When is a stress test indicated?

Indications for Stress Testing

Stress testing is indicated for patients with suspected coronary artery disease (CAD), patients with known CAD who have new or worsening symptoms, and for risk stratification in specific clinical scenarios. 1

Primary Indications

Diagnostic Evaluation

• Evaluation of patients with intermediate pre-test probability of CAD who present with chest pain or angina-equivalent symptoms 2, 1
• Assessment of patients with low-risk acute chest pain after negative initial cardiac biomarkers and ECG 2
• Evaluation of patients with known non-obstructive CAD (<50% stenosis) who develop new symptoms 2

Risk Stratification

• Prognostic assessment after myocardial infarction (MI) 2
• Evaluation of functional capacity in patients with known cardiovascular disease 1
• Assessment of patients with valvular heart disease, particularly aortic stenosis with mean gradient >30 mmHg or peak gradient >50 mmHg 1
• Evaluation of patients with hypertrophic cardiomyopathy to detect dynamic left ventricular outflow tract obstruction 1

Special Populations

• Evaluation of asymptomatic persons with diabetes mellitus who plan to start vigorous exercise 2, 1
• Assessment of patients with arrhythmias to evaluate effectiveness of antiarrhythmic therapy 1

Specific Clinical Scenarios

Post-MI Assessment

• Before discharge (submaximal at 4-6 days post-MI) for prognostic assessment and activity prescription 2
• Early after discharge (symptom-limited at 14-21 days) if predischarge test was not done 2
• Late after discharge (symptom-limited at 3-6 weeks) if early test was submaximal 2

Emergency Department Evaluation

• For low-risk chest pain patients in observation units after ruling out acute MI 2
• For intermediate-risk patients with suspected acute coronary syndrome who have been clinically stable for 8-12 hours 2, 1

Contraindications

Absolute Contraindications

• Acute myocardial infarction within 2 days 1
• Unstable angina not previously stabilized 1
• Uncontrolled cardiac arrhythmias causing symptoms or hemodynamic compromise 1
• Symptomatic severe aortic stenosis 1
• Uncontrolled symptomatic heart failure 1
• Acute pulmonary embolism, myocarditis, or pericarditis 1

Relative Contraindications

• Left main coronary stenosis 2
• Moderate to severe aortic stenosis without symptoms 1
• Hypertrophic cardiomyopathy with severe resting gradient 1
• Significant electrolyte abnormalities 1

Limitations and Alternative Testing

ECG Limitations

• Standard exercise ECG testing is not diagnostic in patients with:
  • Left bundle branch block
  • Paced ventricular rhythm
  • Wolff-Parkinson-White syndrome
  • Significant resting ECG abnormalities
  • Digoxin therapy

  • 1 mm of resting ST-segment depression 2, 1

Alternative Testing Modalities

• Stress echocardiography or nuclear perfusion imaging should be used when:
  • Baseline ECG abnormalities limit interpretation 1, 3
  • Patient is unable to exercise adequately 1
  • Higher sensitivity or specificity is needed 3

Common Pitfalls

1. Inappropriate testing in low-risk populations: Exercise stress testing has limited value in adults under 40 years with suspected intermediate risk of acute coronary syndrome (0.4% incidence of positive tests) 4

2. Overreliance on test results: A positive stress test increases pre-test probability by only 6-20%, while a negative test decreases it by only 2-28% 5

3. Ignoring pre-test probability: The diagnostic accuracy of stress testing is significantly influenced by the prevalence of coronary artery disease in the population being tested 5

4. Unnecessary testing: Stress testing is not indicated for:

   • Asymptomatic patients with normal resting ECG and preserved e' velocity 2
   • Patients with abnormal findings at baseline consistent with elevated LV filling pressures 2
   • Patients who can achieve 4 metabolic equivalents without symptoms before non-cardiac surgery 6
   • Patients with known CAD who have no new symptoms less than 2 years after PCI or less than 5 years after CABG 6

5. Failure to select the optimal test: MIBI-SPECT offers the greatest sensitivity (87%) while stress echocardiography provides the greatest specificity (88-94%) 3

By following these evidence-based indications and avoiding common pitfalls, clinicians can appropriately utilize stress testing to diagnose coronary artery disease, stratify risk, and guide management decisions for patients with suspected or known cardiovascular disease.