Vascular Flashcards
What % of blood goes to the pulmonary circulation
9%
What % of blood goes to the artieres
20%
What % of blood is in the veins
64%
What % of blood stays in the heart
7%
What is the order of the vascular muscle wall anatomy from inside out
Tunica Intima
Tunica Media
Tunica Externa
What type of blood vessel is mostly responsible for moderating the amount of blood flow to areas of the body
Arterioles
What is arterial pressure primarily regulated by
Circulatory vessel changes (contriction/dilation)
What is the wall thickness and contents of arteries
Thick walls with more smooth muscle and elastin
What is the wall thickness and contents of veins
Thin walls with less smooth muscle and elastin
What is the purpose in the different wall structures of arteries and veins
Arteries are made to withstand high pressures whereas veins are able to adapt to low pressures and hold more blood
What is the elsatin content in ateries and veins respectively
Arteries - high elastin
Veins - low elastin (more stretchy)
What is the only artery to contain valves
Pulmonary Artery
What is the structure of the tunica intima
inner endothelial lining of the blood vessels
What is the structure of the tunica media
Middle smooth muscle layer (also contains elastin fibres)
What is the structure of the tunica externa
outer layer of connective tissue, holding vessels together
What type of valves are in veins
bicuspid
What is the glycocalyx
Negatively charged sugar proteins that coats all healthy vessels endothelium
What is the function of glycocalyx in regards to fluid dynamics
Provides intraluminal ‘oncotic’ pressure which limits the movement of fluid to the interstitial space, stopping edema
How can the glycocalyx be damaged
ischemia, hyperglycemia, inflammation, hypertension
What is the structure of large elastic arteries and some examples
contain substantial amounts of elastic fibres in the tunica media
e.g aorta and brachiocephalic trunk
What is the structure of medium muscular arteries and some examples
tunica media contains mostly smooth muscle fibres
e.g femoral, axillary and radial arteries
Where is the thoracic aorta located
anterior to the vertebral column, posterior to the heart, in the space at the end of the plura
What does the thoracic aorta branch into
Branches to supply the chest wall (intercostal arteries), oeasophogus and respiratory tree
What are paired and unpaired branches of arteries
Paired - arteries where two of them exist (left and right)
Unpaired - only one of its kind exist
What unpaired arteries branch off the abdominal aorta
Coeliac trunk
Superior mesenteric artery
Inferior mesenteric artery
What paired arteries branch off the abdominal aorta
Phrenic artery
Supradrenal arteries
Renal arteries
Ovarian arteries
Where are illiac arteries located
At the lower branching point of the abdominal arteries
What does the internal illiac artery supply blood too
Urinary bladder, rectum and some reproductive organs
What areas of the body does the external iliac artery supply blood too
lower extremities
What part of the body does the internal carotid artery supply
Eye and superior brain and head
What part of the body does the external carotid artery supply
Thyroid gland, neck and other structures in the head
What artery supplies the arm and hand
Subclavian artery
What are anastomoses and three examples of these in the body
these are connections between two blood vessels
e.g Circle of Willis, superficial palmer arch, mesenteric arches
What does the brachiocephalic trunk supply blood too
right arm and right side of head
(via branching into the right subclavian artery and right common carotid artery)
What blood vessel contains fenestrations
Capillaries
What is the structure of large veins and some examples
contain smooth muscle in the tunica media but the thickest layers the tunica externa
e.g superior vena cava, inferior vena cava, portal vein
What is the structure of small and medium veins and some examples
contains small amounts of smooth muscle, and the thickest layer is the tunica externa
e.g superficial veins in upper and lower limbs
What is the thinnest layer in veins
Tunica media
Where are deep veins usually found in the body
Alongside arteries
Where is blood coming from that is draining into the superior vena cava
head, neck, upper extermities and chest
Where is the blood coming from that is draining into the inferior vena cava
regions below the diaphragm
What are venous sinuses
large channel that drains deoxygenated blood
What makes the hepatic portal system different from all others in the body
Unlike in the rest of the body where all blood leading capillary beds goes straight back to the heart, blood coming out of the hepatic portal system goes through a second organ before going back to the heart
What is absent in terminal lymphatics that allow for the facilitation of movement of large proteins into the circulatory system
Doesnt contain tight junctions
What % of blood is plasma and RBC respectively
Plasma - 55%
RBC - 45%
What is atherosclerosis stroke
atherosclerosis plaque build up and artery blockage
What is hemorrhage stroke
Rupture of the vessel and haemorrhage
What is ischemic stroke
atherosclerotic plaque rupture and thrombus formation
What is the definition of vascular compliance
The total quantity of blood that can be stored in a given portion of the circulation for each mmHg pressure rise
What is the equation for vascular compliance
Compliance = volume/pressure
What vessels have the greatest compliance and how does this look on a pressure/volume curve
Veins have largest compliance, this means that their pressure/volume curve is much flatter because a change in volume doesnt affect the pressure too drastically
What neural activation is venous return aided by
Sympathetic innervation to stimulate smooth muscle contraction of venous walls
What are the relative pressures in the thoracic and abdominal cavities and how does this affect blood flow
Pressure in the thoracic cavity is lower than than of the abdominal cavity - this forces flood to move towards the heart while travelling in veins
What is the primary site of gas and nutrient exchange in the circulatory system
Capillaries
Role of precapillary sphincters
Control blood flow into the capillary bed, regulating tissue perfusion based on metabolic needs
What is net filtration and when this is positive what direction is fluid moving capillaries
Net filtration, when positive, is when blood i filtered out of the capillary bed and into the tissues
What are the two pressures involved in moving nutrients out of a capillary
Capillary pressure and Interstitial fluid colloid osmotic pressure
What are the two pressures involved in moving nutrients into a capillary
Plasma colloid osmotic pressure and interstital fluid pressure
What type of capillary pressures are responsible for the movement of water
colloid osmotic pressures
What type of veins have the lowest pressure
Large veins
What is the relative cross sectional area of arteries, veins and capillaries
Arteries have the smallest cross sectional area
Veins have a large cross sectional area
Capillaries have the largest cross sectional area
How does the elastic nature of arteries help maintain continuous flow
Elastin enable arteries to stretch and store some of the ejected blood during systole. During diastole, the elastic recoil of the artery wall helps push blood forward, smoothing out the pulsatile flow and maintaining a more continuous, stable flow.
