Week 2 CVS Flashcards
Define atherosclerosis
Formation of focal elevated leisons (in intima of large and medium sized arteries)
atheromas
In coronary arteries atheromatous plaques narrow lumen leading to ischaemia
Can have serious consequences due to myocardial ischaemia
Complicted by thromboembolism
Ateriosclerosis
- Not Atheromatous
- Smooth msucle hypertrophy, apparand reduplication of internal elastic laminae, intimal fibrosis decreases vessel diameter
- Contributes to high frequency of cardiac, cerebral, colonic and renal ischaemia in the elderly.
- Clinical effects most apparent when CVS further stressed by haemorrhage, minor sugery, infection or shock
What are the 4 different developmental stages of an atheroma?
Fatty Streak
Early atheromatous plaque
Fully developed atheromatous plaque
Complicated atheroma
Describe a fatty streak atheroma
- Earliest significant leisons
- Found in young children
- Yellow linear elevation of intimal lining
- Comprises masses of lipid-laden macrophages
- No clinical significance
- May disappear
Describe early atheromatous plaques
- Young adults onwards
- Smooth yellow patches in intima
- Lipid laden macrophages
- Progress to established plaques
Describe fully developed atheromatous plaques
- Central lipid core with fibrous tissue cap, covered by arterial endothelium
- Collagens (produced by smooth muscle cells) in cap provide structural strength
- Inflammatory cells (macrophages, T-Lymphocytes, mast cells) reside in fibrous cap: recruited from arterial endothelium
- Central lipid core rich in cellular lipids/debris derived from macrophages (died in plaque)
- Soft highly thrombogenic, often rim of ‘foamy’ macrophages [foamy due to uptake of oxidised lipoproteins via specialised membrane bound scavenger receptor]
- Dystrophic calcification extensive, occurs in late plaque development [marker for atherosclerosis in angiograms/CT]
- Forms at arterial branching points/bifurcations (turbulent flow)
- Late stage plaques: Confluent, cover large areas
Describe a complicated atheroma
- Features of established atheromatous plaque (lipid-rich core, fibrous cap) plus
- Haemorrhage into plaque (calcification)
- Plaque rupture/fissuring
- Thrombosis
What are the signs of major hyperlipidaemia
- Familial/primary vs acquired secondary
- Biochemical evidence: LDL, HDL, total cholesterol, triglycerides
- Premature corneal arcus
- Tendon xanthomata (knuckles, achilles)
- Xanthelasmata
Describe the development of atheromatous plaques
Two step process:
- Injury to endothelial lining of artery
- Chronic inflammation and healing response of vascular wall to agent causing injury
- Chronic/episodic exposure of arterial wall to these processes -> formation of atheromatous plaques
Describe the pathogenesis of atherosclerosis
- Endothelial injury and dysfunction
- Accumulation of lipoproteins (LDL) in vessel wall
- Monocyte adhesion to endothelium → migration into intima and transformation to foamy macrophages
- Platelet adhesion
- Factor release from activated platelets, macrophages → smooth muscle cell recruitment
- Smooth muscle cell proliferation, extracellular matrix production and T-cell recruitment
- Lipid accumulation (extracellular and in foamy macrophages)
What are the 2 most common causes of endothelial injury?
Haemodynamic disturbances (turbulent flow) Hypercholesterolaemia
Describe Describe how hypercholesterolaemia can cause injury to the endothelium
- Chronic hypercholesterolaemia can directly impair endothelial cell function by increasing local production of reactive oxygen species
- Lipoproteins aggregate in intima and are modified by free radicals produced by inflammatory cells → modified LDL accumulated by macrophages but not completely degraded → foamy macrophages → toxic to endothelial cells plus release of growth factors, cytokines
describe how endothelial cells are functionally altered in atherosclerosis
- enhanced expression of cell adhesion molecules (ICAM-1, E selectin)
- High permeability for LDL
- Increased thrombogenicity
- Inflammatory cells, lipids -> intimal layer -> plaques
Describe advanced plaque formation
- Large numbers macrophages, T-Lymphocytes
- Lipid-laden macrophages die through apoptosis -> Lipid into lipid core
- Response to injury = chronic inflammation process
What are the consequences of atheroma
Many plaques form over lifetime, many clinically unnoticed
Acute changes in plauqes (complicated atheroma) can have serious consequences
What does stenosis of 50-75% of vessel lumen lead to?
Critical reduction of blood flow in distal arterial bed -> reversible tissue ischaemia
What can very severe stenosis lead to?
