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Pathology > Hemostasis and Related Disorders > Flashcards

Hemostasis and Related Disorders Flashcards

1
Q

What is step 1 of primary hemostasis?

A

Step one is transient vasoconstriction of the damaged vessel.

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2
Q

Transient vasoconstriction of the damaged vessel in step one of primary hemostasis is mediated by what two factors?

A

Reflex neural stimulation and endothelium release from endothelial cells.

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3
Q

What is step two of primary hemostasis?

A

Step two is platelet adhesion to the surface of the disrupted vessel.

vWF binds exposed sub endothelial collagen, then platelets bind vWF using the GPIb receptor.

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4
Q

What is the source of Von Willebrand factor (vWF) in step two of primary hemostasis?

A

The primary source is the Weible-Palade bodies of endothelial cells, but they are also derived from the a-granules of platelets.

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5
Q

What is step three of primary hemostasis?

A

Step three is the degranulation of platelets. This is induced by adhesion and involves the release of many mediators.

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6
Q

What is step four of primary hemostasis?

A

Step 4 is platelet aggregation at the site of the injury via a fibrinogen linking molecule. This results in the formation of a weak platelet plug.

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7
Q

Describe the role of vWF in primary hemostasis.

A

vWF binds exposed sub endothelial collagen. Platelets can then bind to vWF using the GPIb receptor. Therefore vWF enables platelet adhesion to the surface of the disrupted vessel.

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8
Q

What is a Weibel-Palade body and what are its two most important sub-components?

A

Weibel-Palade bodies are the storage granules of endothelial cells. They store and release two primary molecules: von Willebrand factor and p-selectin.

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9
Q

What is the role of ADP, GPIIb, GPIIIa, and fibrinogen in primary hemostasis?

A

Platelet adhesion to the surface of the disrupted vessels induces shape change and degranulation. ADP is one of the mediators released and promotes exposure of GPIIb and GPIIIa receptors on platelets. Platelets can then aggregate at the site of injury using the GPIIb and GPIIIa receptors and fibrinogen as a linking molecule. The entire process results in the formation of a weak platelet plug.

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10
Q

What is the role of COX (platelet cyclooxygenase) and TXA2 (thromboxane A2) in primary hemostasis?

A

Platelet cyclooxegenase (COX) synthesizes thromboxane A2 (TXA2), which promotes platelet aggregation at the site of the injury.

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11
Q

What are the clinical features of disorders of primary hemostasis?

A

Mucosal and skin bleeding.

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12
Q

What are the symptoms of mucosal bleeding as a clinical feature of disorders of primary hemostasis?

A

Epistaxis (most common overall), hemoptysis, GI bleeding, hematuria, menorrhagia. The most trouble symptom is intracranial bleeding with severe thrombocytopenia.

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13
Q

What are the symptoms of skin bleeding as a clinical feature of disorders of primary hemostasis?

A

Petechiae (1-2 mm), purpura (>3mm), ecchymoses (>1cm), and easy bruising. Petechiae typically occur only in quantitative disorders.

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14
Q

What are useful laboratory studies in diagnosing/evaluating disorders of primary hemostasis?

A

Platelet count- normal 150-400 K/uL, less than 50 results in symptoms.

Bleeding time- normal 2-7 minutes, prolonged with all types of platelet disorders.

Blood smear to assess number and size of platelets.

Bone marrow biopsy used to assess megakaryocytes, which produce platelets.

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15
Q

Describe immune thrombocytopenic purpura (ITP).

A

ITP is the autoimmune production of IgG against platelet antigens (e.x. GPIIb/IIIa). It is the most common cause of thrombocytopenia in children and adults.

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16
Q

How does immune thrombocytopenic purpura (ITP) cause thrombocytopenia?

A

Antibody-bound platelets are consumed by splenic macrophages. The autoantibodies are also produced in the spleen.

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17
Q

What is acute immune thrombocytopenic purpura (ITP)?