What percentage of blood is pumped out the the aorta during diastole
40%
What type of flow is blood when it leaves the heart and when it reaches tissues respectfully
When it leaves the heart it is pulsatile flow
By the time it gets to tissues it is continuous flow
Is MAP increases, what occurs to the signals feeding back to the brain and what is the result of this
These increase - activating parasympathetic nervous system which will slow heart rate and inhibit sympathetic tone of veslles (allowing vasodialtion)
What is orthostatic hypotension
Occurs when someone goes from lying down to standing up very quickly.
Gravity pulls blood down to the legs, decreasing venous return and decreasing BP
What is the bainbridge reflex
This is the response to stretch in the left atrium. When baroreceptors detect stretch in the left atrium they
1. inhibit antidiuretic hormone
2. increase ANP
(reduce BP by excreting large amounts of urine)
What is detecting blood flow in the kidneys
Juxtaglomerular Apparatus
What is the effect of aldosterone
Salt and water retention by kidneys to increase blood volume
What is the equation for blood flow
Flow = pressure/resistance
What is the unit of blood flow
ml/min
In what part of the blood vessel is blood flow the highest and why
In the middle of the vessel because there is least resistance and drag
What is the equation for vessel conductance
conductance = 1/resistance
What does Poiseuille’s Law describe
The main take away from Poiseulles law is that flow is directly proportional to the 4 th power of radius.
(if radius increase, flow increases a lot)
What vessels provides the most resistance to blood flow
Arterioles
What is autoregulation of blood pressure
Process by which blood vessels adjust their diameter to maintain a stead blood flow to tissues, regardless of changes in systemic blood pressure
What mediates autoregulation
Myogenic responses - smooth muscle in the vessel wall contracts or relaxes in response to pressure changes
What is the primary goal of autoregulation
Ensure that tissues receive a constant supply of oxygen and nutrients, especially during fluctuations in bloop pressure or changes in metabolic demand
What is the change in shear stress on endothelium during exercise
Shear stress increases due to an increase in blood flow to exercising tissues
What is the effect of reducing intracellular Ca2+ on vessel tone
Decreasing intracellular Ca2+ decreases the contraction force of smooth muscles, leading to relaxation
What is the effect of cGMP on Ca2+ levels in smooth muscle cells
cGMP lowers Ca2+ levels within smooth muscle cells
What is the effect of norepinephrine on vessels
Vasoconstriction
Effect of histamine on vessels
Vasodilation
What is the primary mechanism in long term blood flow regulation in tissues
Angiogenesis
What is the baseline neural activity on vasomotor tone
SNS is always slightly active at rest, causing continuous partial constriction of blood vessels
What nervous system does the vasomotor centre primarily regulate
Sympathetic
What is aneurysm
Abnormal bulge or ballooning in the wall of a blood vessel
Where is atherosclerosis mainly found
elastic and muscular vessels
What vessels does hypertension effect the most
Small muscular arteries and arterioles
What is fibromuscular dysplasia
Congenital
Irregular thickening of medium and large muscular arteries resulting in stenosis
What is anomalous coronary artery origin
Congenital
When both coronary arteries arise over the same coronary cusp of the aortic valve
What areas of a blood vessels are at highest risk of developing plaques
ostia, branch points and areas where the flow patterns are disturbed and non-laminar
How does laminar non-turbulent flow contribute decreasing to atherosclerosis
Increases the production of transciption factors that turn on atheroprotective genes and turn off inflammatory gene trasncription
How does turbulant, non-laminar flow contribute to athlerosclerosis
Drives gene transcription that makes those sites atheroprone
What are the 2 dominent lipids in atheromatous plaques
cholesterol and cholesterol esters
How does hypercholesterolemia directly impair endothelial cell function
Increases ROS production. Causes membrane and mitrochondiral damage and oxygen free radicals to accelerate NO decay
How do foam cells contribute to atherosclerosis development
Secrete growth factors, cytokines and chemokines that create a vicious inflammatory cycle of monocyte recruitment and activation
What is inflammation triggered by in vessels
Accumulation of cholesterol crystals and free fatty acids in macrophages
What is normal blood pressure for people over 80 and diabetics, respectfully
Over 80s - 150/90
Diabetes - 140/90
What is the cause of essential (primary) hypertension
Genetics, environment and ageing
What is hyaline arteriolosclerosis and what pathology is it associated with
Arterioles have homogonous, pink hyaline thickening and luminal narrowing.
Plasma proteins leak across the injured epithelial and increase SMC matric synthesis
Caused by hemodynamic pressure of hypertension
What is hyperplastic arteriolosclerosis and what pathology is it asssociated with
In severe hypertension, vessels exhibit concentric, laminated thickening of walls with luminal narrowing.
