SM 169a - Pulmonary Embolism Flashcards
What is the recommended prevention strategy for PE?
Thromboprophylaxis in patients with ≥ 1 risk factor
If anticoagulation is contraindicated, use intermittent calf compression
What is a D-dimer?
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
Wahat is the recommended long-term therapy for PE?
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)
Cardiovascular collapse in a patient with pulmonary embolism occurs via 2 major pathways.
What are they?
- 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
Most PEs come from a ____________ extremity
Most PEs come from a proximal lower extremity
Ex: popliteal or femoral veins
Outline the diagnostic approach for pulmonary embolism
- 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
- Run a D-dimer
-
Wells >4 => PE likely
- CTPA (skip D-dimer)
-
Wells ≤ 4 => PE unlikely
90 % of PEs are ther esult of an
90 % of PEs are ther esult of an embolized DVT
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?
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.
If your mechanically ventilated patient suddenly becomes hypercapnic, what should you be worred about?
Pulmonary Embolism
They cannot increase respiration to compensate for the increased dead space, leading to hypercapnia
List some of the physical exam findings that are associated with pulmonary embolism
Largely nonspecific
- Tachypnea
- Tachycardia
- Crackles on lung exam
- Decreased breath sounds
- Increased P2 component of S2 heart sound
- Mild hypoxia
What two general factors contribute to the impact of a PE on a patient’s hemodynamic status?
Degree of obstruction
+
Baseline health (CV comorbidities?)
If a patient with a PE has contraindications to anticoagulation, what is the recommended acute therapy?
IVC filter
If it is a massive PE, also administer systemic fibrinolytic therapy
What is the role of duplex ultrasonography in the diagnosis of PE?
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
What are the advantages of CTPA?
What are the disadvantages?
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
Are you more likley to see hypocapnia or hypercapnia in a patient with a PE?
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
What is the goal of PE therapeutics?
Lower the risk of further embolization/clot formation
Allow time for intrinsic fibrinolysis to clear
What is Virchow’s triad?
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
- Hereditary thrombophilias
What is the recommended acute therapy for PE?
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)
Who should recieve systemic fibrinolytic therapy acutely for PE?
Patients with a massive PE (PE + hemodnamic shock)
% of PEs are ther esult of an embolized DVT
90 % of PEs are ther esult of an embolized DVT
What is the preferred long-term therapy for VTE associated with malignancy?
LMWH
What is the difference between a massive PE and a submassive PE?
- 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!
What are the 3 “buckest” that most people with a PE fall into?
- Pleuritic chest pain +/- hemoptopysis (44%)
- Isolated dyspnea (36%)
- Circulatory collapse (8%)
Note: Going off of these buckets only misses ~12% of people with PE
Why are upper extremity DVTs becoming more common?
Venous catheters and venous ports
10% of PEs come from an upper extremity