A

The form arising in children weeks after a viral infection or immunization. It is self-limited, and usually resolved within weeks of presentation.

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18
Q

What is chronic immune thrombocytopenic purpura (ITP)?

A

The form arising in adults (typically women of child-bearing age). Can be primary or secondary. Can cause short-lived thrombocytopenia in offspring due to the ability of IgG to cross the placenta.

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19
Q

What are the laboratory findings indicative of immune thrombocytopenic purpura (ITP)?

A

A decreased platelet count, often

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20
Q

What is the initial treatment of immune thrombocytopenic purpura (ITP) and how do children and adults respond differently?

A

Initial treatment is corticosteroids; children respond well but adults may relapse after an early response.

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21
Q

What is the use of IVIG (IV immunoglobulin) in treatment of symptomatic bleeding in immune thrombocytopenic purpura (ITP) patients? What is the mechanism of this treatment?

A

IVIG is used to raise the platelet count in symptomatic bleeding. It essentially functions by giving splenic macrophages another target.

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22
Q

How does a splenectomy contribute to the treatment of patients with immune thrombocytopenic purpura (ITP)?

A

It eliminates the primary source of antibody production, as well as the site of platelet destruction. It is usually performed in refractory cases.

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23
Q

What is microangiopathic hemolytic anemia?

A

The pathological formation of platelet microthrombi in small vessels. The microthrombi shear red blood cells as they cross, resulting in hemolytic anemia with schistocytes.

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24
Q

What is a shistocyte? How are they created?

A

A schistocyte is an irregular fragment of a red blood cell, typically with two pointed ends. They are formed as red blood cells are sheared crossing microthrombi.

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25
Q

Microangiopathic hemolytic anemia is seen in which two conditions?

A

Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS).

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26
Q

Why is microangiopathic hemolytic anemia a feature of thrombotic thrombocytopenic purpura (TTP)?

A

TTP is caused by decreased ADAMTS13, an enzyme that normally cleaves vWF multimers for eventual degradation. The decreased ADAMTS13 results in large uncleaved multimers leading to abnormal platelet adhesion and microthrombi.

Decreased ADAMTS13 is usually seen in adult females as a result of an acquired antibody.

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27
Q

What is the normal role of ADAMTS13 and what is the cause of deficiencies resulting in TTP?

A

TTP is caused by decreased ADAMTS13, an enzyme that normally cleaves vWF multimers for eventual degradation. The decreased ADAMTS13 results in large uncleaved multimers leading to abnormal platelet adhesion and microthrombi.

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28
Q

What are the causes of hemolytic uremic syndrome (HUS)?

A

HUS is due to endothelial damage from drugs or infection. Classically seen in children with E. coli O157:H7 dysentery resulting from exposure to undercooked beef. The E. coli verotoxin damages endothelial cells, resulting in platelet microthrombi.

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29
Q

How does hemolytic uremic syndrome (HUS) result in microangiopathic hemolytic anemia?

A

The E. coli verotoxin damages endothelial cells, resulting in platelet microthrombi.

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30
Q

What are the clinical findings of hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP)?

A

Skin and mucosal bleeding, microangiopathic hemolytic anemia, fever, renal insufficiency (more common in HUS), and CNS abnormalities (more common in TTP).

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31
Q

What are the laboratory findings of hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP)?

A

Thrombocytopenia with increased bleeding time, normal PT/PTT, anemia with schistocytes, and increased megakaryocytes on bone marrow biopsy.

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32
Q

What is the clinical differentiation between hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP)?

A

Renal insufficiency is more common in HUS, while CNS abnormalities are more common in TTP.

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33
Q

What is the treatment for hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP)?

A

Plasmapheresis and corticosteroids, especially for TTP.

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34
Q

What are examples of qualitative disorders of primary hemostasis?

A

Bernard-Soulier syndrome, Glanzmann thrombasthenia, aspirin, and uremia.

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35
Q

Describe Bernard-Soulier syndrome and its mechanism.