SMC thickened, reduplicated basement membrane
What is arteriosclerosis
hardening of the arteries
What is monckberg medial sclerosis
Calcifications on the medial walls of the muscular arteries. Don’t encroach on the lumen so not usually clinically significant
What is fibromuscular intimal hyperplasia
Arteriosclerosis occurring in muscular arteries driven by inflammation
Atherosclerosis is the most common cause of what pathology
Peripheral artery disease
What is the first layer of vessels to thicken in plaque formation
intima media
What are some symptoms of peripheral artery disease
muscle pain that occurs with activity and stops with rest. Dull achy pain, muscle spasm, cramp, numbness
What are the different Fontaine stages of lower extremity arterial disease (I, IIa, IIb, III, IV)
I: asymptomatic
IIa: mild claudication (leg pain during exercise)
IIb: moderate to severe claudication
III: ischemic rest pain
IV: oilers and gangrene
What is the most common regions ofr peripheral artery disease
femoral popliteal segment
What are symptoms of superficial femoral artery disease
pain on exertion, pain at rest, non-healing ulcers from thigh to foot
What is superficial femoral artery disease mainly caused by
atherosclerosis in larger extermities
What will the blood flow sound like in someone with PAD
It will be audible due to the turbulant flow
What is the ankle brachial index
Measures the blood pressure in the ankle and divides it by the blood pressure in the arm
What ABI is indicative of PAD
<0.9
What tends to occur to the ABI during exercise
It decreases
What ABI is indicative of no artery blockage
1 - 1.4
What does a ABI >1.4 possibly indicate
possible calcification/vessel hardening
How would you calculate the right ABI
highest pressure in right foot/highest pressure in both arms
What ultrasound is used to image carotid artieres
B mode
What is Raynaud phenomenom
Exaggerated vasocontraction of arteries and arterioles in response to cold or emotion
Primary Raynaud’s
- Who does it primarily effect
- How does it effect the extremities
Effects young woman
Symmetrically affect extremities with no changes to arterial walls
Secondary Raynauds
- What causes it
- What is the effect on the extremities
Vascular insufficiency due to arterial disease
Asymmetric involvement of the extremities and progressively worsens
What are the characteristics of varicose veins
Abnormally dilated veins, torturous veins, vessel dilation, incompetence of valves
What veins are commonly involved in varicose veins
Superficial veins of the upper and lower leg
Are embolisms in superficial veins common
No
What causes portal vein hypertension and what does it lead to
Liver cirrhosis leading to opening of the portosystemic shunts
What is the consequence of the portosystemic shunts opening
increase in blood flow to the veins of the gastroesophageal junction, rectum and paraumbilical veins
What veins are mostly invovled in venous thrombosis
Superficial or deep veins of the lower expermities
What type of thrombi are usually found in veins and why
Red thrombi - due to the slow venous circulation, the blood tends to contain more enmeshed red cells and therefore known as red thrombi
What is the largest risk with DVT
Thrombi embolising to the lung and causing pulmonary infarctions
Inadequate hemostasis in blood vessels can lead to what
Haemorrhage
What is oedema
Accumulation of fluid in the tissues (usually feet/ankles/legs)
Any excess fluid in the vessels drains into what system and ends up where
Any excess fluid in the vessels drains into lymphatic vessels and returns into the vascular system via the thoracic duct
What is effusions
Accumulations of fluid in the body cavities
What does inflammation related oedema consist of
Protein rich exudates (mass of cells and fluid that has seeped out of blood vessels)
What does non-inflammatory oedema consist of
Protein poor transudates (thin watery liquid with little proteins and cells)
Transudates are common in what 4 diseases
Heart failure, liver failure, renal disease and malnutrition
What is the difference between IBS and IBD
IBS is a functional disorder (disease usually cant be seen in diagnostic procedures)
IBD is inflammation mediated and can be seen during diagnostics
What are 3 causes of oedema and effusions
Increased hydrostatic pressure
Reduced plasma oncotic pressure
Na+ and H20 retention
What is hyperaemia and its main symptom
High volumes of blood in the tissues due to arterial dilation
Causes erythema due to increased blood flow to that region
What is erythema
Redness of skin
What are congestions and what are they caused by
Increased blood flow to tissues caused by decreased outward flow from tissues
What is a major symptom of congestions
Cyanosis (abnormal blue/red colour due to accumulating deoxygenated blood)
Is congestion of blood vessels an active or passive process
Passive
What three factors cause thrombosis
Endothelial injury resulting in inflammation
Stasis/turbulent blood flow
Hypercoagulability
At what sites do arterial and cardiac thrombi usually occur at
Sites of turbulance or endothelial injury
At what sites do venous thrombi tend to occur at
sites of stasis
What direction do thrombi grow in, in both arteries and veins respectfully
Arterial thrombi grow in the retrograde direction of blood flow
Venous thrombi grow in the direction of blood flow
(this means that both are growing towards the heart)
Thrombi vs embolism
Thrombi is when a blood clots or forms an obstruction of the vessels
Embolism is when this clot moves through blood vessels and risks lodging somewhere else
What part of a thrombus is most at risk of embolism and why
The propagating portion of a thrombus is poorly attached and prone to fragmentation and embolism
What are mural thrombi
Thrombosis occurring in the heart chambers or in the aortic lumen
What 2 things underly aortic thrombi
Ulcerated atherosclerotic plaques and aneurysmal dilation
Where are the 3 most common sites of arterial thrombi
Coronary, cerebral and femoral arteries
What veins are frequency involved in venous thrombi
Those of the lower extremities
What are vegetations
Thrombi on heart valves
When does infected and sterile vegetations occur, respectfully
Infected thrombi occur due to bacteria, fungi, endothelial injury of the heart valves
Sterile vegetations can develop on noninfected valves in persons with hypercoagulable states
What is the first things that will occur to a thrombus once fully formed
It will begin propagation, accumulating additional platelets and fibrin
Once a thrombi embolises, what determines if it will undergo lysis or not
Recent thrombi are able to shrink and disappear
Older thrombi with extensive fibrin deposition and cross-linking are more resistant to lysis
When is the most useful time to administer therapeutic fibrolytic agents after a thrombotic event
Only effective in the first couple hours of the thrombotic event
If older thrombi are unable to be broken down by fibrolysis, what occurs to them
They become more organised (develop vasculature, smooth muscles and fibroblasts)
How can an MI predispose to a mural thrombi
An MI causes dyskinetic myocardial contraction and endocardial injury - trigger points for thrombi formation
What atrial abnormalities caused by rheumatic heart disease can cause atrial mural thrombi
Atrial dilation and fibirllation
What tissues are mostly effected by emoblism
Those with high blood supply - brain, kidney, spleen
What is the most common form of thromboembolism disease
Pulmonary embolism
What does pulmonary embolism usually orignate from
DVT
What is a paridoxial embolism
When a venous embolism passes through an interatrial and interventricular defect, into the systemic circulation
What is cor pulmonale
Right heart failure
What are two long term effects of pulmonary emboli
Pulmonary hypertension and right ventricular failure
Where so most systemic thromboembolisms arise from
Intracardiac mural thrombi which are usually associated with left ventricular wall infarcts
In response to what injuries are fat embolisms common
Skeletal injuries - injuries rupture vascular sinusoids in the marrow allowing for marrow or adipose tissue to herniate into the vascular space
How much air needs to be introduced into the body for it to be clinically relevant
100mls
What is the consequence of having air in the pulmonary capillaries
This can induce an intense inflammatory response with release of cytokines that may injure the alveoli
What is decompression sickness
When air is breathed at high pressures (e.g scuba diving) more gases are dissolved into the blood and tissues.
