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Pulm by Minnie > SM 169a - Pulmonary Embolism > Flashcards

SM 169a - Pulmonary Embolism Flashcards

1
Q

What is the recommended prevention strategy for PE?

A

Thromboprophylaxis in patients with ≥ 1 risk factor

If anticoagulation is contraindicated, use intermittent calf compression

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2
Q

What is a D-dimer?

A

A D-dimer is a product of fibrin degradation

Absence of D-dimers can help to rule out PE, but high levels of D-dimer (>500 mL) is not specific for PE

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3
Q

Wahat is the recommended long-term therapy for PE?

A

One of the following for 3 months if provoked, and at least 3 months if unprovoked or associated with malignancy

  • Vitamin K antagonists
    • Warfarin
  • LMWH
    • Preferred to treat cancer-associated VTE
  • Novel oral anticoagulants
    • Dabigatran (Direct thrombin inhibitor)
    • Rivaroxaban, apixapban, endoxaban (Xa inhibitors)
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4
Q

Cardiovascular collapse in a patient with pulmonary embolism occurs via 2 major pathways.

What are they?

A
  • RV dilation and dsysfunction
    • Leads to decreased RV cardiac output and a septal shift toward the left ventricle
    • This decreases LV preload and cardiac output, leading to hypotension
    • -> Decreased coronary perfusion, which contributes to…
  • RV ischemia and infarction
    • Caused by increased RV wall tension, which increases RV O2 demand and decreases RV O2 supply
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5
Q

Most PEs come from a ____________ extremity

A

Most PEs come from a proximal lower extremity

Ex: popliteal or femoral veins

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6
Q

Outline the diagnostic approach for pulmonary embolism

A
  • Assess the patient’s risk of VTE using a validated risk score
    • Wells ≤ 4 => PE unlikely
      • Run a D-dimer
        • D-dimer ≤ 500 + Wells ≤ 4 => PE excluded
        • D-dimer >500 => PE cannot be excluded
          • CTPA
    • Wells >4 => PE likely
      • CTPA (skip D-dimer)
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7
Q

90 % of PEs are ther esult of an

A

90 % of PEs are ther esult of an embolized DVT

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8
Q

A 75 year old female presents to urgent care with dyspnea. She has a history of a provoked right femoral DVT 10 years ago following a cholecystectomy. She was treated with 3 months of warfarin. Her heart rate is 110 BPM and she is tachypnic, but her blood pressure is normal.

What is the most appropriate next step?

A

Administer unfractionated heparin or LMWH, then perform a CTPA

Her risk profile is very high, so you would skip the D-dimer step. In the meantime, you would want to start anticoagulation given her high risk of PE.

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9
Q

If your mechanically ventilated patient suddenly becomes hypercapnic, what should you be worred about?

A

Pulmonary Embolism

They cannot increase respiration to compensate for the increased dead space, leading to hypercapnia

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10
Q

List some of the physical exam findings that are associated with pulmonary embolism

A

Largely nonspecific

  • Tachypnea
  • Tachycardia
  • Crackles on lung exam
  • Decreased breath sounds
  • Increased P2 component of S2 heart sound
  • Mild hypoxia
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11
Q

What two general factors contribute to the impact of a PE on a patient’s hemodynamic status?

A

Degree of obstruction

+

Baseline health (CV comorbidities?)

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12
Q

If a patient with a PE has contraindications to anticoagulation, what is the recommended acute therapy?

A

IVC filter

If it is a massive PE, also administer systemic fibrinolytic therapy

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13
Q

What is the role of duplex ultrasonography in the diagnosis of PE?

A

Duplex ultrasonography (aka lower extremity compression ultrasound) is great for the diagnosis of DVT

However, a negative lower extremity compression ultrasound does not exclude PE - the clot may have already emoblized

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14
Q

What are the advantages of CTPA?

What are the disadvantages?

