Acute coronary syndrome is a constellation of symptoms and clinical findings which results from impaired cardiac perfusion at rest

Aetiology

• Usually the result of a thrombus from an atherosclerotic plaque blocking a coronary artery

Pathophysiology

• The mechanism that is common to all acute coronary syndromes is rupture or erosion of the fibrous cap of a coronary artery plaque
• This leads to platelet aggregation and adhesion, localized thrombosis, vasoconstriction and distal thrombus embolization
• Thrombus formation and the vasoconstriction produced by platelet release of serotonin and thromboxane A2 result in myocardial ischaemia due to reduction of coronary blood flow
• Myocardial infarction is caused by underperfusion of the myocardium leading to death of myocardial tissue
  • It is distinguished from angina by this death of tissue

Subtypes of ACS

• Unstable angina: subtotal occlusion, supply led ischaemia without infarction, high (50%) risk of MI in subsequent 30 days
• NSTEMI: subtotal occlusion
• STEMI: complete occlusion

Types of MI

• Type 1: Traditional MI due to an acute coronary event
• Type 2: Ischaemia secondary to increased demand or reduced supply of oxygen (e.g. secondary to severe anaemia, tachycardia or hypotension)
• Type 3: Sudden cardiac death or cardiac arrest suggestive of an ischaemic event
• Type 4: MI associated with PCI/coronary stunting/CABG

Clinical features

Symptoms

• Chest pain (SOCRATES)
  • Site - central/left sided
  • Onset - often sudden
  • Character - crushing ('like someone is sitting on your chest')
  • Radiation - left arm, neck and jaw
  • Associated symptoms - nausea, sweating, clamminess, shortness of breath, sometimes vomiting or syncope
  • Timing - constant, 30 mins or longer
  • Exacerbating/relieving factors - worsened by exercise/exertion and may be improved by GTN (but not completely relived or else angina)
  • Severity - Often extremely severe