If the diver ascends (depresurises) too quickly, the nitrogen gas will come out of solution in the blood and tissues
What is The Bends
Rapid formation of gas bubbles in skeletal muscle and joints
What is The Chokes
Gas bubbles in vasculature of the lungs that cause oedema or collapse of the lung
What is treatment for decompression sickness
O2 chamber that forces gas bubbles back into solution
What is the primary situation when amniotic fluid embolism would occur
Labour/postpartum
What is the most common outcome of amniotic fluid embolism
Neurological defects
What is amniotic fluid embolism caused by
Infusion of amniotic fluid or foetal tissue into the maternal circulation via a teat in the placental membrane or rupture of uterine vein
What embolisms underly majority of infarctions
Arterial
Where are infarcts due to venous embolism more common
Common in organs with a single efferent vein (i.e testis and ovary).
What 2 occasions do white infarcts occur
With arterial occlusions in solid organs (heart, spleen, kidney)
Where tissue density limits the seepage of blood from adjoining capillary beds into the necrotic area
Repair responses usually replace infarcts with what, with the exception of what organ
Scar tissue, except in the brain where a CNS infarction results in liquefactive necrosis
When do septic infarctions occur and what do they turn into
Septic infarctions occur when infected cardiac valves vegetations embolise or when microbes seep into necrotic tissue
These infarcts turn into an absess
What are the 4 variables that will influence the outcome of vascular occlusion
Anatomy of the vascular supply
Rate of occlusion
Tissue vulnerability to hypoxia
Hypoxemia
What is cell shock
State of circulatory failure that impairs tissue perfusion and leads to cellular hypoxia
What is cardiogenic shock
Low cardiac output due to myocardial pump failure
What is hypovolemic shock
low cardiac output due to low blood volumes, such can occur with massive haemorrhage or fluid loss
What is SIRS
septic like conditions associated with systemic inflammation. May be triggered by non-microbial insults (burns, trauma)
What is sepsis
Life threatening organ dysfunction caused by a dysregulation host response to infection
What is aneurysm
Localised abnormal dilation of blood vessels or the heart
What is a true aneyrysm
Involves all the layers of an intact arterial wall of
What is a false aneurysm
defect in the capsular wall leading to extravascular hematoma connected to the intravascular space
What is an arterial dissection
tear along the inside of an artery
What are the two most important causes of aortic aneurysm
Atherosclerosis and hypertension
What are some risk factors to aneurysm
When the structure or function of the connective tissue within the vascular wall is compromised
Defects in synthesis or breakdown of connective tissue
Smoking, age, trauma
What is the most common cause of abdominal aortic aneurysm
Atherosclerosis in the abdominal aorta and common iliac arteries
Where are AAA’s usually located
Between the renal arteries and the bifurcation of the aorta
The risk of rupture of an AAA is directly related to what
The size of the aneurysm
What are thoracic aortic aneurysms common associated with
Hypertension and inflammation syndromes
What is Marfan syndrome
congenital disorder that affects the connective tissues (including blood vessels), predisposing individuals to aortic aneurysms and dissections
When can aortic dissections be fatal
Is they rupture through the adventitial and haemorrhage into the thoracic and abdominal cavities
What patients does aortic dissections usually affect
men 50+ with hypertension or younger patients with disease affecting the aorta
What does it mean if an aortic dissection is iatrogenic
It occurs following arterial cannulation during diagnostic catheterization or CABG
Aortic dissections are uncommon in substantial atherosclerosis - why?
The fibrosis is so thick that propagation of a dissection isnt really possible
What is a double barred aorta
An aortic arch subdivided into superior and inferior parallel channels, completely separated from each other by two separate adventitial layers.
