Vascular and Ischaemic Heart Disease Flashcards
Where do the right and left coronary arteries arise from?
The base of the aorta
Where does most coronary venous blood drain into?
The coronary sinus and then into the right atrium
What area of the heart becomes deprived of blood supply if the left coronary artery becomes blocked?
Left ventricle
Give four special adaptations of coronary circulation?
- High capillary density
- High basal blood flow
- High oxygen extraction (75% compared to 25%)
- Extra oxygen can only be supplied by increasing coronary blood flow
What does decreased PO2 do to the coronary arteries?
Causes vasodilatation
What is an intrinisc mechanism of coronary blood flow, and matches flow to demand?
Metabolic hyperaemia
What is a potent vasodilator for coronary blood flow (intrinsic mechanism)?
Adenosine from ATP
What type of nerves are coronary arterioles supplied by?
Sympathetic vasoconstrictor nerves
What are sympathetic vasoconstrictor nerves in coronary arterioles over-ridden by?
Metabolic hyperaemia as a result of increased heart rate and stroke volume
What does sympathetic stimulation of the heart result in?
Coronary vasodilatation despite direct vasoconstrictor effect
What substances activates beta-2-adrenoceptors, which causes vasodilatation?
Adrenaline
What receptors does sympathetic stimulation act on in relation to coronary blood flow?
Alpha receptors
What do increased metabolites such as K, PCO2 and H+ do to coronary blood flow?
Increase it
What does an increase in adenosine, do to coronary blood flow?
Increases it
When does peak left coronary flow occur?
During diastole
What does shortening diastole (e.g. very fast heart rate) do to coronary flow?
Decreases it
What gives blood supply to the brain?
Internal carotids and vertebral arteries
What is very sensitive to hypoxia in the brain?
Grey matter
What two arteries form the basilar?
Two vertebral arteries
What arteries anastomose to for the circle of Willis?
Basilar and carotid arteries
Where do the major cerebral arteries arise from?
The circle of Willis
What is caused by an interruption/cut-off of blood supply to a region of the brain?
Stroke
What are the two main types of stroke?
- Haemorrhagic bleeding
2. Ischaemic stroke
What type of stroke is described - blood leaks out of artery wall which is damaged?
Haemorrhagic stroke
What type of stroke is dewscribed - blood clot forms on atheroma on artery wall or comes from another part of body and gets stuck, blood cannot flow past?
Ischaemic stroke
What is autoregulation of cerebral blood flow guard against?
Changes in cerebral blood flow if mean arterial blood pressure changes within a range (60 - 160 mmHg)
In relation to autoregulation of cerebral blood flow: what happens to resistance vessels automatically when MABP rises?
Resistance vessels constrict to limit blood flow
When does autoregulation fail in relation to MABP falling?
Below 60mmHg
What does MABP below 50 mmHg, result in?
Confusion, fainting and brain damage if not quickly corrected
What does increased PCO2 do to cerebral vessels?
Causes cerebral vasodilatation
What does decreased PCO2 do to cerebral vessels?
Cause vasoconstriction (which is why hyperventilation could lead to fainting)
What is the term for blood flow increasing to active parts of the brain?
Regional hyperaemia
What is normal intracranial pressure (ICP) within the skull?
8 - 13 mmHg
What is the equation for cerebral perfusion pressure (CPP)?
CCP = MAP - ICP
What two things could increase ICP?
- Head injury
2. Brain tumour
What does increasing ICP, do to CPP and cerebral blood flow?
Decreases it
What are tight intercellular junctions called in cerebral capillaries?
The blood brain barrier
What are cerebral capillaries highly permeable to?
O2 and CO2
How does glucose cross the blood brain barrier?
By facilitated diffusion using specific carrier molecules
What three hydrophilic substances is the blood brain barrier exceptionally impermeable to?
- Ions
- Catecholamines
- Proteins
What are the metabolic needs of the airways met by?
Systemic bronchial circulation
What is pulmonary artery BP typically?
20-25/ 6-12 mmHg
What is the pulmonary capillary pressure like compared to the systemic cappilary pressure?
Low
What special adaptation of the pulmonary circulation protects against pulmonary oedema?
Absorptive forces exceed filtration forces
What causes vasoconstriction of pulmonary arterioles?
Hypoxia
Why is resting blood flow in skeletal muscle low?
Because of sympathetic vasoconstrictor tone
In relation to skeletal muscle blood flow: during exercise what overcomes sympathetic vasoconstrictor activity?
Metabolic hyperaemia
In skeletal muscle blood flow, what does circulating adrenaline cause?
Vasodilatation (beta-2-areniceptors)
What does contraction of muscle aid in relation to veins?
Venous return
What does skeletal muscle pump reduce the chance of?
Postural hypotension and fainting
What is the term for blood pooling in lower limb veins if venous valves become impotent?
Varicose veins
Why do varicose veins not lead to a reduction of CO?
Because of compensatory increase in blood volume
What is the term for the result of imparied vascular perfusion depriving the affected tissue of nutrients (including oxygen). It can be reversible on multiple factors including speed of onset, local demand and duration?
Ischaemia
What term refers to ischaemic necrosis of a dtissue or organ secondary to occlusion/reduction of the arterial supply or venous drainage. Recovery depends on a tissue regenerative ability?
