Flashcards in Acute Coronary Syndrome Deck (21):
Spectrum of ACS
- Unstable angina
- Non-ST elevation myocardial infarction (NSTEMI)
- ST-elevation myocardial infarction (STEMI)
- Sudden cardiac death
What causes ACS?
- atherosclerotic plaque rupture or erosion
- superimposed platelet aggregation and thrombosis
- vasospasm, and vasoconstriction
- subtotal or transient total occlusion of vessel
What is the goal of pharmacotherapy?
Increase myocardial oxygen supply
- through coronary vasodilation
Decrease myocardial oxygen demand
- Decrease in heart rate
- Decrease in blood pressure
- Decrease preload or myocardial contractility
Features of ACS with STEMI
- Patients with STEMI have a high likelihood of a coronary thrombus occluding the infarct artery.
- Angiographic evidence of coronary thrombus formation is seen in more than 90% of patients with STEMI
How does STEMI usually occur in ACS
- STEMI usually occurs as a result of coronary artery occlusion due to formation of thrombus overlying an atheromatous plaque.
- If no PCI within 2 hours then thrombolysis is indicated.
What are thrombolytic agents and how do they work?
- Thrombolytic agents available today are serine proteases.
- They work by converting plasminogen to the natural fibrinolytic agent plasmin.
How does plasmin break down clots?
Plasmin lyses clot by breaking down the fibrinogen and fibrin contained in a clot
What are the types of thrombolytic agents?
Fibrinolytics are divided into two categories:
Non-fibrin specific agents:
What is the action of fibrin-specific agents?
They catalyse the conversion of plasminogen to plasmin in the absence of fibrin
What is the action of non-fibrin specific agents?
They catalyse systemic fibrinolysis
Contraindications to thrombolysis
- Prior intracranial haemorrhage (ICH)
- Known structural cerebral vascular lesion
- Known malignant intracranial neoplasm
- Ischaemic stroke within 3 months
- Suspected aortic dissection
- Active bleeding or bleeding diathesis (excluding menses)
- Significant closed-head trauma or facial trauma within 3 months
Benefits of thrombolysis
Timely thrombolysis is associated with:
- A 23% reduction in mortality
- A 39% reduction when used with aspirin
If there is no evidence of a STEMI, what treatment is given?
ACS medical treatment protocol
What treatment is involved in ACS medical treatment protocol?
- Fondaparinux/LMW heparin
- Intravenous nitrate
- Beta blockers
What is used in the management to reduce risk from NSTEMI?
- PCI or CABG
- Clopidogrel, prasugrel, ticagrelor, ticlopidine or cilostazol
- Heparin (LMWH)
- GIIb/IIIa receptor blockers
- Beta blockers
Antiplatelet Agents: aspirin
- Low dose aspirin (75-150mg)
- Aspirin is a potent inhibitor of platelet thromboxane A2 production
What does thromboxane do?
It stimulates platelet aggregation and vasoconstriction
What does the regular use of aspirin in acute MI do?
- Reduce mortality by 23%
- In combination with thrombolysis reduce mortality by 42% and reinfarction by 52%
What does the regular use of aspirin in unstable angina do?
- Reduce MI and death by 50%
What does the regular use of aspirin in secondary prevention do?
- Reduce reinfarction by 32% and combined vascular events by 25%.