What sections of the aorta does type 1 aortic dissection involve
Proximal lesions involved in either both the ascending and descending aorta (DeBakey type 1) or the ascending aorta only (DeBakey type II)
What part of the aorta does type B aortic dissections involve
Distal lesions involving the ascending aorta and usually beginning distal to the subclavian artery (DeBakery type III)
What is the most common and dangerous aortic dissection type
Type A
What is vasculitis and its symptoms
Inflammation of vessel wall
Fever, myalgia (muscle aches), arthralgias (pain in joint)
What vessels are commonly effected by vasculitis
Small vessels
What histological changes are seen in vessels with non-infection vasculitis
Vessels develop intimal thickening, reducing the luminal diameter
What are some examples of non-infection vasculitis
Giant cell arteritis, takayasu arteries, polyarteritis nodosa
What two bacteria species are particually common in arteritis
Aspergillus and Mucor
Example of infection vasulitis
Meningitis
Epidural and subdural haemorrhages generally occur due to what
Trauma
Subarachnoid haemorrhages almost always accompanies what
Parenchymal trauma
What is a hematoma
A pool of mostly clotted blood that forms in an organ, tissue, or body space
What is a epidural hematoma
Occurs when blood leaks into periosteum space, compressing the underlying brain
What is a subdermal hematoma
This occurs when blood seeps through the two layers of the dural
What is cerebrovascular disease
Injury caused by altered blood flow to the brain
What is a stroke
Neurological signs and symptoms that can be explained by a vascular mechanism
Difference between a stroke and transient ischemic event
A stroke must last for longer then 24 hours
What two mechanisms is stroke mostly cause by
Heamorrhage and ischemia
What sort of respiration does the brain only use
Aerobic
What is focal cerebral ischemia
Reduction or cessation of blood flow to a localised area of brain due to partial or complete arterial obstruction
The extent of tissue damage in cerebrovascular ischemia is dependant on what two things
Pressure of collateral circulation and duration of ischemia
The precise atomic site and size of an cerebral vascular ischemic lesion is determined by what
The magnitude and rapidity or the reduction of blood flow
What parts of the brain have little collateral flow
Deep penetrating vessels of the thalamus, basal ganglia and deep white matter
What region of the brain is most affected by embolic infarction
The region of the brain supplied by the middle cerebral artery
Where to emboli tend to lodge themselves in the brain
Pre-exsisting sites of luminal stenosis
What is a shower embolism
Fat embolism that has occurred after fractures
Focal cerebral ischemia caused by thrombotic occlusion is most commonly caused by what
Acute changes of vulnerable atherosclerosis plaques
What vasculitis may involve inflammation cerebral vessels, and thus be a cause of ischemic cerebral disease
Polyarteritis nodosa and other non-infections vasculatides
What is primary physical characteristic of brain infarcts at the beginning of their development
They are usually non-democratic (pale/anaemic) due to the limited collateral blood supply in the brain.
How can secondary haemorrhage occur in the brain
Due to ischemia-reperfusion injury due to embolism of fragmentation of a thrombi
What changes in appearance occurs to brain ischemic infarcts at these following time points:
6 hours
48 hours
2-10 days
10days - 3 weeks
6 hours - little change in appearance
48 hours - tissue becomes soft, pale and swollen
2-10 days - brain becomes gelatinous and friable
10 days - 3 weeks - tissue liquidises, leaving fluid filled cavity (oedma)
what is the difference in timeline of development between an ischemic and non-ischemic brain infarct
Ischemic infarctions will have blood extraversion (leaking) and reabsorption
Venous cerebral infarcts are usually haemorrhagic, true or false
True
What is a lacunar infarct
Infarcts that occur in deep brain structures such as thalamus, basal ganglia and white matter
What disease primarily causes lacunar infarcts
Arteriosclerosis (small vessel disease) causes small infarcts (lacunar infacts)
What is global cerebral hypoxia caused by
Reduction in cerebral perfusion (cardiac arrest, shock, severe hypotension) or decreased oxygen carrying capacity (CO poisening)
What are the two most sensitive cells to cerebral hypoxia
Neurons and glial cells
Where do boarder zone (‘watershed’) infarcts occur
In regions of the brain or spinal cord that lie at the most distal regions of the arterial blood supply
Border zone between the anterior and the middle cerebral artery distributions is at greatest risk
Where in the brain can intercranial haemorrhage occur
Either inside or outside the brain
What is intracranial haemorrhage in the epidural and subdural space caused by
Trauma
What is haemorrhage in the brains parenchymal and subarachnoid spaces mainly caused by
Cerebrovascular disease
What is intraparenchymal haemorrhage
Rupture of a small intraparenchymal vessel can result in primary haemorrhage within the brain, often associated with sudden onset of neurological symptoms
What accelerates atherosclerosis in larger and smaller arteries, respectfully
Larger arteries - hypertension
Smaller arteries - hyaline arteriolosclerosis
Thin arterial walls are more vulnerable to rupture in cerebral space, true or false
False - thickened arteriolar walls are more at risk of rupture
What risk factor is most commonly associated with lobar haemorrhages
Cerebral amyloid angiopathy (CAA) - peptides deposited in the walls of medium and small vessels making them very rigid
What is the most common cause of spontaneous subarachnoid haemorrhage
Rupture of saccular aneurysms in a cerebral artery
Where are majority of saccular aneurysms found
Near major arterial branch points in the anterior circulation
What patients are most likley to have a ruptured saccular aneurysm
Woman and people 50+
What is arteriovenous malformations
Tangled network of vascular channels
What are cavernous malformations
Distended, loosely organised channels arranged back to back with collagenised walls
Where does vascular malformations and cavernous malformations generally occur in the brain
Cerebellum, pons and subcortical regions
What is capillary telangiectasias
Small areas of dilated capillaries in otherwise normal brain tissues. Commonly found in pons
What is the most common site for arteriovenous malformations and what patients are most at risk of having one
Middle cerebral artery, particularly its posterior branches
Males are most at risk
What are 4 causes of vasular dementia
- Extended periods of time with infarcts
- Cerebral atherosclerosis
- Vessel thrombosis or embolism from carotid vessels or the heart
- Vertebral atherosclerosis from hypertension
What underpins the long term effects of diabetes
Persistent hyperglycaemia results in glucotoxicity.
