Define ACS
A spectrum of acute myocardial ischaemic states due to unstable plaque rupture and thrombosis in the epicardial coronary artery leading to reduced blood flow.
What are the the 3 major clinical subtypes of ACS?
- Unstable angina
- Non-ST segment elevation myocardial infraction (NSTEMI)
- ST- segment elevation myocardial infraction (STEMI)
What is unstable angina?
unstable plaque rupture and thrombosis leading to transient occlusion of artery.
What is NSTEMI?
- unstable plaque rupture and thrombosis leading ton partial occlusion of artery,
- enzymatic evidence of myocardial cell necrosis
What is STEMI?
- unstable plaque rupture and thrombosis leading to complete occlusion of artery and sustained myocardial ischaemi and cell necrosis
- electrical instability and cardiac arrhythmias increase risk of sudden cardiac death
Describe the major clinical features of ACS.
- Persistent chest pain that radiates to neck/arms/jaw
- Breathlessness/dizziness due to ischaemia-induced LV dysfunction and cardiac arrhythmias
- Serial ECG changes: ST-segment depression/elevation, T-wave inversion, pathological P wave development
Serial cardiac biomarks: serum myoglobin, CK-MB, troponin, myocardial cell necrosis
What are the ECG changes seen in unstable angina and NSTEMI?
- persistent in NSTEMI
- transient in unstable angina
- ST-segment depression
- T-wave inversion
What are the ECG changes seen in STEMI?
- persistent ST-segment elevation
- pathological Q waves development
Describe the diagnosis of ACS
- eliminate ACS secondary to obstructive CAD
- determine patients’ 6 month risk of adverse CV events
- clinical assessment: full history, physical examination, cardiac biomarker changes and ECG
What is the non-pharmacological management of ACS?
- mechanical reperfusion - revascularisation with PIC/CABG
Describe the immediate clinical management of STEMI?
- aspirin 300mg PO stat/ clopidogrel if intolerant
- antiplatelet/anticoagulant
- supplemental O2 if SaO2 is more than 94%
- GTN
- morphine/diamorphine IV for pain
- BB IV
What is the difference between the anti thrombotic and pro thrombotic system?
Anti thrombotic system - inactivities clotting factors and plasminogen fibrinolytic system dissolves blood clots.
Pro thrombotic system - platelet adhesion and aggregation and activation of coagulation cascade forms blood clots.
Give 2 named examples of anti platelet drugs used in ACS management.
Aspirin
Clopidogrel
What is the mechanism of action for the anti platelet drug Aspirin?
it inhibits the COX enzyme - inhibiting TXA2 synthesis to inhibit platelet activation and aggregation in response to plaque rupture.
What is the mechanism of action for the anti platelet drug Clopidogrel?
inhibits ADP-R inhibiting platelet activation and aggregation in response to plaque rupture
Give 2 named examples of anti coagulant drugs used in ACS management.
UF heparin
Bivalrudin
What is the mechanism of action for the anti coagulant drug UF heparin?
indirect thrombin inhibitor - activates anti thrombotic system which inactivates FIIa, FXa, FIXa inhibiting the coagulation cascade.
What is the mechanism of action for the anti coagulant drug Bivalrudin?
Direct thrombin inactivator - inactivates FIIa
Give named examples of the 2 classes of thrombolytic drugs and describe their mechanism of action for thrombolytic therapy used in ACS management.
Activation of plasminogen fibrinolytic system to dissolve blood clot in infarct-related coronary artery and restore blood flow.
SK - indirectly-acting plasminogen activator
T-PAs - directly acting plasminogen activators - alteplase, reteplase, tenecteplase
Clot selective and fibrin-enhanced conversion of plasminogen to plasmin
What are the adverse effects of thrombolytic drugs?
haemorrhage
hypotension
allergic reaction
reperfusion induced arrhythmias
Describe the pathway summary for unstable angina and NSTEMI
- 300mg aspirin
- anti thrombin therapy
- assess LV function
Describe the pathway summary for STEMI
- 1st line - PCI within 120 mins of diagnosis
- Aspirin AND clopidogrel
- Assess LV function
