When are exercise stress tests recommended for patients with suspected coronary artery disease?

Exercise Stress Tests for Suspected Coronary Artery Disease

Exercise stress tests are recommended as the initial diagnostic test for patients with intermediate pretest probability of coronary artery disease who can exercise and have a normal resting ECG. 1

Patient Selection for Exercise Stress Testing

• Exercise ECG testing should be the first-line test for patients with suspected coronary artery disease who:

  • Have an intermediate pretest probability of CAD (15-65%) 1
  • Are capable of exercising 1
  • Have a normal resting ECG without ST abnormalities that would interfere with interpretation 1
  • Are not taking medications that would affect ECG interpretation (e.g., digoxin) 1

• Exercise stress testing is contraindicated in patients with:

  • Severe comorbidities limiting life expectancy 1
  • Uncompensated heart failure 1
  • Significant arrhythmias 1
  • ECG abnormalities that interfere with interpretation:
    • Left bundle branch block 1
    • Pre-excitation (Wolff-Parkinson-White) syndrome 1
    • Electronically paced ventricular rhythm 1

    • 1mm ST depression at rest 1

Alternative Testing Modalities

• Stress testing with imaging (echocardiography or nuclear perfusion) is recommended when:

  • Patients have resting ECG abnormalities that prevent accurate interpretation 1
  • Patients are unable to exercise adequately 1
  • Patients have a high pretest probability (66-85%) of CAD 1
  • Left ventricular function assessment is needed (LVEF <50%) 1
  • Patients have had previous revascularization (PCI or CABG) 1

• Pharmacological stress testing with imaging is recommended for patients who cannot exercise due to physical limitations 1

Prognostic Value and Risk Stratification

• Exercise ECG provides important prognostic information beyond diagnosis, including:

  • Exercise capacity/duration 1
  • Heart rate and blood pressure response 1
  • Symptom development during testing 1
  • ST-segment changes 1

• The Duke Treadmill Score is the most validated tool for risk stratification and should be calculated when using the Bruce protocol 1:

  • Score = Exercise time (minutes) - (5 × ST deviation in mm) - (4 × angina index)
  • Low risk (score ≥5): 4-year survival rate of 99% (annual mortality 0.25%) 1
  • Intermediate risk (score -10 to +4): Moderate annual mortality 1
  • High risk (score ≤-10): 4-year survival rate of 79% (annual mortality 5%) 1

• A negative exercise test in patients with low pretest probability has excellent negative predictive value (cardiac death/MI <1% per year) 1

Special Populations

• Women:

  • Exercise ECG has lower specificity in women but remains a reasonable initial test 1
  • A randomized trial showed no incremental benefit of nuclear imaging over standard exercise testing in symptomatic women with preserved functional capacity 1

• Athletes:

  • Exercise stress testing is pivotal for evaluating athletes with suspected CAD who wish to participate in competitive sports 1
  • If the maximal exercise test is normal and cardiovascular risk factor profile is low, no restrictions for competitive sports are advised 1

• Asymptomatic patients:

  • Routine screening with exercise testing is generally not recommended in asymptomatic individuals 2
  • May be considered in asymptomatic persons with diabetes who plan to start vigorous exercise 1
  • May be considered in asymptomatic men >45 years and women >55 years who plan to start vigorous exercise, especially if previously sedentary 1

Diagnostic Accuracy

• The diagnostic accuracy of exercise stress testing varies based on:

  • Patient age and gender 3
  • Prevalence of CAD in the tested population 3
  • Test modality used 3

• Exercise echocardiography has better diagnostic performance than exercise ECG:

  • Higher positive likelihood ratio (7.94 vs 3.57) 3
  • Better negative likelihood ratio (0.19 vs 0.38) 3

• Exercise testing is more useful for excluding CAD than confirming it 3, 4

Common Pitfalls and Caveats

• False positive results are more common in:

  • Women 1
  • Patients with LV hypertrophy 1
  • Patients with electrolyte imbalances 1
  • Patients with intraventricular conduction abnormalities 1
  • Patients with atrial fibrillation 1

• Submaximal testing (not reaching target heart rate) reduces sensitivity 1

• Referral for pharmacological rather than exercise stress testing is independently associated with higher mortality (HR 2.7), likely reflecting underlying comorbidities 5

• Exercise stress testing should only be performed in emergency department chest pain patients as part of a carefully constructed protocol after screening for high-risk features 1