Acute Coronary Syndrome

Question 1

Spectrum of ACS

Answer 1

• Unstable angina
• Non-ST elevation myocardial infarction (NSTEMI)
• ST-elevation myocardial infarction (STEMI)
• Sudden cardiac death

Question 2

What causes ACS?

Answer 2

Common pathogenesis

• atherosclerotic plaque rupture or erosion
• superimposed platelet aggregation and thrombosis
• vasospasm, and vasoconstriction
• subtotal or transient total occlusion of vessel

Question 3

What is the goal of pharmacotherapy?

Answer 3

Increase myocardial oxygen supply
- through coronary vasodilation

Decrease myocardial oxygen demand

• Decrease in heart rate
• Decrease in blood pressure
• Decrease preload or myocardial contractility

Question 4

Features of ACS with STEMI

Answer 4

• 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

Question 5

How does STEMI usually occur in ACS

Answer 5

• 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.

Question 6

What are thrombolytic agents and how do they work?

Answer 6

• Thrombolytic agents available today are serine proteases.

- They work by converting plasminogen to the natural fibrinolytic agent plasmin.

Question 7

How does plasmin break down clots?

Answer 7

Plasmin lyses clot by breaking down the fibrinogen and fibrin contained in a clot

Question 8

What are the types of thrombolytic agents?

Answer 8

Fibrinolytics are divided into two categories:
Fibrin-specific agents:
- Alteplase 
- Reteplase 
- Tenecteplase

Non-fibrin specific agents:
- Streptokinase

Question 9

What is the action of fibrin-specific agents?

Answer 9

They catalyse the conversion of plasminogen to plasmin in the absence of fibrin

Question 10

What is the action of non-fibrin specific agents?

Answer 10

They catalyse systemic fibrinolysis

Question 11

Contraindications to thrombolysis

Answer 11

• 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

Question 12

Benefits of thrombolysis

Answer 12

Timely thrombolysis is associated with:

• A 23% reduction in mortality
• A 39% reduction when used with aspirin

Question 13

If there is no evidence of a STEMI, what treatment is given?

Answer 13

ACS medical treatment protocol

Question 14

What treatment is involved in ACS medical treatment protocol?

Answer 14

• Aspirin
• Tigagrelor/Clopidogrel
• Fondaparinux/LMW heparin
• Intravenous nitrate
• Analgesia
• Beta blockers
• Statins

Question 15

What is used in the management to reduce risk from NSTEMI?

Answer 15

• PCI or CABG
• Aspirin
• Clopidogrel, prasugrel, ticagrelor, ticlopidine or cilostazol
• Heparin (LMWH)
• Fondaparinux
• GIIb/IIIa receptor blockers
• Statins
• Beta blockers

Question 16

Antiplatelet Agents: aspirin

Answer 16

• Low dose aspirin (75-150mg)

- Aspirin is a potent inhibitor of platelet thromboxane A2 production

Question 17

What does thromboxane do?

Answer 17

It stimulates platelet aggregation and vasoconstriction

Question 18

What does the regular use of aspirin in acute MI do?

Answer 18

• Reduce mortality by 23%

- In combination with thrombolysis reduce mortality by 42% and reinfarction by 52%

Question 19

What does the regular use of aspirin in unstable angina do?

Answer 19

• Reduce MI and death by 50%

Question 20

What does the regular use of aspirin in secondary prevention do?

Answer 20

• Reduce reinfarction by 32% and combined vascular events by 25%.

Question 21

What is Clopidogrel and what does it do?

Answer 21

• Clopidogrel is a prodrug
• Inhibits ADP receptor activated platelet aggregation
• Specifically and irreversibly inhibits the P2Y12 ADP receptor which is important in aggregation of platelets and cross-linking by fibrin