A

CTPA = CT pulmonary angiography: the go-to for PE diagnosis

  • Advantages
    • Fast
    • Widely available
    • High diagnostic accuracy esp. for large clots
    • Detailed image helps to make alternative diagnoses
  • Disadvantages
    • Ionizing ratiation and contrast exposure
    • Less accurate for sub-segmental (distal) pulmonary arteries
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15
Q

Are you more likley to see hypocapnia or hypercapnia in a patient with a PE?

A

If a patient is not mechanically ventilated, you are more likely to see hypocapnia

  • PE creates dead space
  • The patient hyperventilates to compensate
  • Hyperventilation -> Hypocapnia

If the patient is mechanically ventilated, they are likely to be hypercapnic; they cannot compensate for the increased dead space

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16
Q

What is the goal of PE therapeutics?

A

Lower the risk of further embolization/clot formation

Allow time for intrinsic fibrinolysis to clear

17
Q

What is Virchow’s triad?

A

Virchow’s triad = risk factors for PE

  • Venous stasis
    • Immobility
    • Age >60
  • Vascular injury
    • Surgery
    • Trauma
    • Post-partum
    • Indwelling vascular access
    • History of VTE
  • Changes in coagulation
    • Hereditary thrombophilias
      • Vactor V Leiden deficiency
      • Prothrombin G2021A
      • Hyperhomocysteinemia
    • Estrogen Therapy
    • Malignancy
18
Q

What is the recommended acute therapy for PE?

A

Acute therapy = first 5 days

  • Heparin
    • Unfractionated or LMWH
    • Start while awaiting test results if pre-test probability of PE is high.
    • Use IVC filter if anticoagulation is contraindicated
  • Fibrinolytics only for patients who have a massive PE
    ​(PE + Hemodynamic shock)
19
Q

Who should recieve systemic fibrinolytic therapy acutely for PE?

A

Patients with a massive PE (PE + hemodnamic shock)

20
Q

% of PEs are ther esult of an embolized DVT

A

90 % of PEs are ther esult of an embolized DVT

21
Q

What is the preferred long-term therapy for VTE associated with malignancy?

A

LMWH

22
Q

What is the difference between a massive PE and a submassive PE?

A
  • Submassive PE = No hemodynamic collapse
    • Associated with RV dysfunction and/or biomarkers of MI injury
  • Massiv PE = Hemodynamic collapse
    • The patient is in shock (SBP <90 mmHg)

The size of the clot is irrelevant!

23
Q

What are the 3 “buckest” that most people with a PE fall into?

A
  1. Pleuritic chest pain +/- hemoptopysis (44%)
  2. Isolated dyspnea (36%)
  3. Circulatory collapse (8%)

Note: Going off of these buckets only misses ~12% of people with PE

24
Q

Why are upper extremity DVTs becoming more common?

A

Venous catheters and venous ports

10% of PEs come from an upper extremity

25
Q

What is the role of ventilation-perfusion scanning (V̇/Q̇ scan) in the diagnosis of PE?

A

A V̇/Q̇ scan is helpful in the diagnosis of PE if it is very normal or very abnormal

  • If it is very abnormal, it is 90% specific for patients with suspected PE
  • If it is very normal, you can safely rule out PE

BUT: 80% of scans are not definitively normal or abnormal, and V̇/Q̇ scan results are even less accurate in patients with COPD or parenchymal disease. Therefore, CTPA is preferred over V̇/Q̇ scan

26
Q

What is the most frequent diagnostic test performed for suspected PE?

Why?

A

Helical computed tomography pulmonary angiography (CTPA or PE-CT)

It is fast, widely available, and has a high diagnostic accuracy, especially for large clots.

It also provides a detailed image that would help to establish alternative diagnoses

27
Q

What is the role of the Pulmonary Embolism Rule Out Criteria (PERC) in diagnosing PE?

A

If none of the PERC criteria are met, the patient has a VERY low risk of PE. You can rule out PE without any diagnostic testing

  • PERC Criteria
    ​(do not need to memorize, just here for reference)
    • Age >50
    • HR ≥ 100
    • Pulse oximitry <95%
    • Unilateral leg swelling
    • Hemoptysis
    • Recent surgery/trauma
    • Prior PE or DVT
    • Exogenous estrogen use
28
Q

What is the role of chest x-ray in the diagnosis of PE?

