Unstable Angina

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Patient Advice

Definition

Unstable Angina is a type of acute coronary syndrome (ACS) characterised by chest pain or discomfort caused by reduced blood flow to the heart. Unlike myocardial infarction, unstable angina does not cause detectable heart muscle damage or elevated troponin levels.

Aetiology

The underlying cause of unstable angina is typically atherosclerosis with plaque rupture or erosion leading to partial arterial occlusion.

• Thrombus Formation: Partial obstruction of the coronary artery by a blood clot.
• Coronary Vasospasm: Sudden narrowing of the coronary artery.
• Severe Anaemia: Reduces oxygen delivery to the heart.

Pathophysiology

Unstable angina develops due to:

• Plaque Disruption: Rupture or erosion of an atherosclerotic plaque exposes pro-thrombotic material, leading to thrombus formation.
• Reduced Coronary Blood Flow: Partial obstruction decreases oxygen delivery to the myocardium.
• Myocardial Ischaemia: Lack of oxygen leads to angina symptoms without permanent damage to the heart muscle.

Risk Factors

Key risk factors for unstable angina include:

• Age (older adults).
• Smoking and excessive alcohol intake.
• Hypertension and hyperlipidaemia.
• Diabetes mellitus.
• Family history of coronary artery disease.
• Obesity and sedentary lifestyle.

Signs and Symptoms

Common features of unstable angina include:

• Chest Pain: Typically central, crushing, or tight, lasting longer than 10 minutes and not relieved by rest or nitrates.
• Radiation: Pain may radiate to the jaw, neck, arms, or back.
• Dyspnoea: Shortness of breath due to myocardial ischaemia.
• Fatigue and Sweating: Often associated with anxiety or distress.
• Palpitations: Due to increased heart rate or arrhythmias.

Investigations

Diagnostic tests and expected findings include:

• Electrocardiogram (ECG):
  • May show ST-segment depression or T-wave inversion during pain episodes.
  • Normal ECG does not exclude unstable angina.
• Troponin Levels: Not elevated in unstable angina, distinguishing it from myocardial infarction.
• Blood Tests:
  • Full Blood Count (FBC): To rule out anaemia or infection.
  • Renal Function and Electrolytes: For baseline assessment before treatment.
  • Lipid Profile: To evaluate cardiovascular risk.
• Coronary Angiography: May be required to assess the extent of coronary artery disease.

Management

1. Acute Management

• Oxygen Therapy: For hypoxia.
• Nitrates: Sublingual glyceryl trinitrate (GTN) to relieve chest pain.
• Antiplatelet Therapy: Aspirin (300 mg loading dose) and clopidogrel to prevent thrombus formation.
• Anticoagulation: Low molecular weight heparin (e.g., enoxaparin) to reduce clot progression.
• Beta-blockers: E.g., bisoprolol to reduce myocardial oxygen demand.

2. Secondary Prevention and Chronic Management

• Statins: E.g., atorvastatin to lower cholesterol and stabilise plaques.
• ACE Inhibitors: E.g., ramipril for cardiovascular protection.
• Dual Antiplatelet Therapy (DAPT): Aspirin and clopidogrel for at least 12 months.
• Smoking Cessation Support: To reduce future cardiovascular risk.

3. Specialist Referral

Referral to a cardiology team is essential for further evaluation and consideration of invasive interventions such as percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG).

Patient Advice

Key advice includes:

• Avoid strenuous activity until stable.
• Carry glyceryl trinitrate (GTN) spray for symptom relief.
• Adhere to prescribed medications and attend follow-up appointments.
• Adopt a heart-healthy lifestyle, including a balanced diet and regular exercise as tolerated.
• Seek urgent medical attention if chest pain persists or worsens.