This generates AGE (advanced glycation end products) which binds to inflammatory receptors on vascular membranes
What is diabetic macrovascular disease and hallmark symptom of it
Persistent hyperglycemia and insulin resistant results in endothelial dysfunction
Associated with accelerated atherosclerosis in the aorta and large and medium sized arteries
What is the most common cause of death in diabetics
MI caused by atherosclerosis of the coronary arteries
What is one main diabetic microangiopathies
Consistent morphological features of diabetes is diffuse thickening of the basement membranes
What changes occur to the permiability of capillaries in diabetic patients
Their capillaries are more leaky to plasma proteins
How many years after the onset of hyperglycemia does diabetic vascular disease make clincal signficance
15-25 years
What cerebral damage can occur due to diabetes
Glucotoxicity damages the endothelium induced chronic inflammation and promotes atherosclerosis
Why is ABI not always a useful diagnostic tool for measuring PAD in diabetic patients
Diabetic patients will sometimes have heavily calcified semi-compressible and incompressible tibial arteries
upon cessation of exercise during ABI test, what is an immediate indicator of a positive test for PAD
A 20% drop in ABI from baseline
What pedal pressure in diabetic and non-diabetic patients is indicative of healing
Diabetic - >100mmHg
Non-diabetic - >60mmHg
What types of tumors are primary tumours of large vessels
Sarcomas
What is telangiectasia and is this a true neoplasm
Permanent dilation of pre-existing small vessels that forms a discrete red lesion
This is not a true neoplasm
What is a neoplasm
An abnormal mass of tissue that forms when cells grow and divide more than they should or do not die when they should
What is the most common form of ectasias
Nevus flammeus (birthmark) - composed of dilated vessels, mostly spontaneous.
What are spider telangiectasias and where do they most occur
Non neoplastic vascular malformations commonly occur on face, neck and upper chest
What is Hereditary hemorrhagic telangiectasia
Autosomal dominant disorder that are malformations composed for dilated capillaries and veins that are present in birth
What are Haemangiomas
Common benign tumours in infancy and childhood
What are Cavernous haemangiomas
These are tumours composed of large, dilated vascular channels. Little clinical significant
What are the most common Haemangiomas
Capillary Haemangiomas - composed of thin-walled capillaries with scant stroma
Kaposi sarcoma, haemangioendotheliomas and angiosarcomas are all what
Malignant tumours
What is Kaposi sarcoma caused by
Herpes Virus 8 - most common in AIDS patients
What are the most common sites for angiosarcomas
Skin, soft tissue, breast, liver
What in contrast referring too in ultrasound
The amount of colour or greyscale differentiation that exists between different image features
What is resolution in regards to ultrasound
the ability for the US probe to demonstrate differentiation between tissues having different characteristics
What is axial resolution in US
The ability to display small targets along the path of the beam as separate entities (also referred too as longitudinal axis)
What is axial resolution in US dependant on
The spatial pulse length (number of cycles in a given US pulse)
How can spatial pulse length in US be enhanced
Increasing frequency emitted by the probe - the shorted SPL will improve the axial resolution but will no penetrate tissue
What is lateral resolution in US
The ability to distinguish between two separate targets perpendicular to the beam path
What is lateral resolution in US dependant on
The width of the US beam
In order for the lateral resolution in US to be high, the near field needs to be _____
Low
What is the equation for near field lenght
Near field legnth = diamiter^2 / 4λ
The near field length in US increases with what changes in wavelength, frequency and aperture
Shorter wavelength
Higher frequency
Larger aperture
What does focusing the US probe do to the narrowest region of the beam
Shortens it
What is the focal legnth in regards to US
The length between the region and the tranducer
How is high later resolution achieved on US in regards to wavelength, focal length and aperture
Short wavelength
Short focal length
Wide aperture
What is temporal resolution in US
The time from the beginning of one frame to the next
Represents the ability for the US system to distinguish between instantaneous events of rapidly moving structures
How can frame rate be enhanced in US
Reduced depth of penetration
Reduced number of focal points
Reduced scan lines
What is temporal resolution dependant on in US
Frame rate
In regards to power, what is the ideal amount of power used in US
We want this to be at the minimum for the required depth penetration. Too much power will result in high exposure
What is intensity in relation to US
The power flowing through unit area presenting at 90 degrees to the direction of propogation
What 4 factors contribute to attenuation of US wave
Reflection
Refraction
Absorption
Scattering
What is acoustic impedance in US
The resistance which represents US wave penetrating the tissue
When does reflection occur in US
Occurs when the interface between two mediums is large relative to the wavelength
What is the difference between specular and diffuse reflections in US
Specular reflection is when a US wave hits a smooth, large surface (like bone) and the sound wave is reflected back in a singular uniform direction
Diffuse is when an US wave hits an irregular surface the reflection return to the transducer in a chaotic and disorganised pattern
What does diffuse reflection look like on an US display
Various shades of grey located within scructures
What is refraction
Deviation in the path of a beam when the angle of incidence to an interface is no 90 degrees
Propogation velocities influence the direction of refraction, true or false
True
What is the critical angle in regards to US and what does it cause
The largest possible angle of incidence which results in a refracted beam
Results in the refracted beam travelling along the boundary between two media
What happens is the incidence angle is greater then the critical angle in US
The sound waves will be completely reflected by the boundary, a phenomenon known as total internal reflection
What is absorbtion in relation to US
The conversion of the sound waves mechanical energy into heat energy within the tissue
What is the primary mechanism for which attenuation of US occurs
Absorption
As frequency of the US wave increases, what occurs to the amount of absorption
Increases
Where does scattering occur in US
At the interface within the sound beam path
What information does scattering tell us about in an US display
Scattering provides most of the textural information present in the images
What 3 things is scattering in US dependant on
Frequency
Angle of approach
Interface being much smaller then the wavelength
For scatter to occur in US, what must the relationship be between the interface and wavelength
They must be the same in order for scattering to occur
If you have to little gain, what is the resulting issue in the image
The structures in the image are not well defined
If you have too much gain what will be the resulting issue in the image
It will be oversaturated, creating a snowstorm effect
What part of an US echo does gain amplify
Gain only amplifies the returning echos
What is time gain compensation in US
The deeper the returning wave, the less energy it will have. The gain automatically increases these signals more to compensate for the additional attenuation these waves go through to get back to the surface
What is frame rate
Number of images generated per second, expressed as frames per second and contributes to the ‘smoothness’ of the motion capture
What is the result of increasing frame rate averaging
Can enhance subtle textural differences.