A

Chest x-rays are good for screening, but they cannot confirm PE

  • They are good at identifying alternative explanations for the patient’s symptoms
  • Most patients with PE do have an abnormal chest x-ray with nonspecific findings
    • Small pleural effusion
    • Basilar atelectasis

Note: if a patient presents with signs/symptoms of PE but has a normal chest x-ray, this should increase you suspicion of PE

29
Q

A patient presents to the ER with pleruitic chest pain. Lung exam reveals decreased breath sounds and tachypnea.

You suspect pulmonary embolism, and calculate a Wells score of 4.

What is your next step?

A

Perform a D-dimer

Wells score ≤ 4 => PE unlikely. Do a D-dimer to confirm

If D-dimer ≤ 500 ng/mL, you can safely rule out PE.
No further testing is needed

If D-dimer > 500 ng/mL, further testing is needed
Order a CTPA, V/Q scan, or angiography

30
Q

What are the advantages of LMWH over unfractionated heparin?

A
  • LMWH has a longer half life, and therefore a higher bioavailability
  • Only patients at the extremes of weight or with renal insufficinecy need to have anti-Xa levels monitored
31
Q

What features of a patients’ clinical history would make you suspect a hereditary thrombophilia?

How would you manage this patient?

A

Unprovoked VET at a young age

Recurrent VTE without other risk factors

Thrombosis at an unusual vascular site

32
Q

What is the difference between provoked and unprovoked PE?

How does this distinction inform the patient’s care?

A
  • Provoked PE
    • There is a clear, reversible, identifiable cause of the PE (ex: the patient was on a 17 hour flight)
    • You only need to administer anticoagulation therapy for 3 months following therapy
  • Unprovoked PE
    • There is no clear cause of PE, or the patient also has cancer
    • You need to administer anticoagulation therapy for at least 3 months, but problably longer

Long term anticoagulation: VKA antagonist (warfarin), LMWH, or novel oral anticoagulant (Dabigatran, Rivaroxaban, apixaban, endoxaban)

33
Q

What is the main cause of hypoxemia in patient with a pulmonary embolism?

A

V̇/Q̇ mismatch

  • If there is atelectasis, pulmonary infacrtion, or intracardiac shunting, a true shunt may be contributing to hypoxemia
  • If it is a massive PE, decreased mixed oxyhemoglobin saturation may be contributing to hypoxemia
34
Q

What are the advantages of unfractionated heparin over LMWH?

A

Unfractionated heparin is readily reversible

35
Q

What is the role of the D-dimer test in the diagnosis of PE?

A

The D-dimer test is sensitive but not specifc for PE

  • A low D-dimer can help to rule out PE
  • However, a high D-dimer (>500 ng/mL) cannot diagnose PE definitively
36
Q

What are the advantages of duplex ultrasonography?

What are the disadvantages?

A
  • Advantages
    • Cheap
    • Repeatable
    • Noninvasive
    • No radiation or contrast exposure
    • Does not require extensive specialized training
    • Great for diagnosing DVE
  • Disadvantages
    • A negative ultrasound does not rule out PE
37
Q

Death from pulmonary embolism is usually due to __________.

A

Death from pulmonary embolism is usually due to cardiovascular collapse.

38
Q

A patient presents to the ER with pleruitic chest pain. Lung exam reveals decreased breath sounds and tachypnea.

You suspect pulmonary embolism, and calculate a Wells score of 5.

What is your next step?

A

Perform a CTPA

Wells score >4 => PE likely. Even a negative D-dimer would not rule out PE, so go straight to CTPA

39
Q

What is the “diagnostic gold standard” for PE?

Why isn’t it used widely for PE diagnosis?

A

Contrast venography and pulmonary angiography

It is invasive, exposes the patient to contrast, not highly accurate for small clots, and requires a high level of expertise to perform

CTPA (PE-CT) is used most commonly

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