A

Bernard-Soulier syndrome causes impaired platelet adhesion due to a genetic GPIb deficiency.

A blood smear would show mild thrombocytopenia with enlarged platelets.

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36
Q

Describe Glanzmann thrombasthenia and its mechanism.

A

Impaired platelet aggregation due to a genetic GPIIb/GPIIIa deficiency.

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37
Q

How can aspirin cause a qualitative primary hemostatic disorder?

A

Aspirin irreversibly inactivates cyclooxegenase; the lack of TXA2 impairs platelet aggregation.

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38
Q

How can uremia cause a qualitative primary hemostatic disorder?

A

Uremia disrupts platelet function; both adhesion and aggregation are impaired.

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39
Q

What are the two stages of hemostasis?

A

Primary hemostasis, which is the creation of a weak platelet plug. This is followed by secondary hemostasis, which is the stabilization of the platelet plug via the coagulation cascade.

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40
Q

What is secondary hemostasis?

A

In secondary hemostasis the weak platelet plug created in primary hemostasis is stabilized via the coagulation cascade.

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41
Q

What is the most important end product of the coagulation cascade? What is its role?

A

Thrombin, which converts fibrinogen in the platelet plug to fibrin. Fibrin is then cross-linked, yielding a stable platelet-fibrin thrombus.

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42
Q

What is the role of fibrinogen/fibrin in secondary hemostasis?

A

Thrombin converts fibrinogen in the platelet plug to fibrin. Fibrin is then cross-linked, yielding a stable platelet-fibrin thrombus.

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43
Q

Where are the factors of secondary hemostasis produced, where can they be found normally, and in what state?

A

They are produced in the liver in an inactive state.

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44
Q

What four substances activate the factors of the coagulation cascade to allow normal secondary hemostasis?

A

Tissue thromboplastin activates factor VII (extrinsic pathway). Subendothelial collagen activates factor XII (intrinsic pathway). The phospholipid surface of platelets and calcium (derived from platelet dense granules) are also required.

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45
Q

Factor VII and Factor XII are activated by different substances and different pathways. Describe the difference.

A

Tissue thromboplastin activates factor VII (extrinsic pathway). Subendothelial collagen activates factor XII (intrinsic pathway).

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46
Q

What is the typical cause of disorders of secondary hemostasis?

A

Factor abnormalities.

47
Q

What are the clinical features of disorders of secondary hemostasis?

A

Deep tissue bleeding into muscles and joints (hemarthrosis) and rebleeding after surgical procedures (such as circumcision and wisdom tooth extraction).

48
Q

What laboratory studies are used to diagnose disorders of secondary hemostasis?

A

Prothrombin time (PT) - measures extrinsic (factor VII) and common (factors II, V, X, and fibrinogen) pathways of the coagulation cascade.

Partial thromboplastin time (PTT) - measures intrinsic (factors XII, XI, IX, VIII) and common (factors II, V, X, and fibrinogen) pathways of the coagulation cascade.

49
Q

What is hemophilia A? Describe its mechanism and effect.

A

Hemophilia A is a genetic factor VIII deficiency. It is x-linked recessive, meaning it predominantly affects males. It can also arise de novo.

50
Q

What are the clinical findings of hemophilia A?

A

Presents with deep tissue, joint, and post surgical bleeding. The clinical severity depends on the degree of deficiency.

51
Q

What are the laboratory findings of hemophilia A?

A

Increased partial thromboplastin time (PTT) with a normal prothrombin time (PT) because PTT measures intrinsic factors including FVIII.

Decreased FVIII.

Normal platelet count and bleeding time.

52
Q

What is hemophilia B, and how is it distinguished from hemophilia A?

A

Hemophilia B is a genetic factor IX deficiency. It resembles Hemophilia A but with decreased FIX as opposed to decreased FVIII.

53
Q

What is coagulation factor inhibitor? Describe its mechanism.

