ACS - Stress Testing

Background

  • Stress testing is recommended for patients with low-moderate pretest probability of CAD
    • Not helpful in patients with very low risk or high risk

ECG-Based Exercise Treadmill Testing

  • 68% sn, 77% sp[1]
  • Contraindications to Exercise Testing
    • Absolute
      • Myocardial infarction (within 2 days)
      • High-risk unstable angina
      • Uncontrolled cardiac dysrhythmias
      • Symptomaticaortic stenosis
      • Uncontrolled symptomatic heart failure
      • Acute pulmonary embolus or pulmonary infarction
      • Acute myocarditis or pericarditis
      • Acute aortic dissection
    • Relative
      • Baseline ST segment abnormalities
      • Left main coronary stenosis
      • Moderate stenotic valvular heart disease
      • Electrolyte abnormalities
      • Severe hypertension (>200 sys, >110 dia)
      • Tachydysrhythmias or bradydysrhythmias
      • HOCM
      • Mental or physical impairment
      • High-degree atrioventricular block


  • The Bottom Line:
    • ETT has low sensitivity and specificity overall (especially for women) and as such is not a good test for patients in whom suspicion for ACS is high
    • ETT is safe in low-risk and select intermediate-risk patients as a way of determining who is at low risk for short term adverse events (and therefore can go home)
    • ETT does not have prognostic value for patients who return to the ED with concerning symptoms or ECG changes

Stress Echocardiography

  • Sn 80% sp 84%
    • When used in low-risk patients, NPV 97-100%
  • Who should be tested (ACC/AHA Class IIa)
    • patients with abnormal baseline ECG
    • patients unable to exercise
    • women with low- to intermediate-risk
  • Who shouldn’t be tested with stress echo
    • patients in whom a sub-optimal study is likely (very obese, COPD with expanded AP chest diameter, etc)
    • patients with grossly abnormal baseline LV or valvular function (e.g. severe AS)


  • The Bottom Line
    • Stress echocardiography (chemical or exercise induced) has greater sensitivity and specificity than ETT for ACS (especially for women)
    • Patients with normal stress echos are at very low risk for mortality within 1 year
    • A normal stress echo does not preclude subsequent ACS, nor should it lower suspicion for ACS when a patient presents with new symptoms!


Cardiac Radionuclide Imaging

Nuclear myocardial perfusion imaging is generally appropriate in patients with acute chest pain in which the diagnosis of acute coronary syndrome is unclear, to determine whether or not cardiac catheterization is indicated, or to determine prognosis. Appropriate Use Criteria (AUC) has been developed by the American College of Cardiology and is updated regularly. [2]. Absolute contraindications to stress testing include acute myocardial infarction (within 2 days), unstable angina, and symptomatic heart failure. [3]. The decision to perform nuclear myocardial perfusion imaging or stress echo imaging generally depends upon local expertise. The benefit of nuclear imaging is that it can be performed in nearly 100% of patients, whereas echo stress testing is more limited by body habitus and the ability to obtain good imaging windows quickly after stressing the patient. The benefit of echo stress testing is lower costs and no radiation exposure. The amount of radiation exposure from a stress-rest nuclear myocardial perfusion scan is typically 10 mSv or less for gamma camera based imaging (similar to a chest CT), and under 5 mSv for PET imaging.


  • PATIENTS WITH ACUTE CHEST PAIN: APPROPRIATE INDICATIONS
    • Patients with acute chest pain with possible acute coronary syndrome: a) ECG shows no ischemic changes, LBBB, or electronically ventricular paced rhythm; and b) negative to borderline elevated troponin levels.
    • In this setting, nuclear imaging is considered appropriate in both low-risk TIMI score and high-risk TIMI score patients
  • PATIENTS WITH ACUTE CHEST PAIN: INAPPROPRIATE INDICATIONS
    • Patients with definite acute coronary syndrome
    • Early stress testing contraindicated within 2 days after myocardial infarction
  • THE BOTTOM LINE
    • Asymptomatic patients in need of risk stratification typically will undergo exercise ECG testing only. Imaging is indicated only when the ECG is uninterpretable, the patient is unable to adequately exercise, or the pretest probability is intermediate or high.
    • Symptomatic patients with an uncertain diagnosis of acute coronary syndrome frequently undergo a stress imaging procedure first, then depending upon the result, may or may not undergo cardiac catheterization.
    • The decision regarding stress nuclear versus stress echo is usually made based upon availability of local expertise.

See Also

References

  1. Gianrossi R, Detrano R, Mulvihill D, Lehmann K, Dubach P, Colombo A, McArthur D, Froelicher V. Exercise-induced ST depression in the diagnosis of coronary artery disease. A meta-analysis. Circulation. 1989 Jul;80(1):87-98.
  2. Hendel RC, Berman DS, Di Carli MF et al. ACCF/ASNC/ACR/AHA/ASE/SCCT/SCMR/SNM 2009 Appropriate Use Criteria for Cardiac Radionuclide Imaging: A Report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, the American Society of Nuclear Cardiology, the American College of Radiology, the American Heart Association, the American Society of Echocardiography, the Society of Cardiovascular Computed Tomography, the Society for Cardiovascular Magnetic Resonance, and the Society of Nuclear Medicine. J Am Coll Cardiol. 2009 Jun 9;53(23):2201-29.
  3. Gibbons RJ, Balady GJ, Beasley JW et al. ACC/AHA guidelines for exercise testing: executive summary. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Exercise Testing). Circulation. 1997 Jul 1;96(1):345-54.