20/21 - Pulmonary Vascular Disease & Cases Flashcards
What is an embolus?
A detached intravascular solid, liquid, or gaseous mass carried by the blood to a site distant from its point of origin.
Inevitably, emboli lodge in small blood vessels causing occlusion.
What are the different types of emboli?
- Thrombus
- Gas/air
- Fat
- Tumor
- Amniotic fluid
- Bone marrow
Where do pulmonary emboli originate?
Vast majority originate in the legs (deep veins); some in the pelvis or abdomen.
In-site pulmonary thrombosis are rare but can happen with pre-existing pulmonary HTN.
Where do thrombi in the deep veins of the legs go?
To the right side of the heart through the superior or inferior vena cava to the right atrium and right ventricle.
It then lodges in one of the branches of the pulmonary artery and obstructs blood flow which causes an infarction in the lung.
What is Virchow’s Triad?
The three factors that contribute to thrombosis:
Endothelial injury: ulcerated plaque, trauma, inflamm vascular injury (vasculitis), indwelling deviecs.
Hypercoagulability: Aneurysms, acute MI, atrial fibrillation, decreased mobility, surgery.
Stasis: Favtor V leiden, prothrombin gene mutation,
What does the clinical significance of PE depend on?
- Extent to which the pulmonary artery blood flow is obstructed.
- Size of occluded vessel
- Number of emboli
- Pre-existing cardiopulmonary status
- Release of vasoactive substances such as thromboxane A2 from activated platelets.
What are some ways that there is pulmonary compromise with a PE?
- Ventilation of non-perfused area
- Increased dead space
- Increased work of breathing
- Worsening ventilation-perfusion matching
- Hypoxemia, hypercapnia, resp. failure
What are some ways that there is cardiac compromise with a PE?
- Increased resistance to flow of blood from RV through to LA.
- Acute RV failure
- Remember that RV and LV are connected in series
- RV falis; LV gets progressively under-filled
- Shock/death
What are clinical sympatoms associated with PE? How is it diagnosed?
Chest pain, dyspnea, hypotension, low grade fever (from plately activation and cytokine release)., cough, hemoptysis, sudden cardiac death.
Usually diagnosed with CT scan of the chest.
How are PEs treated?
Usually treated with anticoagulation such as heparin and rarely throbolysis.
This is because heparin prevents more clots from forming and the current clot from getting bigger. It also allows time for the body to break fown the embolus itself.
How can pulmonary infarction occur?
Smaller emboli travel to the peripheral vessels and may cause hemorrhage.
Very rarely, the emboli cause infarction. Bronchial circulation comes from the aorta, and sustains the pulmonary parenchyma.
- This is not very common due to dual blood supply (bronchial and pulmonary)
Where are pulmonary infarcts more common and why?
Most affect the lower lobes because that’s where there’s more perfusion.
- typically wedge shaped extending out from the ischemic focus to the periphery
- usually hemorrhagic infarct
- Eventually heal and leave a small scar
What is the difficulty in diagnosing a PE?
The signs and symptoms are non-specific and therefore you need to have a high clinical suspicion of PE in order to rule out other potential causes of the symptoms.
What do pulmonary emboli cause mechanistically?
- Hypoxia, by worsening ventilation/perfusion mismatch
- Release of local inflamm mediators which cause bronchocontriction
- Strain on RV (has to pump across a clogged up circulation)
- Decreased venous return to left ventricle due to above
- Potential cardiac collapse and sudden death
Why might you not want to diagnose PE with a CT?
CT chest is may be contraindicated due to renal failure (note that diagnosing PE requires IV contrast)
**this was from the case in class and it may not always be the case**
What does this look like in terms of lung pathology?
Small cell lung cancer
Where is adenocarcinoma typically found in the lung? Who gets this type of cancer?
More peripherally (contrast from small cell and squamous that are more centrall)
Most common lung cancer in non smokers (smoking is still a risk factor tho!)
Increasing incidence in women
Where in the lung is squamous cell lung cancer found? What is it associated with? What does it look like on histology?
Often found centrally. Strong association with smoking and hypercalcemia.
Can see keratin pearls on histology.
How common is pulmonary artery hypertension (formerly called primary pulmonary HTN)?
RARE! This is why the diagnosis is often delayed, because you’re not thinking about it much because it’s RARE.