A

Coagulation factor inhibitor is an acquired antibody against a coagulation factor, resulting in impaired factor function. The most common is anti-FVIII.

54
Q

What are the clinical findings of coagulation factor inhibitor?

A

They are similar to hemophilia A; deep tissue, joint, and post surgical bleeding.

55
Q

What are the laboratory findings of coagulation factor inhibitor? How do they differ from hemophilia A?

A

They are similar to hemophilia A, with the exception of the partial thromboplastin time. PTT does not correct when you mix normal plasma with the patients plasma due to the antibody. The mixing test does correct PTT in hemophilia A.

56
Q

What is Von Willebrand disease? Describe the mechanism.

A

Von Willebrand disease is a genetic deficiency of vWF. Low vWF impairs platelet adhesion. It’s the most common inherited coagulation disorder.

57
Q

What is the most common subtype of Von Willebrand disease?

A

There are multiple subtypes that cause both quantitative and qualitative defects. Most common type is autosomal dominant with decreased vWF levels.

58
Q

What are the clinical findings of Von Willebrand disease?

A

Mild mucosal and skin bleeding.

59
Q

What are the laboratory findings of Von Willebrand disease?

A

Increased bleeding time.

Increased PTT, normal PT. this is caused by the decreased FVIII half-life, which is normally stabilized by vWF.

Abnormal ristocetin tests.

60
Q

Hemophilia A and Von Willebrand disease both involve factor VIII abnormalities; how do they differ with respect to bleeding? Why?

A

The deep tissue, joint, and post surgical bleeding that are common features of Hemophilia A are not typically seen with Von Willebrand disease. This is because hemophilia A is a FVIII deficiency. Von Willebrand disease is a deficiency in vWF, which stabilizes FVIII. Thus in Von Willebrand disease the FVIII is still able to function in spite of reduced half-time, which prevents the typical bleeding patterns of hemophilia A.

61
Q

What is a ristocetin test and how is it used to diagnose Von Willebrand disease?

A

Ristocetin is a substance that induces platelet agglutination by causing vWF to bind platelets via the GPIb receptors on the platelet. YA lack of vWF leads to impaired agglutination, which leads to an abnormal test.

62
Q

How is Von Willebrand disease treated?

A

Treatment is desmopressin, an ADH analog. This increases vWF release from the Weibel-Palade bodies of endothelial cells.

63
Q

How does Vitamin K disrupt coagulation factors and cause disorders of secondary hemostasis?

A

Normally Vitamin K is activated by epoxide reductase in the liver. The activated form of Vitamin K gamma carboxylates factors II, VII, IX, X, and proteins C and S. Gamma carboxylation is necessary for factor function.

64
Q

Describe the three most common mechanisms of Vitamin K deficiency.

A

Newborns: due to a lack of GI colonization by bacteria that normally synthesize vitamin K. For this reason a vitamin K injection is given prophylactically to all newborns at birth to prevent hemorrhagic disease of the newborn.

Long-term antibiotic therapy: disrupts vitamin K producing bacteria in the GI tract

Malabsorption: leads to deficiency of fat-soluble vitamins, including vitamin K.

65
Q

How can liver failure result in abnormal secondary hemostasis?

A

Coagulation factors are produced in the liver, and Vitamin K is activated in the liver. Liver failure prevents activation of coagulation factors via vitamin K, and production of those factors in the first place.

You can track the effect of liver failure on coagulation using PT.

66
Q

How can a large-volume transfusion result in abnormal secondary hemostasis?

A

Coagulation factors are diluted during the transfusion, resulting in a relative deficiency.

67
Q

What is heparin-induced thrombocytopenia? What is the most serious potential consequence?

A

It is platelet destruction that arises secondary to heparin therapy.

Fragments of destroyed platelets may activate remaining platelets, leading to thrombosis.

68
Q

What is disseminated intravascular coagulation?

