Exam #2: Hemodynamics IV

Question 1

What is Virchow’s Triad?

Answer 1

Virchow’s Triad outlines the three primary abnormalities that lead to thrombus formation:

1) Endothelial Injury
2) Stasis
3) Hypercoaguable state

Question 2

What is the dominant influence on thrombosis formation?

Answer 2

Endothelial injury

Question 3

Why is endothelial injury especially important for thrombus formation in the heart & arterial circulation?

Answer 3

High flow rates impede platelet adhesion & washout clotting factors; thus, endothelial injury is the major factor leading to thrombus formation in these high flow areas

Question 4

List the difference sources of endotheial injury & dysfunction.

Answer 4

1) DM
2) HTN
3) Smoking
4) Oxidtive stress
5) LDL cholesterol
6) Homocysteine ADMA

Question 5

List the consequences of endothelial dysfunction.

Answer 5

1) Vasoconstriction
2) Increased leukocyte adhesion & infiltration
3) Platelet aggregation & thrombosis
4) Vascular smooth muscle cell proliferation
5) Lipid accumulation

Question 6

What is the difference between primary and secondary hypercoaguable states?

Answer 6

Primary= genetic mutation leading to hypercoagulation
- Factor V Leiden

Secondary= acquired alterations leading to hypercoagulation i.e.

• stasis
• bed rest

Question 7

What is a Factor V Leiden deficiency?

Answer 7

• Factor V is a clotting factor
• Normally broken down by protein C
• Mutation in Factor V prevents the removal of Factor V by protein C–>hypercoaguable state

Specifically, a glutamine residue is substituted for arginine in the 506 position, and prevents cleavage by protein C

Question 8

What is the typical presentation of Factor V Leiden deficiency?

Answer 8

Recurrent DVTs without secondary risk factors

- More common in caucasians

Question 9

What is antiphospholipid antibody syndrome?

Answer 9

Serum antibody directed against anionic phospholipid

• In vitro there is INHIBITION of clotting due to interference with assembly of phospholipid complexes
• In vivo= HYPERCOAGUABLE state

Question 10

What is antiphospholipid antibody syndrome associated with?

Answer 10

Autoimmune diseases, especially, SLE

Question 11

What are the clinical manifestations of antiphospholipid antibody syndrome?

Answer 11

• Recurrent venous or arterial thrombi
• Repeated miscarriage
• Cardiac valve vegetations
• Thrombocytopenia

Question 12

What is the effect of turbulence in the vasculature?

Answer 12

Disruption of normal laminar flow

• In normal laminar flow, platelets flow centrally & are separated from the endothelium by slower moving plasma
• Stasis & turbulence:

1) Disrupts laminar flow & brings platelets in contact with endothelium
2) Prevents dilution of clotting factors
3) Promotes endothelial cell activation

Question 13

List the causes of turbulence in the vasculature?

Answer 13

• Ulcerated atherosclerotic plaque
• Aneurysms
• MI
• Mitral valve stenosis
• Hyperviscosity syndrome i.e. polycythemia
• Sickle cell anemia

Question 14

Describe the morphology of thrombi. What is the difference between aterial & venous thrombi?

Answer 14

Arterial= usually occur at sites of endothelial cell injury
- Grey-white and friable

Venous= more commonly caused by stasis/ low-flow
- Red, slower blood flow= higher accumulation of RBCs

Question 15

What are the complications of arterial thrombi?

Answer 15

May cause local obstruction or distant embolization leading CVA, MI, and PAD

Risk Factors

• MI
• Rheumatic heart disease
• A-fib
• Atherosclerosis

Question 16

What are arterial thrombi composed of?

Answer 16

Platelets
Fibrin
Erythrocyte
Leukocytes

Question 17

Describe the relative incidence of arterial thrombi i.e. where do they occur most commonly?

Answer 17

Coronary arteries
Cerebral arteries
Femoral arteries

Question 18

Where does rupture of a thrombis typically occur?

Answer 18

“Shoulder region”

Question 19

What is an abdominal aortic aneurysm?

Answer 19

Outpouching of the wall of the abdominal aorta that is at risk for rupture
- Layered thrombus is in the lumen

Question 20

What are “Lines of Zahn?”

Answer 20

Alternating layering of pale platelets & fibrin with darker erythrocytes

*****Note that these are important for distinguishing between antemortem & postmortem thrombosis

Question 21

Where are venous thrombi most commonly seen?

Answer 21

90% involve LE veins, but other less common sites include:

UE
Periprostatic plexus
Ovarian & periuterine veins

Question 22

Where do venous thrombi typically form?

Answer 22

In valve pockets of the deep veins

Question 23

What is phlebothrombosis?

Answer 23

Superficial thrombi that rarely embolize

Question 24

In what percentage of patients are DVTs asymptomatic?

Answer 24

50%

**This is important! In roughly 50% of affect patients, collateral circulation may mask symptoms of a DVT i.e. the patient is asymptomatic.

Question 25

What are the risk factors for venous thrombosis?

