question 1

Why do emboli end up in the lungs?

Answer 1

All blood goes through the lungs
Lungs act as a protective filter - better able to deal with emboli than areas in systemic circulation such as the brain.

Question 2

Why are the lungs an adapted organ to be the site of emboli/thrombi?

Answer 2

Immune organ - increased B and T cell response
Anti-inflammatory in highly oxidative environment
Have a high capacity to cope with some damage to lungs - shown by good survival after pneuomonectomy.

Question 3

What are the different types of embolism?

Answer 3

Mycotic (infective)
Fat
Air
Thrombotic

Question 4

Where to thrombotic pulomonary embolisms normally arise from?

Answer 4

Mostly from deep veins of the legs (iliac, femoral and popliteal)
Also be from IV lines or upper limb

Question 5

What is Paget Schroetter related to upper limb thrombosis?

Answer 5

When the upper limb has an increased risk of a DVT in the axillary or subclavian veins due to extrinisic compression or repetitive injury
Often from the subclavian vein being pressed against the junction of the first rib and the clavicle
May be termed effort thrombosis.

Question 6

What is a mycotic embolus?

Answer 6

A transfer of infective pathogens to lungs from a distant source

Question 7

What are the common causes of a mycotic embolus?

Answer 7

Intravenous drug use - iatrogenic drug infusion, blood transfusions or illicit drug use.
Infective endocarditis.

Question 8

What signs can indicate a mycotic emboli?

Answer 8

Oslers nodes, Janeway lesions, roth spots and splinter haemorrhages Indicates systemic emboli often from infective endocarditis.
Oslers nodes - digits, pink with pale centre, painful
Janeway lesions - non-painful, patches on palm of hands
Splinter haemorrhages - red/purple lines under nail bed following direction of nail growth.
Roth spots - small haemorrhages on eyes

Question 9

How might infective endocarditis by indentified in the heart?

Answer 9

Ultrasound - greyscale (growth around the valve)

Question 10

What imaging technique is commonly used to visualise a potential embolus/thrombus in the lungs?

Answer 10

Chest CT
Chest angiogram.

Question 11

What causes a fat embolus?

Answer 11

Normally a fracture in a long bone - where large amounts of fat-containing bone marrow can be released.
Causes multifocal inflammation in the lungs.

Question 12

What causes an air embolus?

Answer 12

Occurs from incorrect canulation that then allows gas into the veins
In most scenarios the lungs act as a filter and are able to deal with the air embolus
However, in certain scenarios such as (Osler-Weber-Rendu) can be fatal and care should be taken not to inject certain patients unnecessarily

Question 13

What is Osler-Weber-Rendu syndrome?
How does this link to pulmonary embolus?

Answer 13

Is a genetic autosomal dominant condition
Causes the formation of AV anatamosis in the skin, mucosa, GIT and lungs etc.
These anastomosis already cause respiratory problems for the patient - hypoxemia, haemorrhage
Also allow passage of an emboli from pulmonary to systemic circulation (without return to the heart) this is known as a paradoxical emboli
May predispose the patient for a cerebral abscess or stroke.

Question 14

How do patients with Osler-Weber-renu syndrome often present?

Answer 14

Most to least common symptoms
Nose bleeds
Skin, lips and mouth telangescesica
Pulomonary, hepatic AVMs
GIT bleeds
Cerebral AVMs
Spinal AVMs.

Question 15

What is the consequence of a large air emboli in the heart?

Answer 15

Heart chamber does not fill with blood as is airlocked
Heart contracts around air
Causes sudden cardiocirculatory collapse and sudden death.

Question 16

What is cardiocirculatory collapse?

Answer 16

Severe hypotension resulting in cerebral hypoperfusion and loss of consciousness
Decreased blood flow to organs can be fatal.
Cause of sudden death.

Question 17

What is the dual circulation to the lungs?
How is this beneficial?

Answer 17

The pulomonary arteries supply deoxygenated blood to the lungs, which is them oxygenated and returned to the heart via the pulmonary veins

The bronchial arteries provide high pressure oxygenated blood to the lungs to supply the parenchyma, then drain back via the bronchial veins into systemic circulation.

Question 18

Why are the lungs less sensitive to damage from emboli than other areas?

Answer 18

Dual circulation - pulmonary obstruction, bronchial arteries can oxygenate the tissue.
Abundant collateral circulation to different areas of the lungs.
Alveoli are full of air so simple diffusion will supply the cells to a degree.
Tissues are less sensitive to anoxia
Because of the extensive collateral circulation and the efficiency of gas transfer there is minimal impact on O2 saturation assuming the emboli are small and not continuously arriving.

Question 19

How does the rate of thrombus/air emboli absorption vary from the lungs to other tissue?

Answer 19

The lungs absorbed all emboli faster than other tissue
However, thrombotic emboli always take longer to absorb than air in all tissue
The more sensitive to anoxia a tissue is the longer it will likely take to absorb an emboli.

