Acute Coronary Syndromes Flashcards
What is the fundamental difference between stable angina and acute coronary syndrome?
in ACS blood vessels are not just partially blocked by an atherosclerotic plaque, there is also involvement of a blood clot (thrombus)
What are the three disorders the term ACS covers?
Unstable angina
NSTEMI: non ST (interval in ECG) elevated myocardial infarction
STEMI: ST elevated myocardial infarction
What are ACS disorders characterised by?
- A group of disorders characterised by severe chest pain radiating to left arm and jaw
- Not relieved by rest – lasts more than a few minutes
How does an ECG help us classify what type of ACS we have?
- elevation of ST interval tells us we are dealing with a STEMI (most serious)
- ST inversion, depression or no change tells us we are probably dealing with an NSTEMI or unstable angina
How do you differentiate between an NSTEMI or unstable angina?
You look for blood markers (proteins only present in cardiac tissues) to differentiate between NSTEMI or unstable anginas
If you detect a blood marker it is an NSTEMI if not it is unstable angina
What are the different treatment methods for ACS?
- reduce pain
- reduce cardiac workload (to reduce pain caused by ischaemia)
- prevent further thrombosis
- reperfusion
What is given for pain in ACS?
opioids
What is given to reduce cardiac workload?
Beta blocker: same as in stable angina (also helps overcome sympathetic nervous system activation)
GTN (also reduces pain)
What is given to prevent further thrombosis?
Aspirin (antiplatelet drugs)
Ticagrelor/ clopidogrel (antiplatelet drugs)
Heparins (anticoagulants)
Atorvastatin (stops atherosclerosis from progressing)
What is given to restore blood supply?
PCI
CABG (if PCI not done straight away)
Thrombolysis (breaking down the thrombus – drug approach)
What happens in haemostasis (blood clotting)?
- Prevention of blood loss after vessel damage
- Coagulation, platelet aggregation
- Vasoconstriction
What are types of thrombosis and is it useful or pathological?
- Pathological
- DVT (deep vein thrombosis), Embolism, Stroke, heart attack
What is a thrombus and what does it do?
- Fibrin framework
- Traps platelets, other blood cells
- Attached to vessel wall
Impedes blood flow
Reduces perfusion of tissues
Can cause heart attack (or stroke)
What has a major role in venous thrombosis?
Coagulation
What has a more important role in arterial thrombosis?
- Platelet aggregation has a more important role
- Coagulation also involved
What may influence the drug being used in thrombosis?
whether it is venous or arterial
What is an embolus, what are the different types and what do they do?
- Fragment or whole thrombus detached from vessel wall
- Travels through vessels
- Blocks small vessels in pulmonary, cardiac, CNS circulation
Pulmonary embolism (from venous thrombus)
Myocardial infarction
Stroke
Limb infarction
Why is the formation of thrombosis very serious?
- Lib infarction – can lose a whole limb
- Pulmonary embolism, stroke heart attack can be fatal
What are the targets for modifying thrombosis processes?
- Modify coagulation Most successful in venous thrombosis - Modify platelet aggregation Important in arterial thrombosis - Modify clot, thrombus breakdown After prophylaxis fails
What happens in coagulation?
- Proteolytic enzymes act on other modules in the cascade to convert them from the active form to the inactive form
- IX -> IXa
- VIIa -> VII
- Thrombin acts of fibrinogen to turn it into fibrin
What are Heparins?
- Family of Sulphated Mucopolysaccharides
Have a sugar backbone and have sulphate groups attached to them - Repeating groups with high -ve charge (because of sulphate groups) - essential for activity
Where are heparins present?
in the liver, lungs and mast cells
What is the molecular weight of heparins?
- Varying MW, 3-40K
Heparin, Standard -> unfractionated – not purified, variable molecular weight
Low MW heparins – uses purification techniques
Enoxaparin (fondaparinux)
Action varies between the two
What is thrombin, what does it do and how is it formed?
- Proteolygtic enzyme
- Cleaves soluble fibrinogen to insoluble fibrin
- Active thrombin (IIa) is produced by cleavage of prothrombin (II) by Factor Xa
- Factor Xa is produced from Factor X (inactive) by both Factor IXa and Factor VIIa