Ischaemia - pain at rest
[unstable angina, eg ileal popliteal artery stenosis -> intermittent claudication]
What can longstanding tissue ischaemia lead to?
Atrophy of affected organ eg aterhosclerotic renal artery stenosis -> renal atrophy
What does rupture exposing collagen, lipid and debris to the blood stream do?
these are all highly thrombogenic plaque contents. Leads to the actiation of coagulation cascade and thrombotic occlusion in very short time
What does total occlusion of an artery lead to?
Irreversible iscahemia
embolisation of the distal arterial bed
- Detachment of small thrombus fragments from thrombosed atheromatous arteries -> embolise distal to ruptured plaque
- Embolic occlusion of small vessels -> small infarcts in organs
Ruptured atheromatous abdominal aortic aneurysm
- Media beneath atheromatous plaques gradually wakened (lipid-related infammatory activity in plaque)
- This leads to gradual dilation of vessle
- Slow but progessive, seen in elderly, often asymptomatic
- Sudden rupture -> massive retroperitoneal haemorrhage
What diameter does an aneurism become at risk of rupture?
5cm
What is a mural thrombuis
Emboli to legs
Describe vulnerable atheromatous plaques
- Thin fibrous caps, large lipid core, prominent inflammation
- Proncounced inflammatory activity -> degradation, weakening fo plaque -? increased risk of plaque rupture
- Secretion of proteolytic enzymes, cytokines and reactive oxygen species by plaque inflammatory cells
- Often large fibrocalcific component, little inflammation
What is blood flow?
Amount of blood moved per unit time
What is stasis?
Stagnation of blood flow
What is turbulence?
Forceful, unpredictable flow
What do defects in blood flow cause?
- Thromboembolism
- Atheroma
- Hyperviscosity
- Spasm
- External compression
- Vasculitis
- Vascular steal
What is virchows triad?
- Changes in the blood vessel wall
- Changges in the blood constituents
- changes in the pattern of blood flow
Describe the pathogenesis of thrombosis
- Atheromatous CA
- Turbulent blood flow
- Loss of intimal cells, denuded plaque
- Collagen exposed to which platelets adhere
- Fibrin meshwork forms - RBC’s trapped
- Alternating bands: Lines of Zahn
- Further turbulence and platelet deposition
- Propagation
- CONSEQUENCES
What do the consequences of thrombosis depend on?
Site
Extend
colalteral circ.
Common clinical scenariosL DVT, Ischaemia limb, MI
What is an embolus
Detached intravascular soil, liquid or gaseous mass
Where do venous thromboembolus originate from?
Originate from deep venous thromboses (lower limbs)
What is the most common thromboembolic disease
Venous thromboembolus
What are the types of embolus?
Fat Gas Air Tumour Trophoblast Septic material Amniotic fluid embolism Bone marrow Foreign bodies
What is rheumatic fever
- Disease of disordered immunity
Where are some inflammatory changes caused by rheumatic fever
- Heart
- Joints
- Sometimes neurological symptoms
What is the presentation of someone with RF
Typically present with ‘flitting’ (painful) polyarthritis of large joints (wrists, elbows, knees, ankles) plus skin rashes and fever
What may RF cause in the heart?
Pancarditis (inflammation affecting endocardium, myoicadium in acute phase; heart murmers common)
Describe how RF may cause damage to the heart tissue
May be combination of antibody mediated and T cell mediated reactions
What is an aschoff body
Focus of chronic inflammatory cells, necrosis and activated macrophages.
Seen in heart in acute rheumatic fever
What can pancarditis in acute RF progress to?
Chronic Rheumatic heart disease, mainly manifesting as valvular abnormalities
What does inflammation of the endocardium and left sided valves result in?
fibrinoid necrosis of the valve cusps/chordea tendineae over which (and long line of closure) form small vegitations
What is rheumatic heart disease characterised by?
Principally by deforming fibrotic valvular disease, particularly involving the mitral valve: Typically leaflet thickening commissural fusion and shortening and thickening and fusion of the chordae tendineae
What can RHD cause?
Mitral stenosis
Can cause mitral regurg but now most commonly due to ischaemic heart disease
Potentially still causes an aortic regurg/incompetance
What are the 4 types of hypoxia?
Hypoxic
Anaemic
Stagnant
Cytotoxic
What is anaemic hypoxia
Normal inspired O2 but blood abnormal
What is stagnant hypoxia?
