What is the algorithm for evaluating stable angina?

Algorithm for Evaluating Stable Angina

The evaluation of stable angina should follow a systematic approach starting with clinical assessment, followed by appropriate diagnostic testing, risk stratification, and management decisions based on the results. 1

Step 1: Initial Clinical Assessment

• Chest Pain Characterization:

  • Assess the three key features of angina 1:
    1. Substernal chest discomfort of characteristic quality and duration
    2. Provocation by exertion or emotional stress
    3. Relief by rest and/or nitroglycerin within minutes
  • Classify as: typical angina (all 3 features), atypical angina (2 features), or non-cardiac chest pain (0-1 features)

• Risk Factor Assessment:

  • Document cardiovascular risk factors: age, sex, smoking, diabetes, hypertension, hyperlipidemia, family history of premature CAD
  • Identify comorbidities that may precipitate "functional" angina: anemia, hyperthyroidism, aortic stenosis, uncontrolled hypertension 1

• Physical Examination:

  • Focus on cardiovascular system, signs of heart failure, valvular disease
  • Assess for non-cardiac causes of chest pain

• Resting 12-lead ECG:

  • Mandatory for all patients with suspected angina 1
  • Look for evidence of prior MI, LVH, ST-T wave changes, arrhythmias, conduction abnormalities

Step 2: Pre-test Probability Assessment

• Estimate probability of CAD based on age, sex, and chest pain characteristics 1
  • Low probability: <10-20%
  • Intermediate probability: 20-80%
  • High probability: >80-90%

Step 3: Initial Non-invasive Testing

• For patients with intermediate pre-test probability who can exercise with interpretable ECG:

  • Standard exercise ECG using Bruce protocol and Duke treadmill score 1
  • Duke treadmill score = exercise time (min) - (5 × ST deviation in mm) - (4 × angina index)
    • Low risk: score ≥5 (annual mortality 0.25%)
    • Moderate risk: score between -10 and +4
    • High risk: score ≤-10 (annual mortality 5%)

• For patients with uninterpretable ECG, digoxin use, or unable to exercise:

  • Exercise stress with imaging (echocardiography or nuclear perfusion) if able to exercise 1
  • Pharmacologic stress imaging (dipyridamole, adenosine, or dobutamine) if unable to exercise 1

• For patients with low pre-test probability:

  • Consider no further testing or shared decision-making regarding further evaluation 1

• Contraindications to standard exercise ECG: 1

  • Preexcitation (WPW) syndrome
  • Electronically paced ventricular rhythm

  • 1 mm ST depression at rest

  • Complete left bundle branch block

Step 4: Assessment of Left Ventricular Function

• Echocardiography or radionuclide angiography is indicated for: 1
  • History of MI or Q waves on ECG
  • Symptoms or signs of heart failure
  • Complex ventricular arrhythmias
  • Abnormal cardiac examination suggesting valvular disease or hypertrophic cardiomyopathy

Step 5: Risk Stratification

• Low Risk:

  • Annual cardiovascular mortality <1%
  • Low-risk Duke treadmill score
  • Normal LV function and normal/minimal coronary disease

• Intermediate Risk:

  • Annual cardiovascular mortality 1-2%
  • Moderate-risk Duke treadmill score
  • Moderate ischemia on stress imaging

• High Risk:

  • Annual cardiovascular mortality >2%
  • High-risk Duke treadmill score
  • Severe ischemia on stress imaging
  • Reduced LV ejection fraction
  • High-risk coronary anatomy

Step 6: Coronary Angiography

• Indications for coronary angiography: 1
  • High-risk findings on non-invasive testing
  • Severe or progressive angina despite medical therapy
  • Angina with heart failure symptoms
  • Survivors of sudden cardiac death
  • Inconclusive non-invasive tests with high clinical suspicion

Step 7: Management Decisions

• Medical therapy for all patients:

  • Antianginal medications (nitrates, beta-blockers, calcium channel blockers) 2, 3, 4
  • Antiplatelet therapy (aspirin)
  • Statins and other lipid-lowering therapy
  • ACE inhibitors (particularly with diabetes, hypertension, or LV dysfunction)
  • Risk factor modification (smoking cessation, diet, exercise, diabetes control)

• Consider revascularization for:

  • Persistent symptoms despite optimal medical therapy
  • High-risk coronary anatomy (left main disease, severe three-vessel disease)
  • Significant LV dysfunction with viable myocardium

Common Pitfalls to Avoid

1. Misclassification of chest pain - Non-cardiac chest pain may be incorrectly labeled as angina and vice versa. Use the three cardinal features to classify properly.

2. Overreliance on exercise ECG alone in patients with abnormal baseline ECG or those unable to exercise adequately.

3. Failure to assess LV function in patients with prior MI or heart failure symptoms, which is crucial for prognosis and management decisions.

4. Premature invasive testing without appropriate non-invasive risk stratification in low-risk patients.

5. Neglecting women and elderly patients who may present with atypical symptoms but still have significant CAD.

6. Overlooking comorbidities that may exacerbate angina (anemia, thyroid disease, uncontrolled hypertension).

7. Focusing only on symptom relief without addressing risk factor modification and preventive therapies to reduce mortality and morbidity.