Answer 25

``` CHF Trauma Surgery Pregnancy Cancer ```

Question 26

What is Trousseau Syndrome?

Answer 26

This is a "migrating thrombophlebitis" caused by a serine protease released by malignant tumors that activates Factor X - Tumor cells release plasma membrane vesicles exhibiting procoagulant activity - Tissue thromboplastin is released from a necrotic tumor e

Question 27

What are the different fates of a thrombus?

Answer 27

1) Resolution 2) Embolization 3) Organization and incorporation into the wall 4) Organization & recannulization

Question 28

What is an embolus?

Answer 28

A detached intravascular solid, liquid, or gas that is carried by the blood to a distant site from its point or origin - Lodge is vessels that are too small for migration to continue - Unless otherwise specified, embolus is assumed to be a "THROMBOEMBOLUS"

Question 29

List the sources of aterial emboli.

Answer 29

- A-fib - Mitral stenosis - Endocarditis - Mural thrombi in heart or aorta* - Paradoxical emboli

Question 30

What is the most common source of emboli that migrate within the arterial circulation?

Answer 30

Intracardiac mural thrombi

Question 31

What is a paradoxical emboli?

Answer 31

Rare condition in which an embolus originating from the VENOUS circulation passes through a VSD and into the systemic circulation E.g. a DVT that causes a stroke

Question 32

What is the most common cause of a pulmonary thromboembolism?

Answer 32

95% arise from deep leg vein thrombi ABOVE THE KNEE

Question 33

Where can a pulmonary thromboembolism occlude?

Answer 33

- Main pulmonary artery - Saddle= across vessel bifurcation - Smaller braching arterioles *Can cause sudden death via acute RVH

Question 34

What is cor pulmonale?

Answer 34

Chronic/ recurrent pulmonary embolism that leads to pulmonary HTN

Question 35

How are pulmonary embolism diagnosed?

Answer 35

- 2D echo - V/Q scan - CT chest - MRI - Venogram

Question 36

What causes a fat embolism?

Answer 36

Long bones contain fatty marrow. In 90% of long bone fractures/ skeletal trauma, there is embolism of this fatty marrow, leading to a fat embolism. However, on 10% of patients actually develop clinical findings i.e. most are ASYMPTOMATIC

Question 37

What is fat embolism syndrome?

Answer 37

This is the term applied to the minority of patients with a fat embolism that become symptomatic. Typically 1-3 s/p injury: 1) Dyspnea, tachypnea, & tachycardia 2) Irritability & restlessness 3) Progression to delirium & coma

Question 38

What is an air embolism?

Answer 38

Coalesced gas bubbles in the circulation-->obstruction of vascular flow

Question 39

Outline the pathophysiology of decompression sickness or the Bends.

Answer 39

- Sudden change in atmospheric pressure i.e. diving - Nitrogen inspired at high pressure (deep under water) dissolves in blood - Rapid decrease in pressure i.e. rapid ascent, nitrogen comes out of solution & forms gas bubbles in the circulation

Question 40

What is the difference between "the bends" and "the chokes?"

Answer 40

Bends= dissolution of nitrogen in muscles, bones, and joints leads to a painful condition called, "the bends" Chokes= dissolution of nitrogen in the lung vasculature leading to edema, hemorrhage, and focal atelectasis-->respiratory distress

Question 41

What is the treatment for decompression sickness?

Answer 41

Hyperbaric oxygen therapy= - Forces gas back into solution - Allows for slow & controlled decompression

Question 42

What is an amniotic fluid embolism?

Answer 42

Breach of the placental membranes & uterine veins causes infusion of amniotic fluid into maternal circulation. This is a very ominous diagnosis and leads to: - Sudden severe dyspnea - Cyanosis - Shock - Neurologic impairment (headache, seizures-->coma) IF the patient survives the initial crisis, pulmonary edema and DIC follow.

Question 43

Describe the pathophysiology of an amniotic fluid embolism.

Answer 43

Tear in the placental membranes or rupture of the uterine veins leads to amniotic fluid or fetal tissue into the maternal circulation

Question 44

List the contents of an amniotic fluid embolism. What is important about the contents?

Answer 44

Squamous cells from fetal skin Lanugo hair Fat from vernix caseosa Mucin from fetal respiratory or GI tract *****All are procoagulative

Question 45

What is the definition of infarction?

Answer 45

Death of tissue due to the interruption in blood supply

Question 46

What can cause infarction besides thrombosis & emboli?

Answer 46

- Vasopasm e.g. cocaine-->MI - Hemorrhage within athersclerotic plaque - Extrinsic compression of vessel - Twisting of a vessel e.g. testicular torsion or intestinal volvulus

Question 47

What is the major factor in tissue damage from infarction?

Answer 47

Availability of alternative blood supply

Question 48

What cells are the most vulnerable to hypoxia?

Answer 48

``` Neurons= 3-4 min Myocardium= 20-30 min Fibroblasts= Hours ```

Question 49

Describe the general morphology of an infarct.

Answer 49

- Wedge-shaped - Poorly defined - Over time delineated by a rim of hyperemia

Question 50

What is the difference between a red and white infarct?

Answer 50

``` Red= venous occlusion White= arterial occlusion ```