Stress Myocardial Perfusion Imaging

1. See Also
   1. Exercise Stress Test
   2. Stress Imaging
   3. Pharmacologic Stress Test
   4. Stress Echocardiogram
2. Background
   1. Thallium 201 was originally used for imaging
   2. Technetium agents replaced Thallium for higher efficacy
3. 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. Advantages of Stress Thallium
   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
5. Efficacy
   1. Overall SPECT: 87% Sensitive, 73% Specific
   2. Pharmacologic: 89% Sensitive, 75% Specific
   3. Symptomatic: >85% Sensitive, >80% Specific
6. 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