Question 20

What does Virchows triad state will increase the risk of thrombus formation?

Answer 20

Venous statis - immobile patients, long flight, after surgery etc
Endothelial disruption/surgery - around cannulas, central lines or from hypertension
Hypercoagulability - obesity, smoking, cancer, antiphospholipid syndrome.

Question 21

How common is it for a DVT to form a PE?

Answer 21

50% untreated DVT will form a PE

Question 22

What are some statistics showing why the number of pulmonary embolisms is so high?

Answer 22

80% of pelvic surgery patients develop DVT post surgery
- Common cause of adult sudden death, in patient death and all deaths.
The risk of DVT increases with age

Question 23

What are the pathological consequences of a PE?

Answer 23

The lung tissue is ventilated but not perfused, this area of lung may infarct (chest pain) but often does not due to the collateral blood supply.
Results in intra-pulmonary dead space and impaired gas exchange (resulting in shortness of breath)
Reduction in cross-sectional area of the pulmonary arterial bed
Elevation of pulmonary arterial pressure
Reduction in cardiac output as left heart filling decreases, high RA pressure can reopen the patent foramen ovale.
Potential circulatory collapse and cardiac arrest due to RVD
Alveolar collapse occurs worsening hypoxemia.

Question 24

What are the outcomes of a pulmonary embolism?

Answer 24

Untreated PE - 10% die within one hour and 30% die within 1 month
67% of deaths are not diagnosed pre-mortem
34% show rapid detrioration prior to death making them hard to treat fast enough
If PE is treated it reduces your risk of mortality by 5%
Recurrence depends on risk factors - 2 to 4% of people have reoccurences of which 5 to 7% are fatal.

Question 25

What is the use of D-dimer as a test for pulmonary embolism?

Answer 25

D-dimer indicates fibrinolysis has occurred - hence thrombus formation must have also occurred Therefore will be elevated in a PE has occured 95% sensitivity, 50% specificity. Low specificity means only has negative predictive value aka - if low value can rule out PE as a differential diagnosis.

Question 26

What can cause a D-dimer score to increase?

Answer 26

PE Inflammation, infection, cancer Also increases naturally with age.

Question 27

What is the purpose of Wells Scoring for PE?

Answer 27

NICE recommends the use of the original score Wells score for PE A score over 4 indicates PE is likely, a score below 4 indicates a PE is unlikely. A score of three is given for clinical signs/symptoms of DVT, alternative diagnosis is less likely. A score of 1.5 is given for HR above 100, immobilisation, previous DVT/PE A score of one is given for haemoptysis or active cancer.

Question 28

What is the use of a ultrasound in the diagnosis of a PE/DVT?

Answer 28

Greyscale ultrasound - vein should be compressible if not compressible indicates a thrombus Can be done from the CFV to the diaphragm From the PV to the ankle Excellent specificity and good sensitivity

Question 29

What is the use of doppler ultrasound in the diagnosis of a PET/DVT?

Answer 29

Doppler showing an absence of venous flow indicates a thrombus.

Question 30

What is V/Q matching?

Answer 30

Stands for ventilation (air) perfusion (blood) mismatch Pulmonary vessels normally constrict and dilate to ensure plentiful blood flow to alveoli that are well ventilated and vice versa

Question 31

What is a pulmonary dead space?

Answer 31

An area of the lung with ventilation but inadequate perfusion, pulmonary arteriolar vasoconstriction Oxygen can not enter the bloodstream This could be anatomic in cause - e.g no blood flow Or physiological in cause - not enough blood flow.

Question 32

What is meant by a pulmonary shunt?

Answer 32

Shunt occurs when there's adequate blood supply/perfusion but low inadequate ventilation.

Question 33

What is a V/Q scan?

Answer 33

A ventilation scan and a perfusion scan Can be compared to identify a VQ mismatch. Used with SPECT is more sensitive than a planar image Only requires a low dose of contrast. Is useful in pregnancy and post-partum However, is highly dependent on reporter confidence and expertise Up to 66% have a non-diagnostic result

Question 34

What is the usefulness of an echocardiography in a pulmonary embolism formation?

Answer 34

Only images the heart not the lungs Useful for assessing hemodynamic effects of current embolic burden. May suggest mortality by identifying RV strain or co-existent heart disease Has a poor sensitivity and poor specificity for PE as only indicates changes in heart not why changes have occured.

Question 35

What is a CTPA?

Answer 35

A CT pulmonary angiogram Contrast media is used to opaque the pulmonary arteries and check for occlusions 83% sensitivity and 96% specific to PE Has a high negative predicietive power and low and intermediate risks There are 3 generations of CT scanners meaning high spatial and temporal resolution, greater confidence/experience from reporters

Question 36

What are the drawbacks from the use of a CTPA?