Decreasing or removing frame averaging in US is reccomended when
Scanning highly mobile tissues
What is frame averaging in US
This allows the accumulation of echo over two or more frames
What will happen is the pulse repetition frequency is too low
Aliasing will occur
What will happen is the pulse repetition frequency is too high
It will detect slower moving blood, the scale of spectral display will not be fully utilised
What does the pulse repetition frequency need to be in US to avoid aliasing
PRF needs to be twice the maximum Doppler frequency
When working with colour box doppler, what is important when positioning the box on screen
The box should be at the same angle as the transducer probe
What is the effect of variation and contrast when increasing and decreasing dynamic range in US
Decreasing dynamic range = limited variation, increased contrast
Increasing dynamic range = limited variation, increased contrast
What resolution is usually used first when doing US
Begin with axial resolution then move to longitudinal
What are 5 ways we can reduce artefact in US
Turn down gain
Alter angle of probe
Scan in two planes
Have patient use different breathing technique
Change tranducer frequency
What are 5 ways you can optimise the image in B mode US
- Set the focal zones of interest on the scan image
- B mode frame rates should be high
- Zooming in on screen
- Relatively high contrast
- Ensure returning echo’s are uniform by adjusting the total gain and depth gain
What are 3 ways we can optimse the image in colour doppler US
- PFR should be high
- Tilt colour box in direction of blood flow
- Colour box should be as small as possible
What is the usual pulse repetition frequency of colour flow doppler in vascular US
3000-4000Hz
What are 3 ways you can optimise imaging in spectral US
- PRF should be set high
- High pass filter to remove wall thump
- Sample volume should be placed in the centre of the vessel or at the point of maximum velocity
What are 3 reasons to why a doppler signal may be showing above or below the baseline
Alising
Mirroring
Flow reversal
What 4 criteria must quality assurance techniques always meet
- Always provide an objective and quantifiable measure of performance
- Should be relevant clinical application
- Should be reproducible over time scale of years
- Should be sensitive enough to detect change in performance before it comes clincally relevent
Crystal dropout, sensitivity, uniformity and noise are all what type of quality assurance tests
Realtive paremeter tests
What is crystal dropout in US
When a piezoelectric crystal in an US probe is faulty, this will result in a vertical line of reduced echo signal
How can sensitivity be assessed in quality assurance
Examining the depth to which the reverberation pattern extends
How is uniformilty in US quality assurence tested
Using a US phantom, there should be no localised bright or dark spots is the tranducer is working properly
What are absolute performance tests used for
To compare with other machines that provide the same function
What is power doppler US and what does it measure
New type of colour doppler US used to show much smaller vessels and slower blood flow. Cant show direction of flow.
What type of doppler probe is used in vascular ultrasound
8Hz with narrow face
What three parameters does the ABI depend on
Data from the ABI
Wave morphology from doppler ultrasound
Sound interpretation
What vessel is the pressure taken from in the ankle in ABI testing
Dorsalis pedis
What is the ideal waveform in doppler US of ABI testing
Waveforms should be multiphasic (upstroke, downstroke, upstroke)
What changes have occurred to the structure of a vessel that would cause a reduction in waveform observed in doppler US
Shifts in waveform are lost due t the reduction in elasticity within the vessel
What waveforms are associated with severe artery disease
High monphasic or dampened monphasic
In which patients can ABI not be performed on
Patients with confirmed or suspected DVT or severe leg pain
What are two variations to ABI testing that can be considered
Segmental pressure index and toe brachial index
What value of toe brachial index is normal
> 0.7
What value of toe brachial index is severe
<0.35
What is carotid duplex ultrasound used for
Determine the presence and shape of atherosclerotic plaques in the carotid artery
What probe is required in carotid duplex US
Linear probe with intensity greater then 7Hz, depth focus 30-40nm, frame rate 25Hz, dynamic range 600dB
What are 4 symptoms of carotid artery blockage
Blurred vision
Confusion
Memory Loss
Weakness
What view of the carotid arteries would you get in a longitudinal view
You will see the length of the artery as if you were inside it
What view of the carotid arteries would you get in transvere US view
birds eye view, like you chopped someone head off and were looking down the arteries
When doing carotid duplex US, what order do you assess the vessels
First find the CAA on the left in transverse plane
Once identified, move the probe until you see the bifurcation, switch to longitudinal plane and observe the ECA and ICA
What is the main structural difference between the ICA and ECA in carotid duplex US
The ECA is larger and wider
What is the normal thickness of the intima-media layer of carotid arteries
0.5-0.9mm
Normal vessels should have a double laminar structure, true or false
True
What will you see in a carotid duplex US in early stages of carotid artery disease
Thickening of the intima-media layer, uneven surface
What should be the relative resistance, diastolic flow and velocity range be in the vertebral artery
Low resistance
High diastolic Flow
Velocity range 60-80ms
What is the difference between ICA and ECA in spectral doppler
ICA waveform is pulsatile at slower rates and have lower diastolic flow then ECA
If no flow is observed in spectral doppler what settings can you change
Altering the pulse repetition frequency or high pass filter
What is the pulsatility index in US
The difference between the peack systolic velocity and the end diastolic velocity
What is the resistance index in US
The pulsatile flow that results the resistance of blood flow
In a normal spectral carotid duplex US what are the relative resistance
ICA - Low resistance flow
ECA - High resistance flow
CCA - in between the two
What are characteristics of a normal carotid duplex US
High peaks, well defined, varience
What will change in the velocity of a carotid duplex with stenosis
Increase in velocity will be observed
In carotid duplex, in what terms is the severity of stenosis described
Described as a percentage, velocity is only considered when the diameter reduction is greater than 50%
What three methods can stenosis of the ICA be treated
