When is stress testing performed after a myocardial infarction (MI)?

Stress Testing After Myocardial Infarction

Noninvasive stress testing should be performed before discharge in patients with STEMI who have not undergone coronary angiography and do not have high-risk clinical features that would warrant coronary angiography. 1

Timing of Stress Testing

The timing of stress testing after MI depends on several clinical factors:

1. Before hospital discharge:

   • Patients who have not undergone coronary angiography and might be potential candidates for revascularization 1, 2
   • Patients without complications who have no high-risk features 1

2. 2-3 weeks after discharge:

   • Patients who had successful primary PCI of the infarct artery with an uncomplicated course 1, 2
   • This timing enables more optimal assessment of functional capacity 1

3. 3-6 weeks after discharge:

   • Clinically stable patients who have undergone successful PCI 2
   • Traditionally, exercise testing was performed within this timeframe 2

4. ≥40 days after discharge:

   • Reassessment of left ventricular ejection fraction (LVEF) in patients with initially reduced LVEF who are candidates for ICD therapy 1

Patient Selection and Test Modality

Exercise Stress Testing

• Appropriate for patients who:
  • Have undergone in-hospital cardiac rehabilitation including low-level exercise
  • Have no symptoms of angina or heart failure
  • Have a stable baseline ECG 48-72 hours before the test 1

Pharmacologic Stress Testing

• Indicated for patients who:
  • Cannot perform adequate exercise 2
  • Have abnormal resting ECG that would interfere with interpretation 2
  • Have physical limitations preventing adequate exercise 2

Types of Exercise Protocols

Two different protocols have been used for early post-MI exercise testing:

1. Traditional submaximal exercise test:

   • Performed at 3-5 days in patients without complications
   • Stops at a prespecified target heart rate or metabolic equivalent level 1

2. Symptom-limited exercise test:

   • Performed at day 5 or later
   • Continues until symptoms develop rather than stopping at a predetermined level 1
   • Provides a significantly greater cardiovascular stress and detects ischemic responses nearly twice as frequently as submaximal testing 3

Clinical Considerations and Caveats

• Safety: Low-level exercise testing appears safe when performed under appropriate conditions, though limited data exist on the safety of early symptom-limited testing 1

• Prognostic value: Exercise findings that identify higher risk include:

  • 1 mm ST segment depression from rest level

  • Angina during exercise
  • Decrease in systolic blood pressure with increasing work
  • Presence of complex ventricular arrhythmias
  • Exercise tolerance <4 METs 4

• Common pitfall: Waiting too long for stress testing in patients who have not undergone coronary angiography and might benefit from revascularization 1

• Important caveat: For patients with noninfarct artery disease who have undergone successful PCI of the infarct artery and have an uncomplicated course, it is reasonable to discharge with plans for stress imaging within 3-6 weeks rather than performing predischarge testing 1

• LVEF assessment: LVEF should be measured in all STEMI patients, as it is one of the strongest predictors of survival 1