Lectures 1-4 - Cardiovascular Pathophysiology I-IV Flashcards
What are the 3 layers of a vessel wall? List from outer to inner. What to note?
- Tunica intima
- Tunica media
- Tunica adventitia
NOTE: structure of the wall varies greatly between types and sizes of vessels
2 parts of tunica intima?
- Endothelium
2. BM
2 parts of tunica media?
- Smooth muscle
2. Elastic fibers
What is the tunica adventitia made of?
Areolar connective tissue
3 characteristics of vascular smooth muscle cells?
- Contractile
- Secretory: matrix, growth factors, proteases
- Plastic: hypertrophy, proliferation, large changes in phenotype
Basal state of the VSMCs?
Contractile
When are VSMCs secretory?
Usually when injured
2 factors affecting the vascular tone of the VSMCs?
- Intrinsic factors: myogenic tone
2. Extrinsic factors: neurogenic and humoral tone
What does vasomotion mean?
Change in caliber of a BV
4 roles of the endothelium in BVs?
- Barrier
- Secretory and modulatory for vascular smooth muscle tone and growth, and platelet function
- Metabolic: processing of vasoactive factors like ACE production of angiotensin II and breakdown of bradykinin (inflammation)
- Plasticity: angiogenesis in response to injury and ischemia
4 secretions of the endothelium?
- Endothelial-derived vasodilators: nitric oxide (NO) and prostacyclin (PGI2)
- Endothelial-derived vasoconstrictors: endothelin
- Anti-aggregatory for platelets
- Anti-mitogenic for vascular smooth muscle
What is flow through a region mainly governed by?
Mainly governed by the resistance of the microcirculation
What is Poiseuille’s Law?
(P1 - P2) = 8.η.L.Q / (π.r^4)
r = vessel radius η = fluid viscosity L = length of the vessel
How can turbulent flow cause BV damage?
Causes shear stress on the endothelium causes inflammation and diminished function
3 controls of local blood flow?
- Metabolic regulation through local metabolites (primarily vasodilation)
- Autoregulation through transmural pressure causing vasoconstriction
- Shear stress-induced vasodilation due to the longitudinal pressure gradient
Other name for autoregulation of local blood flow?
Myogenic regulation
Hydrostatic pressure at the beginning and end of a capillary bed?
Beginning: 32 mmHg
End: 25 mmHg
Oncotic pressure at the beginning and end of a capillary bed?
25 mmHg constant throughout
Is there a net fluid loss at capillary beds?
Not usually, but in the lower extremities the hydrostatic pressure due to gravity may favor filtration, which is usually compensated for
This can cause issues, for example during thermoregulation
In what vein does the thoracic duct drain?
Left subclavian vein
What is an edema?
Increased fluid in interstitial spaces
6 possible causes of edema? Provide examples for each.
- Increased hydrostatic pressure: impaired venous drainage or arteriolar dilation
- Decreased plasma oncotic pressure: protein-losing glomerulopathies (nephrotic syndrome), liver cirrhosis (ascites), malnutrition, protein-losing gastroenteropathy, reduced albumin
- Increased capillary permeability: burns, allergic inflammation reactions => increased tissue oncotic pressure and lymph obstruction
- Lymph obstruction: inflammation, neoplasticity, post-surgery, post-irradiation
- Sodium retention: excessive salt intake with renal insufficiency, increased tubular reabsorption of Na+, renal hypoperfusion, increased RAA secretion
- Inflammation: acute, chronic, or due to angiogenesis
5 subtypes of edema?
- Lymphedema: normally localized
- Subcutaneous edema: either regional due to heart or systemic due to kidneys
- Pulmonary edema: due to left ventricular failure or ARDS
- Brain edema: either local due to abscesses or neoplasms or generalized due to trauma
- Anasarca: extreme generalized edema
Clinical relevance of edema?
It points to an underlying disease, and is commonly associated with diminished inflammatory processes, e.g., impaired wound healing and ability to fight infection
Treatment for edema?
Albumin IV
4 possible causes of impaired venous return causing edema?
- CHF => increased central venous pressure => increased capillary pressure
- Constrictive pericarditis
- Ascites (liver cirrhosis)
- Venous obstruction or compression: thrombosis, external pressure (e.g. mass), lower extremity inactivity with prolonged dependency
2 possible causes of arteriolar dilation causing edema?