Normal inspitred O2 but abnormal delivery
- Local: occlusion of vessel
- systemic: Shock
What is cytotoxic hypoxia?
Normal inspired O2 but abnormal at tissue level
What is the functional effect of ischaemia
Blood O2 supply fails to meet demand due to decreased supply; incrased demand or both
What are the 2 types of necrosis and where are they seen
Coagulative necrosis - eg heart, lung
Colliquitive necrosis - brain
Describe the appearance of an infarct after less than 24 hours
No change on visual inspection
A few hours to 12 hours post insult, able to see swollen mitochondria on electon microscopy
Describe the appearance of an infarct between 24 and 48 hours
Pale infarct seen in myocardium, spleen, kidney and solid tissue
Red infarct seen in the lung and liver
Microscopically: acute inflammation initially at edge of infarct; loss of specialised cell features
Describe the appearance of an infarct after approx 72 hours
Macroscopically:
pale infarct - yellow/white and red periphery
Red infarct - little change
Microscopically: Chronic inflammtion; macrophages remove debir, granulation tissue, fibrosis
What is the end result of an infarct?
Scar replaces area of tissue damage
Shape depends on territory of occluded vessel
Describe the presentation of MI 4-12 hours after the initial occlusion
Early coagulation necrosis, oedema, haemorrhage
Describe the presentation of MI 12-24 hours after the initial occlusion
Ongoing coagulation necrosis,
myocytes changes
Early neutrophilic infiltrate
Describe the presentation of MI 1-3 days after the initial occlusion
Coagulation necrosis
Loss of nuclei and striations
Brisk neutrophilic infiltrate
Describe the presentation of MI 7-10 days after the initial occlusion
Well developed phagocytosis
Granulation tissue at margins
Describe the presentation of MI 10-14 days after the initial occlusion
Well established granulation tissue with new blood vessels and collagen deposition
Describe the presentation of MI 2-8 weeks after the initial occlusion
Increased collagen deposition, decreased cellularity
Describe the presentation of MI >2 months after the initial occlusion
Dense collagenous scar
What is a transmural infarction?
When the ischaemic necrosis affects the full thickness of the myocardium
What is a subendocardial infarction?
When the ischaemic necrosis mostly limited to a zone of myocardium under the endocardial lining of the chart
Describe the histological features of a transmural and subendocardial infarction
Histological features are the same - granulation tissue stage followed by fibrosis - in subendocardial infarct possibly slightly shortened compared to transmural infarct
How are acute infarcts classified?
According to whether there is elevation of the ST segment on the ECG
What is the classification of a myocardial infarct If there is no ST segment elevation but a significantly elevated serum troponin level
Non STEMI or an NSTEMI
What do NSTEMIs tend to correlate with?
Subendocardial infarctions
What is angina
A discomfort in the chest and or adjacent area associated with myocardial ischaemia but without myocardial necrosis
What is the most common cause of angina?
Obstructive coronary atheroma
What features make an angina diagnosis less likely
Sharp/Stabbing pain; pleuritic or pericardial
Associated with body movements or respiration
Very localised: pinpoint site
Superficial with/or without tenderness
No pattern to pain, particularly if often occuring at rest
Begins some time AFTER exercise
Lasting for hours
Describe a 1 on the scale of severity of the Canadian classification of angina severity (CCS)
Ordinary physical acticity does not cause angina symptoms, only on significant exertion
Describe a 2 on the scale of severity of the Canadian classification of angina severity (CCS)
Slight limitation of ordinary activity, symptoms on walking 2 blocks or >1 flight of stairs
Describe a 3 on the scale of severity of the canadian classification of angina severity (CCS)
Marked limitation, symptoms on walking only 1-2 blocks or 1 flight of stairs
Describe a 4 on the scale of severity of the canadian classification of angina severity (CCS)
Symptoms on any activity, getting washed/dressed causes symptoms
Describe the possible presentation of angina
Obesity Xanthalasma and corneal arcus (hypercholesterolaemia) Hypertension Abdominal aortic aneurism Arterial bruits Abscent or reduced peripheral pulses Diabetic retinopathy Hypertesive retinopathy Fundoscopy
What are the signs of exacerbating or associated conditions
Pallor anaemia
Tachycardia: Tremor, hyper-reflexia of hyperthyroidism
Ejection systolic murmur of mitral regurg
Signs of HF such as basal crackles, elevated JVP, peripheral oedma
What are the investigations for angina
Bloods
CXR
ECG
ETT
What is a diagnostic test for angina
ETT