Cardiology

• What is the definition of acute coronary syndrome (ACS)?

  The suspicion or confirmed presence of acute myocardial ischaemia
• What are the categories of acute coronary syndrome (ACS)?

  • Non-ST Elevation ACS
  • NSTEMI: infarction with positive myocardial injury biomarkers
  • Unstable angina: absence of detectable myocardial injury biomarkers, ischaemia chest pain at rest or minimal exertion
  • ST Elevation ACS: acute coronary syndrome manifesting with ST elevations on ECG
• What is myocardial infarction (MI) defined as?

  Acute myocardial injury with clinical and diagnostic evidence of acute ischaemia
• How is myocardial infarction classified?

  • Type 1: Caused by atherosclerotic plaque disruption or acute coronary thrombosis
  • Type 2: Secondary to an oxygen supply/demand mismatch
  • Type 3: Resulting in death when biomarker values are unavailable
  • Type 4: Related to percutaneous coronary intervention
  • 4a: MI ≤ 48 hours after PCI
  • 4b: MI related to stent thrombosis
  • 4c: MI associated with restenosis after PCI
  • Type 5: Related to coronary artery bypass grafting
• What is the most common form of myocardial infarction?

  Type 1 myocardial infarction
• What causes Type 1 myocardial infarction?

  Acute thrombosis due to erosion, ulceration, fissuring, dissection, or rupture of an atherosclerotic plaque
• What is the consequence of decreased myocardial blood flow in Type 1 MI?

  Sudden death of myocardial cells
• What is the prevalence of Type 2 myocardial infarction?

  Less common form (14%)
• In which population does Type 2 myocardial infarction predominantly occur?

  In women and individuals with co-morbidities
• What is the cause of ischaemia in Type 2 myocardial infarction?

  Increased oxygen demand or decreased coronary blood supply
• What is Type 3 myocardial infarction characterized by?


  MI resulting in death when biomarker values are unavailable
• What is Type 4 myocardial infarction related to?

  Percutaneous coronary intervention
• What are the subtypes of Type 4 myocardial infarction?

  4a: MI ≤ 48 hours after PCI, 4b: MI related to stent thrombosis, 4c: MI associated with restenosis after PCI
• What is Type 5 myocardial infarction related to?

  Coronary artery bypass grafting
• What is the most common cause of myocardial infarction?

  Coronary artery disease
• What are some conditions that can lead to myocardial ischaemia and infarction?

  • Coronary artery disease
  • Coronary artery vasospasm
  • Coronary artery dissection
  • Coronary artery embolism
  • Takotsubo cardiomyopathy
  • Myocarditis
  • Thrombophilia
  • Vasculitis
  • Myocardial oxygen supply-demand mismatch
• What are the risk factors for myocardial infarction?

  • Smoking
  • Diabetes mellitus
  • Obesity
  • Hypertension
  • Hyperlipidaemia
• What happens during partial coronary artery occlusion?

  • Decreased myocardial blood flow
  • Supply-demand mismatch
  • Myocardial ischaemia
  • Usually affects the inner layer of the myocardium (subendocardial infarction)
• What occurs during complete coronary artery occlusion?

  • Impaired myocardial blood flow
  • Sudden death of myocardial cells if no reperfusion occurs
  • Usually affects the full thickness of the myocardium (transmural infarction)
• What characterizes unstable atherosclerotic plaques?

  • Lipid-rich
  • Covered by thin fibrous caps
  • High risk of rupture and acute coronary syndrome
• What is the role of inflammatory cells in atherosclerotic plaque disruption?

  They secrete matrix metalloproteinases that weaken the fibrous cap, leading to rupture
• What can cause oxygen supply and demand mismatch in Type 2 MI?

  • Decreased oxygen supply: occlusion of coronary arteries, reduced perfusion
  • Increased oxygen demand: sustained tachyarrhythmia
• What is the classic presentation of myocardial infarction?

  Acute retrosternal chest pain
• What are the characteristics of the chest pain associated with myocardial infarction?

  Dull, squeezing pressure and/or tightness, commonly radiating to left chest, arm, shoulder, neck, jaw, and/or epigastrium
• What can precipitate the chest pain in myocardial infarction?


  Exertion or stress
• What is the peak time of occurrence for myocardial infarction symptoms?

  Usually in the morning
• What are some other clinical features of myocardial infarction?

  Dyspnoea, pallor, nausea, vomiting, diaphoresis, anxiety, dizziness, lightheadedness, syncope
• What are atypical presentations of myocardial infarction?

  • More likely in elderly, diabetic individuals, and women
  • Stabbing, sharp chest pain
  • No or minimal chest pain
  • Epigastric pain
  • Autonomic symptoms (e.g., nausea, diaphoresis, syncope)
• What is the clinical triad in right ventricular infarction?

  Hypotension, elevated jugular venous pressure, clear lung fields
• What is the best initial test for suspected acute coronary syndrome?

  • 12-lead ECG
• What are the findings in the acute stage of STEMI on ECG?

  • Hyperacute T waves (peaked T wave)
  • ST elevations in two contiguous leads with reciprocal ST depressions
  • New onset left bundle branch block
• What are the findings in the intermediate stage of myocardial necrosis on ECG?

  • Absence of R wave
  • T-wave inversions
  • Pathological Q waves
  • Duration ≥ 0.04 seconds
  • Amplitude ≥ ¼ of the R wave or ≥ 0.1 mV
  • Any Q wave in leads V1–3
• What are the findings in the chronic stage of myocardial infarction on ECG?

  • Persistent, broad, and deep Q waves
  • Often incomplete recovery of R waves
  • Permanent T-wave inversion is possible
• What are the ECG changes in NSTEMI/unstable angina?

  • No ST elevations present
  • Nonspecific signs of ischaemia may be present, including:
  • ST depression
  • Transient ST deviations
  • T-wave inversions
  • Poor R wave progression
• What is the most important biological marker of myocardial necrosis?

  Cardiac troponin
• What is the repeat interval for cardiac troponin testing?

  • Conventional assay: 3–6 hours
  • High-sensitivity troponin (hscTn): 1–3 hours
• What indicates STEMI/NSTEMI elevation in troponin testing?

  Elevation > 99th percentile PLUS change ≥ 20% on repeat testing
• How long does it take for troponin to normalize after myocardial infarction?

  1. 10 days
• What are the characteristics of cardiac troponin?

  • Cardiac-specific marker with high sensitivity for myocardial necrosis
  • Degree of elevation correlates with the size of the infarct and risk of mortality
• What routine studies are performed in suspected myocardial infarction?

  • FBC and markers of inflammation
  • Serum chemistries
  • Coagulation panel
  • Urine toxicology screening