- Heat
2. Neurohumoral dysregulation
Describe the shock pathway.
Widespread vasodilation increases capacity of vascular bed => systemic hypoperfusion (due to reduced CO or circulating BV?) => hypotension => impaired tissue perfusion => cellular hypoxia (initially reversible), but if sustained => irreversible tissue injury => death
5 types of shock? Describe each.
- Cardiogenic: pump failure (intrinsic myocardial damage, ventricular arrhythmias, outflow obstruction)
- Hypovolemic: loss of blood or plasma (hemorrhage, severe burns, trauma)
- Neurogenic: anesthetic/spinal cord injury causing an imbalance between sympa and parasympa stimulation => loss of vascular tone and peripheral pooling of blood
- Anaphylactic: generalized IgE hypersensitivity => systemic vasodilation and increased vascular permeability
- Septic: systemic microbial infection (gram negative or positive endotoxins and fungal)
What is shock the common final pathway for?
Many severe events like hemorrhage, trauma, burns, myocardial infarctions, pulmonary embolism, sepsis, etc.
Describe the pathway of cardiogenic shock.
Decreased CO => RAA, ADH, catecholamine, and splenic discharge compensation => increase in BV and decrease in SVR => increased preload, SV, and HR =>
- Systemic and pulmonary edema => dyspnea
- Increased myocardial O2 requirements => decreased CO and EF => decreased BP => decreased tissue perfusion => ischemia and impaired cellular metabolsim => myocardial dysfunction => decreased CO and EF => vicious cycle
Describe the pathway of anaphylactic shock.
Allergen => IgE production => complement, histamine, kinins, prostaglandins system activation (aka inflammation) =>
- Increased capillary permeability => extravasation of intravascular fluids => edema + hypovolemia
- Peripheral vasodilation => decreased SVR => hypovolemia
- Constriction of extravascular smooth muscle => bronchoconstriction, laryngospasm, GI cramps
Hypovolemia => decreased CO => decreased tissue perfusion => impaired cellular metabolism
What is responsible for most ICU deaths?
Septic shock
Describe the pathway of septic shock.
Bacterial wall LPS released when cell walls are degraded => toxic FA core and polysaccharide coat unique to species induce an inflammatory response (cytokine cascade) =>
- Systemic vasodilation
- Increased vessel permeability
- Pump failure
- DIC
Septic shock mortality rate? What is it associated with?
25-50% mortality rate and is associated with multi-organ system failure (liver, kidneys,
CNS)
What does DIC stand for? What is it?
Disseminated intravascular coagulation = widespread activation of thrombin (coagulation factor) within the microcirculation (more so than antithrombins) causing diffuse circulatory insufficiency (brain, heart, lung, kidneys) leading to:
- Ischemia/micro infarcts
- Hemolysis
- Widespread injury to ECs
What are the 3 different exposure to LPS and their effects?
- Low: monocyte/macrophage/neutrophil activation, endothelial cell activation, complement activation => local inflammation
- Moderate: fever (brain effect), acute-phase reactants (liver effect), and lymphocytes => systemic effects
- High: low CO, low SVR, blood vessel injury, thrombosis, DIC, ARDS => septic shock
What are the 3 stages of shock?
- Nonprogressive stage
- Progressive stage
- Irreversible stage
What is hemorrhage?
Extravasation of blood due to a rupture in the vessel wall
What is a hematoma?
Blood accumulation within a tissue
How are hemorrhages classified?
By their relative size:
- Petechiae (1-2mm): minute, happen into skin, mucus or serosal membranes
- Purporas (3-5mm)
- Bruises (1-2cm): subcutaneous hematomas with RBC deposition, which are then phagocytosed by macrophages => Hb released metabolized into bilirubin which is then converted to hemosiderin (golden brown)
Other name for bruises?
Ecchymoses
Important to keep in mind with hemorrhages?
The cavity size: thorax, peritoneum, etc.
What 3 elements in the blood will lead to clot formation? What is this regulated by?
- Platelets
- Clotting factors
- Dysfunctional endothelium
Regulated by the inflammatory system (including monocytes, neutrophils, and lymphocytes)
Purpose of clot formation?
