Acute coronary syndrome (ACS)

• ☂️ ACS is an umbrella term covering a number of acute presentations of IHD:
  • ST elevation myocardial infarction (STEMI)
    • STEMI generally correlates with a ‘full thickness’ MI
    • Causes a rise in cardiac enzymes
  • Non-ST elevation myocardial infarction (NSTEMI)
    • NSTEMI generally correlates with a ‘partial thickness’ lesion or severe narrowing
    • Causes a rise in cardiac enzymes
  • Unstable angina
    • Does not cause a rise in cardiac enzymes

Causes and pathology of ACS

• ACS is caused by IHD
• IHD is the same as CHD and coronary artery disease
• Gradual build up of atherosclerotic plaques within arteries
• This causes two issues:
  1. Gradual narrowing of the coronary vessels
     • This means less blood (and therefore oxygen) can get to the myocardium
     • This can mean that when the myocardium has an increased oxygen demand (such as during exercise), chest pain (known as angina) occurs
  2. Risk of sudden plaque rupture
     • Atherosclerotic plaques which have built up in the endothelium may rupture, leading to sudden occlusion of the coronary artery
       • This is called thrombotic occlusion
       • When a thrombus forms in a fast flowing artery it is made up mostly of platelets
         • This is why anti-platelets are used
     • This can cause complete occlusion of the blood supply to a region of the myocardium, leading to infarction

The coronary arteries 🫀

• Two coronary arteries
  • LEFT
  • RIGHT
• LEFT
  • Divides into Circumflex and Left Anterior Descending (LAD).
• RIGHT
  • Curves around the right side and under the heart and supplies the:
    • Right atrium
    • Right ventricle
    • Inferior aspect of left ventricle
    • Posterior septal area

Risk factors🙇🏽

• Unmodifiable
  • Increasing age
  • Male sex
  • Family history
• Modifiable
  • Smoking
  • Diabetes mellitus
  • Hypertension
  • Hypercholesterolaemia
  • Obesity

Pathophysiology

Pathology of ACS (1)

NSTEMI:

• ST - Depression or T wave inversion