Lecture 9.1a - Ischemic heart disease - pathophysiology

Ischemic Heart Disease

• Ischemic heart disease is caused by a reduced oxygen supply to the heart, often due to atherosclerotic plaques in the coronary vessels, embolus, or vasospasms.
• Increased oxygen demand can also contribute to ischemic heart disease, triggered by factors such as tachycardia, left ventricular hypertrophy, or exertion.

Risk Factors for Coronary Atheroma

• Modifiable risk factors:
  • BMI > 30
  • Diabetes mellitus
  • Hypertension
  • Tobacco use
  • Increased LDL/decreased HDL
  • Ethanol consumption
• Non-modifiable risk factors:
  • Age > 65 years
  • Relatives with CAD/family history

Classifications of Ischemic Heart Disease

• Stable angina:
  • Caused by stable atherosclerotic plaques
  • Pain occurs during exertion
  • Subendocardial ischemia
• Unstable angina:
  • Caused by plaque rupture and thrombus formation
  • Pain occurs at rest or progresses rapidly over a short period
  • Subendocardial ischemia
• Subendocardial infarction (NSTEMI):
  • Ischemia for longer than 30 minutes leads to infarction (cell death)
  • Pain occurs at rest or progresses rapidly over a short period
  • Subendocardial infarction
• Transmural infarction (STEMI):
  • Complete occlusion of blood vessel lumen and infarct of the entire thickness of the myocardium
  • Pain occurs at rest or progresses rapidly over a short period
  • Transmural infarction

Clinical Features of Ischemic Cardiac Chest Pain

• Typical:
  • Discomfort/pressure (dull, crushing) lasting > 2 minutes
  • Provoked by activity/exercise
  • Radiation (arms, jaws)
  • Does not change with respiration/position
  • Associated with sweating/nausea
  • Relieved by rest/nitroglycerin
• Atypical:
  • Pain localised with one finger
  • Constant pain lasting for a few days
  • Fleeting pains lasting for a few seconds
  • Pain reduced by movement/palpation
  • No pain (diabetes mellitus, elderly, post heart transplant)

Pathophysiology and Clinical Features

• Right ventricular MI:
  • Jugular venous distension
  • Oedema (lower extremities)
  • Hepatomegaly
  • Ascites
  • Hypotension
  • Clear lungs
  • Bradycardia/AV block
• Left ventricular MI:
  • Pulmonary oedema
  • Shortness of breath
  • Hypotension
  • S4 heart sound
  • Reflex tachycardia

MI Complications

• 0-24 hours:
  • Sudden cardiac death
  • Acute heart failure
• 24 hours-3 days:
  • Pericarditis
  • Inflammation
  • Frictional rub
  • Pericardial effusion
• 3-14 days:
  • Rupture syndromes
  • Ventricular septal defect
  • Free wall rupture -> cardiac tamponade
  • Papillary muscle rupture -> mitral regurgitation
• 14 days-months:
  • LV aneurysms
  • Risk of thrombus formation

Pericarditis

• Inflammation of the pericardium often due to a viral illness
• Causes retrosternal, sharp, and localised chest pain
• A pericardial rub may be heard on auscultation of the chest
• Saddle-shaped ST elevations may be present in an ECG