A

Disseminated Intravascular Coagulation is the pathologic activation of the coagulation cascade. This results in widespread microthrombi leading to ischemia and infarction.

This consumption of platelets and factors results in bleeding, especially from IV sites and mucosal surfaces (orifices).

69
Q

Disseminated intravascular coagulation is almost always secondary to another disease process. What are some of the most common?

A

Obstetric complications, sepsis, adenocarcinoma, acute promyelocytic leukemia, and rattlesnake bites.

70
Q

How do obstetric complications lead to disseminated intravascular coagulation?

A

Tissue thromboplastin in the amniotic fluid activates pathologic coagulation.

71
Q

How does sepsis (especially with E. coli or N. meningitidis) contribute to disseminated intravascular coagulation?

A

Endotoxins from the bacterial wall and cytokines (e.g. TNF and IL-1) induce endothelial cells to make tissue factor.

72
Q

How does adenocarcinoma contribute to disseminated intravascular coagulation?

A

Mucin activates coagulation.

73
Q

How does acute promyelocytic leukemia contribute to disseminated intravascular coagulation?

A

Primary granules activate coagulation.

74
Q

How do rattlesnake bites contribute to disseminated intravascular coagulation?

A

Venom activates coagulation.

75
Q

What are the laboratory findings of disseminated intravascular coagulation?

A
  • Decreased platelet count.
  • Increased PT/PTT.
  • Decreased fibrinogen.
  • Microangiopathic hemolytic anemia.
  • Products of splitting of cross-linked fibrin, particularly D-dimer. The elevated D-dimer is the best screening test for DIC.
76
Q

What is the treatment for disseminated intravascular coagulation?

A

Treatment involves addressing the underlying cause and transfusing blood products and cryoprecipitate (containing coagulation factors) as necessary.

77
Q

What is the function of normal fibrinolysis?

A

Normal fibrinolysis removes thrombus after damaged vessel heals.

78
Q

Describe the process of normal fibrinolysis.

A

Tissue plasminogen activator (tPA) converts plasminogen to plasmin.

Plasmin cleaves fibrin and serum fibrinogen, destroys coagulation factors, and blocks platelet aggregation.

a2-antiplasmin inactivates plasmin.

79
Q

What is the mechanism of disorders of fibrinolysis?

A

Plasmin overactivity resulting in excessive cleavage of serum fibrinogen.

80
Q

How does a radical prostatectomy result in a disorder of fibrinolysis?

A

The release of urokinase activates plasmin.

81
Q

How does cirrhosis of the liver result in disorders of fibrinolysis?

A

Reduced production of a2-antiplasmin.

82
Q

What are the clinical findings of disorders of fibrinolysis?

A

Increased bleeding resembling disseminated intravascular coagulation.

83
Q

What are the laboratory findings of disorders of fibrinolysis?

A

Increased PT/PTT - plasmin destroys coagulation factors.

Increased bleeding time with normal platelet count. Plasmin blocks platelet aggregation.

Increased fibrinogen split products without d-dimers. Serum fibrinogen is lysed but d-diner is not formed because fibrin thrombi are absent.

84
Q

Why aren’t d-diners formed in disorders of fibrinolysis?

A

Fibrin thrombi are absent.

85
Q

What is the treatment for disorders of fibrinolysis?

A

Aminocaproic acid, which blocks activation of plasminogen.

86
Q

What is a thrombosis, including its most common location?

A

A thrombosis is a pathologic formation of an intravascular blood clot (a thrombus). This can occur in an artery or vein, but the most common location is the deep veins of the leg below the knee (DVT).

87
Q

What features characterize a thrombosis (distinguishing it from a postmortem clot)?

A
  1. Lines of zahn (alternating layers of platelets/fibrin and RBCs)
  2. Attachment to a vessel wall
88
Q

What are the three major risk factors for thrombosis?

A

Disruption in blood flow, endothelial cell damage, and hypercoagulable state.

These three are referred to as Virchow’s Triad.

