ACS - Stress Testing

Background

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

ECG-Based Exercise Treadmill Testing

• 68% sn, 77% sp
• Contraindications to Exercise Testing
  • Absolute
    • MI (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 HTN (>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 EKG changes

Echocardiography

• Sn 80% sp 84%
  • When used in low-risk pts, NPV 97-100%

• Who should be tested (ACC/AHA Class IIa)
  
  • patients with abnormal baseline EKG
  • 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!

Nuclear Medicine aka PMIBI

• Who Should be Tested
  • patients with intermediate risk ACS who have uninterpretable EKGs or are unable to exercise
  • patients in whom stress echocardiography is unlikely to yield a technically adequate study

• Who Shouldn’t be
  • Low risk patients

• The Bottom Line
  • P-MIBI has greater sensitivity than stress echo in the diagnosis of CAD (not what we’re interested in) at much higher cost and technical difficulty
  • Both studies have good sensitivity and specificity for the diagnosis of ACS and good NPV for short-term events (what we’re interested in)

See Also

Acute Coronary Syndrome (Main)

Source

Tintinalli