How is unstable angina classified and what are the typical management and treatment options?

Unstable Angina Classification and Management

Unstable angina is classified into three principal presentations: rest angina, new-onset severe angina, and increasing angina, with management requiring immediate hospitalization, antiplatelet therapy, and early risk stratification for potential invasive intervention. 1, 2

Classification of Unstable Angina

Principal Presentations

• Rest angina: Angina occurring at rest and prolonged, usually greater than 20 minutes 1
• New-onset angina: New-onset angina of at least Canadian Cardiovascular Society (CCS) class III severity (within 2 months of presentation) 1, 2
• Increasing angina: Previously diagnosed angina that has become distinctly more frequent, longer in duration, or lower in threshold (increased by 1 or more CCS class to at least CCS class III severity) 1

Canadian Cardiovascular Society Classification

• Class I: Angina occurs only with strenuous, rapid, or prolonged exertion; ordinary physical activity does not cause angina 1, 3
• Class II: Slight limitation of ordinary activity; angina occurs when walking rapidly, climbing stairs rapidly, walking uphill, or under emotional stress 1, 3
• Class III: Marked limitations of ordinary physical activity; angina occurs when walking 1-2 blocks on level ground or climbing one flight of stairs 1, 3
• Class IV: Inability to carry on any physical activity without discomfort—anginal symptoms may be present at rest 1, 3

Pathophysiological Mechanisms

• Reduced myocardial perfusion due to coronary artery narrowing caused by thrombus on disrupted atherosclerotic plaque (most common cause) 1
• Dynamic obstruction (coronary spasm or vasoconstriction) 1
• Severe coronary narrowing without spasm or thrombus 1
• Coronary artery dissection 1
• Secondary unstable angina due to conditions that increase myocardial oxygen demand or reduce supply 1

Management of Unstable Angina

Immediate Management

• Immediate hospitalization with continuous ECG monitoring for ischemia and arrhythmia detection 2
• Antiplatelet therapy:
  • Aspirin 75-325 mg/day 2
  • Consider dual antiplatelet therapy based on risk stratification 2
• Anticoagulation with unfractionated heparin or low-molecular-weight heparin (enoxaparin preferred) 2
• Anti-ischemic therapy:
  • Nitrates for symptom relief 1
  • Beta-blockers (e.g., metoprolol) to reduce myocardial oxygen demand, but use cautiously in patients with heart failure 4
  • Calcium channel blockers (e.g., amlodipine) particularly effective for vasospastic angina 5

Risk Stratification

• Early risk stratification using:
  • Clinical criteria (age, risk factors, prior coronary disease) 2
  • ECG changes (ST-segment depression, T-wave inversion) 2
  • Cardiac biomarkers (troponin elevation indicates higher risk) 6
• Troponin status significantly impacts prognosis - troponin-positive patients have up to 20% risk of death or MI within 30 days compared to <2% in troponin-negative patients 6

Invasive vs. Conservative Strategy

• Early invasive strategy (coronary angiography within 24-48 hours) recommended for:
  • High-risk patients (recurrent angina, dynamic ECG changes, elevated troponins) 2
  • Intermediate-risk patients with multiple risk factors 2
• Conservative strategy may be appropriate for low-risk patients with negative biomarkers and no recurrent symptoms 2

Revascularization Options

• Percutaneous Coronary Intervention (PCI):
  • Effective with improved outcomes when combined with dual antiplatelet therapy 2
  • Indicated for patients with CCS class I-IV angina despite medical therapy with single-vessel disease 3
• Coronary Artery Bypass Grafting (CABG):
  • Preferred for diabetic patients with multivessel disease 2
  • Indicated for left main stem disease, three-vessel disease with objective large ischemia 3

Long-term Management and Follow-up

Secondary Prevention

• Aggressive risk factor modification:
  • Smoking cessation 3, 2
  • Lipid management 3
  • Diabetes management 3
  • Weight management and physical activity 3
• Optimal medical therapy:
  • Antiplatelet agents 2
  • Beta-blockers 4
  • Statins 2
  • ACE inhibitors/ARBs for patients with left ventricular dysfunction 2

Follow-up Schedule

• High-risk patients: Return in 1-2 weeks 2
• Lower-risk patients: Return in 2-6 weeks 2
• Regular outpatient follow-up to assess symptom control and optimize medical therapy 2

Common Pitfalls and Caveats

• Failure to recognize unstable angina as a medical emergency requiring hospitalization 2
• Delaying antiplatelet therapy in unstable angina patients 2
• Inadequate risk stratification, particularly overlooking the prognostic value of troponin status 6
• Abrupt discontinuation of beta-blockers in patients with coronary artery disease can cause severe exacerbation of angina, myocardial infarction, and ventricular arrhythmias 4
• Overlooking the importance of secondary prevention measures 2
• Failure to recognize vasospastic angina, which may require calcium channel blockers as primary therapy rather than beta-blockers 5