89
Q

How do immobilization, cardiac wall dysfunction, and/or an aneurysm increase risk for thrombosis?

A

Stasis and turbulence of blood flow increases risk for thrombosis. Normal blood flow is continuous and laminar, which keeps platelets and factors dispersed and inactivated.

Immobilization increases risk for deep venous thrombosis (DVT) via stasis.

Cardiac wall dysfunction (such as an arrhythmia or myocardial infarction) creates turbulent or even static blood flow.

Aneurysm.

90
Q

How does endothelial cell damage increase the risk for thrombosis?

A

Damage disrupts the protective function of endothelial cells.

91
Q

Describe the mechanisms by which endothelial cells prevent thrombosis.

A
  1. Endothelial cells block exposure to subendothelial collagen and underlying tissue factor.
  2. Endothelial cells produce prostacyclin (PGI2) and NO, which cause vasodilation and inhibition of platelet aggregation.
  3. Endothelial cells secrete heparin-like molecules augmenting antithrombin III (ATIII) which inactivates thrombin and coagulation factors.
  4. Endothelial cells secrete tissue plasminogen activator (tPA), which converts plasminogen to plasmin.

Plasmin cleaves fibrin and serum fibrinogen, destroys coagulation factors, and blocks platelet aggregation.

  1. Endothelial cells secrete thrombomodulin. Thrombomodulin redirects thrombin to activate protein C, which inactivates factors V and VIII.
92
Q

What are the three common causes of endothelial cell damage?

A

Atherosclerosis, vasculitis, and high levels of homocysteine.

93
Q

How do vitamin B12 and/or folate deficiencies result in endothelial cell damage?

A

Deficiency results in mildly elevated homocysteine levels, increasing risk for thrombosis.

Folic acid circulates as methyl-THF in the serum.

Methyl is transferred to vitamin b12, allowing THF to participate in synthesis of DNA precursors.

Vitamin B12 transfers methyl to homocysteine, resulting in methionine.

Lack of vitamin B12 or folate leads to decreased conversion of homocysteine to methionine, resulting in a buildup of homocysteine.

94
Q

How does cystathionine beta synthase (CBS) result in endothelial cell damage?

A

Cystathionine beta synthase (CBS) deficiency results in high homocysteine levels with homocystinuria.

CBS converts homocysteine to cystathionine; the enzyme deficiency leads to homocysteine buildup.

It is characterized by vessel thrombosis, mental retardation, lens dislocation, and long slender fingers.

95
Q

What is a hypercoagulable state?

A

An excessive tendency towards coagulation due to excessive procoagulant proteins or defective anticoagulant proteins. It can be inherited or acquired.

96
Q

What is the classic presentation of a hypercoagulable state?

A

Recurrent DVTs or DVT at a young age. Typically occurs in the deep veins of the leg, but other sites include hepatic and cerebral veins.

97
Q

How does autosomal dominant protein C or S deficiency result in a hypercoagulable state? How does this relate to warfarin therapy?

A

Protein C or S deficiency decreases negative feedback on the coagulation cascade. These proteins normally inactivate factors V and VIII.

The initial stages of warfarin therapy result in a temporary deficiency of proteins C and S (due a shorter half-life) relative to factors II, VII, IX, and X.

If there’s a preexisting deficiency of proteins C or S, a severe deficiency at the start of warfarin therapy results in warfarin skin necrosis and increased risk for thrombosis.

98
Q

What is Factor V Leiden, and how does it create a hypercoagulable state?

A

Factor V Leiden is a mutated form of factor V that lacks the cleavage site for deactivation by proteins C and S. This is the most common inherited cause of a hypercoagulable state.

99
Q

What is prothrombin 20210A, and how does it result in a hypercoagulable state?

A

Prothrombin 20210A is an inherited point mutation in prothrombin that results in increased gene expression.

Increased prothrombin results in increased thrombin, promoting thrombus formation.

100
Q

What is ATIII, and how does it contribute to a hypercoagulable state?

