Angina Pectoris – Pathogenesis

Definition & Etymology:

• Angina means “strangle” in Greek; pectoris refers to the chest.
• Represents episodes of chest pain caused by transient myocardial ischemia (lack of oxygen in the heart muscle).

Normal Response to Increased Demand:

• During activities like exercise, the heart increases blood flow via vasodilation to meet higher oxygen needs.
• Sympathetic stimulation:
  • Speeds heartbeat and increases contractility.
  • Blood flow to skeletal muscles increases.
• Local autoregulation:
  • Senses lower oxygen and higher CO₂, triggering vasodilation to increase blood flow and oxygen delivery to the heart.

Causes of Reduced Myocardial Perfusion:

• Atherosclerotic plaque:
  • Narrows the lumen, reducing blood flow and oxygen supply.
• Coronary artery spasm:
  • Sudden, transient narrowing that impairs blood flow temporarily.
• Blood problems:
  • Anemia (e.g., iron deficiency or sickle cell anemia):
    • Decreased hemoglobin reduces oxygen transport capacity.
  • Sickle cell anemia:
    • Hemoglobin mutation causes sickle-shaped cells, disrupting oxygen delivery.
• Lung problems:
  • Inadequate gas exchange or decreased oxygenation in the lungs.
• Myocardial hypertrophy:
  • Thickening of the heart wall (pathologic hypertrophy) occurs in response to high blood pressure and increased workload.
  • Wall thickening supports the heart under stress but reduces blood vessel growth (angiogenesis)—leading to poor oxygen supply to the myocardium over time.

Pathophysiological Summary:

• When perfusion cannot meet demand, ischemia occurs → angina pectoris (chest pain).
• Ischemia may be short-lived if vessels dilate again, or prolonged if the obstruction persists.

Implications of Hypertrophy:

• The heart grows thicker to compensate but may outgrow its blood supply, leading to chronic ischemia and increased risk for heart failure.

Key Concepts of Poor Cardiac Perfusion:

• Transient blockage or inadequate perfusion leads to chest pain.
• Causes include vessel narrowing, spasm, anemia, lung issues (resulting in poor blood oxygenation), and pathologic hypertrophy.
• Chronic (pathologic) hypertrophy can degenerate into heart failure due to insufficient oxygenation, despite the thickened muscle trying to compensate.

3 Types of Angina:

1.  Classic or Exertional Angina:

• Most common type.
• Triggered by physical activity or exertion.
• Example scenario: Grandpa goes for a run, experiences chest pain because increased oxygen demand cannot be met due to narrowed or damaged coronary arteries.
• Mechanism: During exertion, the heart beats faster and demands more oxygen; if arteries cannot vasodilate sufficiently, ischemia occurs.

2.  Variant Angina (Vasospastic Angina):

• Occurs even at rest.
• Caused by spasm of coronary arteries, temporarily narrowing or constricting blood flow.
• Example: Grandpa sitting on the couch and suddenly experiencing chest pain due to arterial spasm.
• Mechanism: Blood vessel spasm reduces or halts blood flow despite normal activity levels.

3.  Unstable Angina:

• The most dangerous type.
• Characterized by prolonged, persistent chest pain.
• Can worsen over time, potentially leading to myocardial infarction (heart attack).
• Cause: Often due to plaque rupture with thrombus formation, causing abrupt and severe obstruction.
• This type often requires emergency intervention.

Symptoms:

• • Recurrent episodes of substernal chest pain.
  • • Descriptions: “feels like being kicked by a horse” or sat-on by an elephant.
    • Can radiate to the left arm.
  • Pain often occurs with physical exertion or emotional stress.
  • Severity and duration depend on the extent of blockage.
• Behavioral Response:
  • Grandpa reduces activity to relieve pain.
  • With ongoing atherosclerosis, plaques grow larger, leading to more frequent and longer attacks.

Diagnostic and Immediate Actions:

• When someone like Grandpa experiences angina symptoms, a doctor will conduct diagnostic tests (blood tests, ultrasound, angiography) to confirm the cause.
• Emergency response:
  • Call 911 if pain persists longer than 5 minutes or if it’s the first attack.
  • Do not assume it’s just angina; it could be a myocardial infarction requiring urgent care.

Pharmacological Treatment: Vasodilators (e.g., Nitroglycerin):

• Mechanism: Mimics nitric oxide, a natural potent vasodilator.
• Forms:
  • Sublingual tablet (dissolves quickly).
  • Patch (applied to skin).
  • Oral spray.
• Action:
  • Mainly reduces systemic resistance.
  • Lowers heart’s oxygen demand by decreasing workload.
• Usage in attack:
  • Sit upright, stay calm.
  • Take nitroglycerin at the onset of chest pain.
  • Can take repeated doses if pain persists, typically up to three doses.
  • If pain lasts longer than 10-15 minutes or doesn’t resolve after multiple doses, seek emergency care.

Precautions and Lifestyle Advice:

• Avoid stressors:
  • Cold or hot weather, pollution, large meals, physical exertion.
• Diet:
  • Eat smaller, more frequent meals to reduce cardiac stress.
• Carry medication:
  • Remember to take nitroglycerin if diagnosed.
• Risks of untreated angina:
  • Prolonged ischemia (>3-5 min) can cause heart cell death leading to a heart attack.
  • Recurring episodes increase risk of myocardial infarction.

Summary:

Angina pectoris results from an imbalance between oxygen demand and supply, often due to narrowing or spasm of coronary arteries, anemia, or hypertrophy. Effective treatment involves relieving ischemia and managing underlying causes to prevent progression to ischemic heart disease or heart failure.

Angina pectoris manifests as intermittent chest pain caused by temporary coronary artery compromise. Types vary based on triggers and severity, from exertional to spontaneous vasospasms and unstable episodes at risk for MI. Progressive plaque buildup makes these episodes more frequent and severe, underscoring the importance of early diagnosis and management.

Immediate management of angina involves vasodilators like nitroglycerin, lifestyle modifications, and prompt medical intervention if symptoms are severe or persistent. Avoiding triggers and stressors can prevent recurrent attacks and progression to myocardial infarction. Recognizing symptoms early and acting swiftly is key to preserving heart tissue