Answer 36

Test is highly available may be over ordered, parituclary in specialities with little experience with PE, leading to lower hit rate and need to traige CTPA Radiation dose can increase young patients relative lifetime risk of cancer by 5% - particularly important in peri-partum mums. Large amount of artefacts. Difficult to diagnose subsegmental PE Uncertainty around safety of giving a person on warfarin (blood thinners) a CT.

Question 37

What is a PE overcall and what are the consequences of this?

Answer 37

An overcall is to diagnose a condition that does not actually exist 6% interderterminate rate in PECT diagnosis This has consequences because of the mortality rate associated with treatment Warfarin - 3% morbidity per year and 1% mortality per year In STSFT 1 mortality per 18 months from overcalls.

Question 38

What are some of the potential treatments for a PET?

Answer 38

LMWH initially followed by heparin (3% mb, 1% mortality) NOAC - similar efficacy and reduced M&M, however is overdose does occur are more difficult to reverse Bleeding risk in patients - use a LAA occlusion device or an IVC filters .

Question 39

How long should treatment last for patients with a thromboembolism?

Answer 39

If occured due to a strong, transient risk factor considered provoked e.g after srugery so is unlikely to occur again - offer 3 months of treatment If occurred due to ongoing strong risk factors such as cancer or unprovoked events there is an increased risk of reoccurrence and should be considered for extended treatment

Question 40

What are some major risk factors for a PE?

Answer 40

DVT Previous DVT or PE Active cancer Recent surgery - particularly pelvic surgery Lower limb trauma Significant immobility, for example due to hospitalisation Pregnancy, particularly 6 weeks post partum

Question 41

What are some minor risk factors for a Pulmonary embolism?

Answer 41

Use of the combined oral contraceptives or hormone replacement therapy Known thromophilias Long distance travel Obesity Increasing Age.

Question 42

What are the risks and management associated with a subsegmental PE?

Answer 42

Requires more sensitive CT scanners or can be missed Debateable if overdiagnosis - normal lung function to catch these emboli No proper randomised control trials to show if treatment is necessary Majority are treated with antti-coagulation Subsegmental PE with no proximal DVT is thought to have low clinical risk, patients are high risk once on anticoagulant therapy

Question 43

How does the British Thoracic Society calculate the pulmonary embolism severity index?

Answer 43

Factor - score Age - age in years Male - + 10 Cancer - + 30 Heart failure +10 Chronic lung disease +10 Pulse above 110 +20 Systolic BP above 100 +30 RR above 30 +20 Temperature below 36 +20 Altereted mental status +60 Arterial blood oxygen saturation +20. Considers patient demographics, health status and clinical findings to calculate a score to indicate their risk of mortality from a DVT within the next 30 days

Question 44

How does the Pulmonary Embolism Severity Index score influence the clinical management of a patient?

Answer 44

Score correlates to risk lower score (below 85) are low risk and can be treated at home Intermediate cases may need discussion but could be treated as an in or outpatient In patient treatment should be given to all patients scoring 106 or above because these are high or very high risk of mortality in the next 30 days.

Question 45

What tends to be the outpatient treatment for patients with a pulmonary embolism?

Answer 45

Administered LMWH CTPA as outpatient within 24hours.

Question 46

What can facotrs means a patient with a PE is not suitable to be an outpatient?

Answer 46

Considerd PESI score Haemodynamically unstable, active bleeding, severe liver impairement, pregnancny, history of herpain induced thrombocytopenia among many more

Question 47

What are the risks and potential treatment strategies from a massive pulmonary PE?

Answer 47

High risk of cariogenic shock and cardiovascular compromises and cardiovascular collapse. Evidence suggests that a fibrinolytic (streptokinase) should be used alongside heparin rather than just heparin alone.

Question 48

What are the risks and management associated with a submassive (intermediate) PE?

Answer 48

Fibrinolytic/anti-coagulants decrease risk of PE but increase risk of major hemorrhage and stroke Mortality is hight and tends to be no benefit from thrombolysis, catheter directed thrombolysis or low dose may be potential options to reduce risks of treatment Submassive show RV dysfunction Also produce cardiac biomarkers such as BNP, NpBNP and Troponin assay.

Question 49

What is the clinical approach to deciding to treat a patient with an acute PE? (high risk)

Answer 49

If patient shows evidence of Acute PE including shock hypotension consider if high, intermediate or low risk If high risk give systemic thrombolysis unless contraindicated then consider surgical embolectomy or catheter direct thrombolysis if contraindicated

Question 50

What is the clinical apprahc guidance for a patient with a low or intermediate risk PE?

Answer 50

Consider PESI is above 2 then test for RV dysfunction and elevated biomarkers If present treat as high risk patient If not present that treat with anti-coagulation If PESI below 2 then patient is low risk and should be treated with anti-coagulation.