A

ATIII is a molecule that inactivates thrombin and coagulation factors.

ATIII deficiency decreases the protective effect of heparin-like molecules produced by the endothelium, which in turn increases the risk for thrombus. Those heparin-like molecules normally activate ATIII.

101
Q

How do oral contraceptives (estrogen) contribute to a hypercoagulable state?

A

Estrogen induces increased production of coagulation factors, thereby increasing the risk for thrombus.

102
Q

What is an embolism, and what is the most common type?

A

An embolism is an intravascular mass that travels and occluded downstream vessels. Symptoms will depend on the vessel involved.

The most common type is a thromboembolus (>95%), which is caused by a thrombus that dislodges.

103
Q

Describe an atherosclerotic embolus.

A

An atherosclerotic embolus is due to an atherosclerotic plaque that dislodges.

It is characterized by the presence of cholesterol clefts in the embolus.

104
Q

Describe a fat embolus.

A

Fat embolus is associated with bone fractures, particularly long bones, and soft tissue trauma.

It develops while the fracture is still present or shortly after repair.

Characterized by dyspnea (fat, often with bone marrow elements, is seen in pulmonary vessels) and petechiae on the skin overlying the chest.

105
Q

Describe a gas embolus, including decompression sickness, Caisson disease, and incidents during laparoscopic surgery.

A

Decompression sickness creates a gas embolus when as nitrogen gas precipitates out of blood due to rapid ascent by a diver. This presents with joint and muscle pains (bends) and respiratory symptoms (chokes).

Caisson disease, the chronic form of decompression sickness, is characterized by multifocal ischemic necrosis of bone.

Laparoscopic surgery can result in a gas embolus after air is pumped into the abdomen.

106
Q

Describe the features of an amniotic fluid embolus that has entered the maternal circulation.

A

An amniotic fluid embolus enters maternal circulation during labor or delivery.

It presents with shortness of breath, neurological symptoms, and DIC (due to the thrombogenic nature of amniotic fluid).

It’s characterized by squamous cells and keratin debris, from fetal skin, in embolus.

107
Q

Describe a pulmonary embolism, including the most common cause.

A

A pulmonary embolus is an obstruction that has traveled to the vessels of the lung.

It is usually caused by a thromboembolus. The most common source is a DVT of the lower extremity (especially the femoral, iliac, or popliteal veins).

108
Q

Why is a pulmonary embolism usually clinically silent?

A
  1. The lung has a dual blood supply (via the pulmonary and bronchial arteries).
  2. The embolus is usually small (self-resolves).
109
Q

When does a pulmonary embolism progress to a pulmonary infarction?

A

If a large- or medium-sized artery is obstructed in patients with pre-existing cardiopulmonary compromise.

Only 10% of PEs cause infarction.

110
Q

What are the clinical findings of a pulmonary infarction?

A

Shortness of breath
Hemoptysis
Pleuritic chest pain
Pleural effusion

111
Q

What are the laboratory and/or imaging findings in a pulmonary infarction?

A

V/Q lung scan shows mismatch; perfusion is abnormal.

Spiral CT shows a vascular filling defect in the lung.

Lower extremity Doppler ultrasound is useful to detect DVT.

D-dimer is elevated.

Gross examination reveals a hemorrhagic, wedge shaped infarct.

112
Q

When does a pulmonary infarction result in death?

A

When a large saddle embolus blocks both left and right pulmonary arteries, or with significant occlusion of a large pulmonary artery.

Death is due to electromechanical dissociation.

113
Q

How is pulmonary hypertension related to emboli?

A

Pulmonary hypertension may arise with chronic emboli that are reorganized over time.

114
Q

What is a systemic embolism? What is the most common cause and location?

A

An embolism that travels down the systemic circulation to occlude flow to organs, most commonly the lower extremities.

It is usually due to a thromboembolus.

It most commonly arises in the left heart.

Pathology (19 decks)

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