What are the diagnostic steps and treatment for stable angina?

Diagnosis of Stable Angina

The diagnosis of stable angina requires a systematic approach beginning with a detailed characterization of chest pain, followed by risk stratification with appropriate non-invasive testing, primarily exercise ECG testing for patients who can exercise and have interpretable ECGs. 1, 2

Clinical Evaluation

Chest Pain Characterization

• Typical angina meets all three criteria:
  • Retrosternal chest pain of characteristic quality (pressure, heaviness, squeezing)
  • Provoked by exertion or emotional stress
  • Relieved by rest or nitroglycerin within minutes 2
• Atypical angina meets two of these criteria
• Non-cardiac chest pain meets one or none of these criteria 2

Pretest Probability Assessment

• Estimate probability of CAD based on:
  • Age and sex
  • Characteristics of chest pain
  • Presence of risk factors (especially diabetes, hyperlipidemia, smoking) 1
• Patients can be classified as having low (<10-20%), intermediate, or high (>80-90%) probability of CAD 1

Diagnostic Testing Algorithm

Step 1: Initial Testing for All Patients

• Resting 12-lead ECG (mandatory in all patients with suspected stable angina) 1, 2
• Laboratory analysis: complete blood count, lipid profile, glucose, renal function 2

Step 2: Non-Invasive Testing

For patients with intermediate to high probability of CAD:

1. Exercise ECG testing (first-line) for patients who:

   • Can exercise
   • Have interpretable ECG (no preexcitation, paced rhythm, >1mm ST depression at rest, or complete LBBB) 1
   • Are not taking digoxin 1

2. Stress imaging tests (when exercise ECG is not suitable):

   • Stress echocardiography
   • Myocardial perfusion imaging (SPECT)
   • Stress cardiac MRI 1, 2

Step 3: Assessment of Left Ventricular Function

• Echocardiography or radionuclide imaging is indicated for patients with:
  • History of MI
  • Pathologic Q waves on ECG
  • Symptoms/signs of heart failure
  • Complex ventricular arrhythmias 1

Step 4: Coronary Angiography

• Consider for patients with:
  • Marked limitation of ordinary activity (Canadian Cardiovascular Society class III) despite maximal medical therapy 1
  • High-risk findings on non-invasive testing 1

Risk Stratification

Duke Treadmill Score

• Calculate as: Exercise time - (5 × ST deviation in mm) - (4 × angina index)
• Risk categories:
  • Low risk: Score ≥5 (annual mortality <1%)
  • Moderate risk: Score between -10 and +4
  • High risk: Score ≤-10 (annual mortality >5%) 2

Common Pitfalls and Caveats

1. Gender differences: Interpretation of chest pain is particularly difficult in young and middle-aged women. The classical symptom complex of chronic stable angina is less reliable in women than in men due to higher prevalence of coronary artery spasm and 'Syndrome X' 1

2. Unnecessary testing: Avoid routine echocardiography or radionuclide imaging for assessment of left ventricular function in patients with normal ECG, no history of MI, and no evidence of heart failure 1

3. Follow-up testing: Repeated stress testing is not recommended within 3 years for patients with no change in clinical status and low risk on initial evaluation 1

4. Elderly patients: Despite concerns about polypharmacy and drug interactions, elderly patients should receive the same diagnostic workup as younger patients when stable angina is suspected 1

5. Differential diagnosis: Always consider non-cardiac causes of chest pain, especially when symptoms are atypical 1

By following this systematic approach to diagnosis, clinicians can effectively identify patients with stable angina, stratify their risk for future cardiac events, and guide appropriate treatment decisions to improve both symptoms and prognosis.