Preventing blood from moving from the intravascular space to the extravascular space
What is hemostasis?
Clot formation
What is thrombosis? What is it described by?
Clot formation as a result of dysregulation of hemostasis, described by Virchow triad:
- EC injury: perturbation of balance via hypertension, shear stress, turbulent flow, or bacterial infection
- Alterations in blood flow: turbulence and stasis (due to atherosclerotic plaques, aneurysms, MI, and mitral valve stenosis) => contact of activated platelets with EC => prevents dilution of clotting factors, retards inflow, promotes EC and platelet activation
- Hypercoagulability: contributes less frequently, yet is an important aspect comprised of genetic (V and prothrombin gene) and acquired components
Can lymphocytes and platelets spontaneously activate? How is this controlled?
YUP
Role of endothelium to keep them in check
What 6 processes may occur following thrombus formation? Describe each.
- Propagation: due to the accumulation of platelets and fibrin
- Embolization: resulting from a dislodged clot
- Dissolution: can occur with adequate fibrinolytic activity
- Organization: due to inflammation, fibrosis, and EC and SMC ingrowth, and
incorporation into the thickened vascular wall, followed by recanalization and subsequently re-establishing blood flow - Infarction: downstream results
- Hemorrhage: inability to form a proper clot => can lead to shock
How can cardiac dysfunction cause thrombi? 3 examples?
Cardiac dysfunction is often the origin of arterial thrombi with formation beginning at the site of injury (plaque) or turbulence (bifurcation), and is associated with retrograde growth
Examples include:
1. MI: dyskinetic contraction of myocardium + damage to endocardium => mural thrombus
- Rheumatic heart disease => mitral valve stenosis => left atrial dilation with atrial fibrillation => atrial blood stasis, resulting => mural thrombus
- Atherosclerosis => EC injury and abnormal blood flow
Effect of stasis on endothelial cells?
It causes them to die faster because they have reached their “quota” of platelet deactivation
How is venous stasis different from arterial stasis? What does this mean for the thrombi?
In venous blood there are many toxic waste substances, including CO2 which can be converted to H+ by carbonic anhydrase => wastes and metabolic acidosis can cause inflammation => increased work of endothelium => die faster
Venous thrombi commonly occur at sites of stasis, and extend in the direction of growth/blood flow with the propagating tail not well attached and is therefore prone to embolus, cast formation (hardening of the thrombus)
2 examples of venous thrombi?
- Superficial (varicosities) vein thrombi
2. Deep vein thrombi of the leg
What is a platelet disorder and its 2 subtypes?
Thrombocytopenia
- Immune thrombocytopenic purpura (ITP)
- Thrombotic thrombocytopenic purpura (TTP)
What is thrombocytopenia? What is it often secondary to?
- Platelet count < 100K/mm3 (normal is 300K/mm3)
- Often secondary to congenital/acquired conditions which ↓ platelet synthesis or platelet survival
What is ITP?
Autoimmune platelet destruction
What is TTP? What to note?
Platelets inappropriately activate, aggregate and occlude arterioles and capillaries
Note: usually increased interaction with Von Willebrand factor
Other name for platelets?
Thrombocytes
At what platelet count does spontaneous bleeding occur?
10-15k/mm3
What does purpura refer to?
Discoloration due to the accumulation of blood
2 types of TTP?
- Chronic relapsing
2. Acute idiopathic
Is DIC a primary disease?
NOPE
What is a consumptive coagulopathy? Example?
Multiple thrombi form causing rapid concurrent consumption of platelets and coagulation proteins
Example: DIC
What is released in DIC?
- Tissue factor by endothelium in response to activation by inflammatory cells => sets off coagulation cascade
- Thromboplastic agents = prothrombotic factors
How can DIC affect pregnancy?
During birth there is massive blood loss with the placenta causing obstetric complications
What 5 factors can induce endothelial release/activation of tissue factor?
- Cytoplasmic granules of leukemic cells
- Carcinomas
- Bacterial sepsis
- Massive tissue destruction
- Endothelial injury
Clinical relevance of DIC?
- Shock
- Hypotension
- Increase in fibrin degradation products (FDPs) (e.g. D-dimers)
Treatment for DIC?
- Treat the underlying disorder
- Anti-coagulation therapy
- Fresh frozen plasma (FFP)