Stress Myocardial Perfusion Imaging

Aka: Stress Myocardial Perfusion Imaging, Radionuclude Perfusion Imaging, Cardiac Radionuclide Imaging, SPECT Myocardial Perfusion Imaging, Myocardial Single-Photon Emission Computed Tomography, Stress Thallium, Stress Cardiolite, Myocardial Perfusion Imaging, Myocardial Scintigraphy, Radionuclide Myocardial Perfusion Study

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II. Definitions

  1. Single Photon Emission Computed Tomography (SPECT)
    1. Radiolabeled Contrast Material is injected
    2. Emitted radiation from Contrast Material uptake is measured by an external gamma camera
      1. Contrast with CT in which applies x-ray source through a patient to detectors
    3. Other detectors of emitted radiation include scintigraphy and positron emission tomography (PET)
  2. Hybrid CT and SPECT Scanners
    1. CT adds precise anatomic positioning to the SPECT's physiologic data
    2. CT also facilitates correction of attenuation artifacts

III. Preparations

  1. Thallium T1 201 chloride
    1. Originally used for imaging
  2. Technetium agents replaced Thallium for higher efficacy
    1. Technetium 99mTc-Sestamibi (Cardiolite)
    2. Technetium Tc-99m-tetrofosmin (Myoview)

IV. Indications

  1. Nondiagnostic Stress EKG, Intermediate CAD likelihood
    1. Resting ST-T Wave abnormalities
    2. Left Bundle Branch Block
    3. Ventricular paced rhythm
    4. Left Ventricular Hypertrophy
    5. Digoxin treatment
  2. Suspected Acute Coronary Syndrome, nondiagnostic tests
  3. CAD Diagnosis, risk stratification, and therapy
    1. Assess ventricular function
    2. Identify lesions in planning for PTCA intervention
    3. Risk stratification prior to noncardiac surgery
  4. Specific conditions
    1. Cocaine-associated Chest Pain
    2. Well-controlled Diabetes Mellitus

V. Advantages

  1. High sensitivity for ischemia (>90%)
  2. Distinguishes baseline wall motion abnormality from CAD
    1. Severe valvular disease
    2. Severe Hypertension
    3. Idiopathic Hypertrophic Subaortic Stenosis (IHSS)
    4. Left Bundle Branch Block
    5. Severe Left Ventricular Hypertrophy
    6. Atrial Fibrillation
  3. In above cases angiography may be needed

VI. Disadvantages

  1. Test Sensitivity decreases significantly when patient is not actively experiencing Chest Pain

VII. Efficacy: Coronary Ischemia

  1. Overall SPECT
    1. Test Sensitivity: 85-90%
    2. Test Specificity: 80-90%
    3. McArdle (2012) J Am Coll Cardiol 60(18): 1828-37 [PubMed]
  2. Pharmacologic with Dobutamine
    1. Test Sensitivity: 89%
    2. Test Specificity: 75%
    3. Multi-vessel Disease Test Sensitivity: 44%
    4. Geleinjnse (2000) J Am Coll Cardiol 36(7): 2017-27
  3. Symptomatic
    1. Test Sensitivity: >85%
    2. Test Specificity >80%
  4. References
    1. Metz (2007) J Am Coll Cardiol 49(2): 227-37 [PubMed]

VIII. Prognosis

  1. Normal perfusion scan: Cardiac event rate <1% per year
  2. Factors suggestive of worse prognosis
    1. Increased numbers of involved vascular territories
    2. Increased severity and extent of defect size
    3. Decreased reversibility
    4. Post-stress ejection fraction <45%
    5. End-systolic volume >70 ml
    6. Transient ischemic dilation

IX. References

  1. Broder (2022) Crit Dec Emerg Med 36(6): 20-1

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