Infarction
What is the term for a set of well regulated processes that accomplish functions (1. maintaing blood in a fluid, 2. induce rapid, localised haemostatic plug at site of vascular injury)?
Haemostasis
What is pathological/ corruption of haemostasis?
Thrombosis
What is the term for the formation of a solid or semi-solid mass from the constituents of blood, within the vascular system, during life?
Thrombosis
What are the three components of Virchow’s triad?
- Changes in vessel walls (endothelial injury)
- Changes in blood constituents (hypercoaguability)
- Changes in blood flow
What close small breaches in vessel walls and if activated in a vessel cause thrombus?
Platelets
Name the two components of platelets?
- Alpha granules (adhesion componenets, e.g. fibrinogen, fibronection, PDGF, anti-heparin)
- Dense granules (aggregation, ADP)
What do platelets cause when contacting collagen or fibrin?
Temporary patching
What maintains a permeability barrier and elaborates anticoagulant, antithrombotic, fibrinolytic regulators?
The endothelial cell
What four anticoagulant, antithrombotic and fibrinolytic regulators are elaborated in the endothelial cells?
- Prostacyclin
- Thrombomodulin
- Heparin-like molecules
- Plasminogen activator
What three prothrombotic molecules does the endothelial cell elaborate?
- VWF
- Tissue factor
- Plasminogen activator inhibitor
What does the endothelial cell use to modulate blood flow and vascular reactivity?
- Vasoconstrictors - endothelin, ACE
2. Vasodilators - NO, prostacylcin
What three substances are used in regulation of inflammation and immunity in the endothelial cell?
- IL-1, IL-6, chemokines
2. Adhesion molecules - VCAM-1, ICAM-1, E-selectin, P-selectin
Give three growth stimulators that regulate cell growth in endothelial cells?
- PDGF
- CSF
- FGF
Name two growth inhibitors that regulate cell growth in endothelial cells?
- Heparin
2. TNF-beta
What are important contributory factors in thrombosis that disrupt laminar blood flow?
Turbulence and stasis
What refers to any alteration in the coagulation pathway which predisposes to thrombosis?
Hypercoagulability
What two groups can conditions causing hypercoaguability be split into?
Acquired and Genetic
What are MI, immobilisation, tissue damage, cancer, prosthetic heart valves, DIC, heparin induced thrombocytopenia and antiphospholipid syndrome?
Acquired high risk hypercoaguable states
What are AF, cardiomyopathy, nephrotic syndrome, hyperoestrogenic states, oral contraceptive use, late pregnancy, sickle cell anaemia and smoking?
Lower risk aquired hypercoaguable states
Give three examples of genetic hypercoaguable states?
- Factor V mutations
- Defects in anticoagulant pathways - antithrombin III deficiency, protein C or S deficiency
- Defects in fibrinolysis
What show lines of Zahn?
Arterial thrombi
What two areas do mural thrombi take place?
Ventricles (heart) - MI, arrhythmias
Aorta (aneurysms) - atheroma
What thrombi are laminated due to alternating pale (platelet and fibrin) and dark (RBC/WBC) bands?
Mural thrombi
What is the term for a venous thrombi evoking inflammation?
Phlebothrombitis
What thrombi is most important in DVT of calf?
Venous thrombi (phlebothromboses)
What are large vessel thrombi prone to do?
Embolise
What thrombi form reddish/blue casts and are adherent to the wall?
Venosu thrombi
Give four fates of thrombi?
- Propagation proximally (small to large vessel)
- Embolisation
- Resolution (fibrinolysis)
- Organisation (granulation tissue, recanalisation)
What is the term for a detached intravascular solid, liquid ot gaseous mass which is carried by the bloodstream to a site distant from the point of origin?
Embolism
Name a fluid embolism?
Amniotic fluid embolism
What travels via IVC to pulmonary circulation?
Pulmonary thromboembolism
What can cause acute sudden death vs. segmental infarction (red infarcts), contrast with white infarcts?
Pulmonary thrombo embolism
How would you describe wedge shaped infarcts?
Wedge-shaped and firm
What is it important to remember in relation to venous emboli?
They do not cause infarcts in peripheral arterial circulation unless, atrial/ventricular septal defect, paradoxical embolus
What kind of embolism follows major soft tissue trauma and major bone fractures?
Fat embolism
Give two steps/features of fat emboli?
- Fatty marrow enters venules most globules arrest in lungs = dyspnoea
- Some reach peripheral circulation = skin rashes, CNS confusion
What embolism can result from barotrauma (occurs in divers) and during delivery/abortion or iatrogenic?
Gas/air embolism
How are vessels occluded in gas/air embolism?
Frothy bubbles occlude major vessels e.g. pulmonary artery
What embolism causes DIC (Disseminated intravascular coagulation), marked oedema and is post-partum?
Amniotic fluid embolism
How do amniotic fluid embolisms work?
Amniotic fluid and debris enters torn veins and embolises to lungs
What is a prostaglandin rich fluid?
Amniotic fluid
What three disease patterns is arteriosclerosis a generic term for?
- Atherosclerosis
- Monckeberg Medial Calcific Sclerosis
- Arteriosclerosis