- Carotid endarterectomy (plaque physically removed)
- Carotid-carotid bypass
- Stenting
As stenosis increases in the ICA, what occrs to the PSV and EDV
PSV decreases
EDV increases
What disease is indicated by pulsatile swelling of the neck
Carotid body tumour
What are 3 effects calcified atheroma can cause in carotid duplex
Shadowing artefact
Reduced quality of image
Gives false positive that flow is absent
How does vessel tortuosity effect carotid duplex outcoems
The vessels may not appear in a single plane, so doppler may need to be used in multiple angles
What is echogenicity in regards to plaque
The plaques ability to reflect echo (high echogenicity, more white it will be on echo)
What types of plaque are echolucent
type 1 and 2
What is transcranial doppler used to study
Intracranial structure and the vessels within (circle of willis)
What are the 2 main arteries of interest in transcranial doppler
Middle cerebral artery and internal carotid artery (located in the circle of willis)
What are four indications for transcranial doppler
Vasospasm, evaluation of left and right shunt, screening of paediatric paitents, sickle cell disease
In the transtemporal window of transcranial doppler, what are the 4 arteries of interest
middle cerebral artery, anterior cerebral artery, posterior cerebral artery and terminal ICA
In the transorbital window of transcranial doppler, what are the 2 vessels of interest
ophthalmic artery and carotid syphon
What transcranial doppler window can you use in neonates to see the circle of willis
Transtemporal window
What are 4 indications for AAA screening
Pulisile abdomen, back pain, abdominal pain, acute shock
What is the vessel of interest in AAA screening
Abdominal Aorta
In a normal ultrasound of an aorta, how wide should it be maximum
2.5cm
In pulse wave doppler, what types of waveforms should the proximal aorta and distal aorta have, respectfully
Proximal - biphasic
Distal - triphasic
What does an intimal flat tell us when imaged in a ultrasound of a vessel
Excess tissue showing there has been a tear in the vessel
What conditions can make AAA screening difficult to visualise
Bowel gas or obesity
What are 2 indications of assessment of lower limb disease
Pain/cramping in muscles when walking
Pain at rest
What are the 5 arteries of interest when doing an assessment of the lower limbs
Aortoiliac artery, CFA, femoral artery, popliteal arteries, tibial arteries
What waveform should we expect the lower limb arteries to have
Triphasic
What are the two most commonly upper limb arteries affected with atherosclerosis
Subclavian artery and axillary artery
Where are the 3 common areas of compression that are being assessed in a thoracic outlet syndrome assessment
Subclavian artery, artery that runs between the first rib and clavicle and subcoracoid region
What frequency is used for DVT study
5-8MHz
What are the 4 arteries of interest in the DVT study
Common femoral veins
Superficial veins
Popliteal Veins
Calf Veins
Do we want the PRF high or low in DVT studies
Low
What is the purpose of calf compression assessment during DVT study and what should the veins be like
To assess the competence of the valves, the flow in the veins towards the heart should be temporality increased or augmented
What are the two maneuvers done in DVT study
Calf compression and valsava maneurver
How do you perform calf compression manoeuvre
Place hand around the calf and give a firm queeze then quickly release
What should be the result of a calf compression manourver in healthy people
Flow augmentation should be sufficiently strong enough to produce a transient peak flow velocity of 30cm/s in the main superficial veins.
Valve closure should be rapid upon squeeze release
What is the Valsalva maneuver used to assess
The competence of the proximal deep vein and saphenofemeral
Explain how the Valsalva manoeuvre is done
Patient is told to deeply inhale an then push out and expand their cheeks without breathing out, while at the same time bearing pressure done the abdomen
What occurs to the pressure inside the body during the Valsalva manoeuvre
It increases the intraabdominal pressure (increasing venous blood pressure in the iliac and femoral veins)
If the veins are healthy, what should be seen in the valsava manouver
There should be no reflux present in the saphenofemoeral junction or proximal superficial femoral vein
What is varicose veins
Dialted tortous superficial venous channels that accompany the superficial veins of the upper and lower limbs
What is the difference in the action of the vein valves in normal and varicose veins
Normal veins - only the veins upward of the blood open (so unidirectional flow)
Varicose veins - all veins flow so blood flows in both directions
What nervous system is vascular smooth muscle regulated by
SNS
What is endothelin released by, what does it do and what is the result of its action
Released by endothelial cells
Causes vasocontraction
Stimulates release of various hormones (ANP, aldosterone, adrenaline)
Renin-aldosterone system activation causes the release of what 2 primary hormones
Renin and Aldosterone
What is a common side effect of vasoactive drugs
Reflex tachycardia
What is the direct and indirect mechanism of vasoconstrictor drugs
Direct - act directly onto smooth muscle
Indirect - act on endothelial cells or CNS cells
What are some types of drugs that target the nervous system to cause vasocontriction
Alpha1-adrenoreceptor agonists and drugs that release noradrenline
What are some direct vasodilators
L-type Ca2+ blockers and drugs that open up KATP channels
What are some examples of indirect vasodilator drugs
cGMP, beta-2 antagonists, ACE inhibitors
Why are SNS targeting vasodilator drugs not well tolerated
Because they target the whole SNS they have lots of side effects
what is the main unwanted side effect of antihypertensive drugs
Postural Hypotention
What drugs tend to be used to target PAD
Drugs that reduce the risk of ischemia and strokes - antiplatelet drugs
What are some drugs used for pulmonary hypertension
Anticoagulants, diuretics
What is the role of statins
Block synthesis of cholesterol within hepatocytes
What is the rate limiting enzyme in cholesterol synthesis
HMG-CoA
What is the mechanism of PCSK9 drugs
reduce the degradation of LDL receptors
What is one disadvantage to mechanical treatment of thrombi
Any mechanical process in the vessel will result in healing = intimal thickening.
What is interventional ultrasound
Using a catheter to deliver ultrasound waves to the trombi to break it up and remove the occlusion
In what situations do synthetic grafts and autologous grafts work better
High flow locations are better with synthetic graft
Small vessels are best with autologous grafts
