What are the (4) steps of thrombus activity?
- Propagation as it enlarges and occludes or embolizes
- Embolization as it is dislodged and transported elsewhere
- Recanalization as original lumen is reformed (smooth muscle cells, fibroblasts, etc.)
- infection if bacterial seeding occurs which may lead to mycotic aneurysm
What does recanalization of a thrombus look like?
- End-stage of thrombus
- Blood clot is replaced by connective tissue w/ many new channels
- Channels can re-establish blood supply and acquire/maintain perfusion
- Multiple lumens form to facilitate this function
C&C venous thrombi versus arterial thrombi
Venous Thrombi
* Gradual onset of pain, swelling, congestion, edema due to obstruction
* Potential embolization of lungs (PE) from (DVT of around knee joint (e.g., femoral, popliteal, iliac veins))
Arterial Thrombi
* Sudden onset of ischemia and obstruction
* May embolize
What is an embolus?
Detached intravascular solid, liquid, or gaseous mass that is carried by blood to a distant site to occlude a vessel leading to tissue dysfunction or infarction
What type of embolism would you see from a patient with a fracture of a long bone?
Fat droplet emboli
What type of fluid can lead to embolism during parturition?
Amniotic fluid
What type of HF will you note from a patient with a PE?
Right sided HF
What is the pathogenesis of PE?
- Virchow’s Triad leads to a DVT
- Ends up within the pulmonary arteries from IVC where it will obstruct pulmonary artery
- Leads to surfactant dysfunction
- Triggers hyperventilation
- Multiple occurring at one time can lead to PHTN & RV failure (cor pulmonale)
Triad: hypercoagulability, hydrostasis, endothelial dysfunction
What vein most commonly leads to PE?
Iliac vein
S/Sx of cholesterol embolization syndrome.
- Acute renal failure (cholesterol crystal embolization of kidneys)
- Skin involvement (purura, necroses, livedo reticularis)
- Blue toe syndrome
- Gastrointestinal involvement
- CNS symptoms (TIA, Stroke)
What type of shock is noted in fat embolism?
Obstructive shock
Due to fat emobli lodged in pulmonary vessels
What is the classic triad of fat embolism?
RAN
* Rash: petechial rash – capillary obstruction
* ARDS (acute respiratory distress)
* Neurological symptoms: confusion, lethargy, seizures
What is Caisson disease?
- Gas emboli in bones leads to multifocal ischemic necrosis
- Heads of long bones
How to Tx decompression sickness?
High-pressure air chamber
Forces gas back into solution
Which gas is most responsible for decompression sickness?
Nitrogen
Explain decompression sickness.
- Rapid formation of gas bubbles within skeletal muscle and joints leads to pain
- Gas bubbles in pulmonary vasculature leads to edema, hemorrhages, and respiratory distress
- Bubbles in CNS lead to mental impairment, and possible coma
Due to increased amounts of gas (nitrogen)
What is the mortality rate of amniotic fluid embolism?
80%
How does amniotic fluid embolism take place? (basic)
- Mechanical obstruction of pulmonary vessels
- Biochemical activation of coagulation pathway and innate immune system due to substances in amniotic fluid
How does amniotic fluid embolism take place? (detailed)
- Tears of placental membrane or uterine vein lead to entry of amniotic fluid into maternal circulation
- Amniotic fluid embolize into pulmonary arterioles increasing pulmonary arterial pressure causing right HF and pulmonary edema
- Procoagulants (e.g., thromboplastin enter maternal circulation activating the coagulation cascade leading to DIC and systemic fibrin thrombi
- Entry of leukotrienes from amniotic fluid into maternal circulation trigger an anaphylactic-like response leading to pulmonary edema and hypotension
What type of necrosis is noted by ischemic events of the CNS?
Liquefactive necrosis
In most tissues (except for the brain), the main histologic finding (type of necrosis), is?
Coagulative necrosis
Give (2) organs as an example of dual supply that helps minimize the effects of vascular occlusion.
- Liver: hepatic artery & portal vein
- Pulmonary system: pulmonary arterioles and bronchioles supply
How long does the CNS have regarding hypoxic events to minimize irreversible damage?
3-4 mins
How long can myocardial cells survive an ischemic event?
20-30 mins
