Cardiac Imaging

1. See Also
   1. Acute Coronary Syndrome
   2. Exercise Stress Test
   3. Pharmacologic Stress Test
   4. Stress Echocardiogram
   5. Stress Myocardial Perfusion Imaging
   6. Cardiac Stress Imaging Indications
2. Preparation: Stress Testing
   1. Hold all Beta Blockers 24 hours before test
   2. Hold nitrates (Nitroglycerin) on day of the test
3. Efficacy
   1. Exercise Stress Test
      1. Test Sensitivity: 55-68%
      2. Test Specificity: 70-77%
   2. Stress Echocardiogram
      1. Test Sensitivity: 79-90%
      2. Test Specificity: 80-87%
   3. Stress Myocardial Perfusion Scan (Thallium Scan, SPECT)
      1. Test Sensitivity: 85-90%
      2. Test Specificity: 80-90%
   4. Cardiac CT
      1. Test Sensitivity: 93-97%
      2. Test Specificity: 80-90%
   5. Cardiac Catheterization
      1. Test Sensitivity: 98%
      2. Test Specificity: 82%
   6. References
      1. Garner (2017) Am Fam Physician 96(5): 293-9 [PubMed]
      2. Metz (2007) J Am Coll Cardiol 49(2): 227-37 [PubMed]
      3. Mark (1991) N Engl J Med 325(12): 849-53 [PubMed]
4. Tests: Screening
   1. Indications
      1. Intermediate CAD risk asymptomatic patients
   2. Tests
      1. CT Coronary Calcium
      2. Consider other markers of subclinical disease
         1. Ankle-Brachial Index
         2. Carotid intimal-medial thickness
         3. Retinography
5. Tests: Stress Test
   1. Indications
      1. Symptomatic patients with intermediate CAD risk
      2. Asymptomatic patients with high CAD risk
   2. Tests:
      1. Exercise Stress Test (no imaging)
         1. Indicated as cost effective first-line test
         2. See Cardiac Stress Imaging Indications
         3. Consider imaging if nondiagnostic EKG is likely (uninterpretable EKG)
            1. Resting ST depression >1mm
            2. Left Bundle Branch Block
            3. Paced rhythm
            4. Digoxin
            5. WPW Syndrome
         4. Avoid non-imaging stress test if prior coronary revascularization (low sensitivity)
      2. Stress Tests with Imaging and Exercise as stressor
         1. Indications
            1. See Cardiac Stress Imaging Indications
         2. Stress Echocardiogram
            1. Most cost-effective, versatile Cardiac Imaging
            2. Large body habitus interferes with echo windows
               1. Consider Optison contrast to increase accuracy
            3. May be better study post-revascularization
               1. Lower sensitivity than Myocardial Perfusion Imaging, but much better Specificity
               2. Stress Echo is less likely to result in False Positive tests post-revascularization
         3. Stress Myocardial Perfusion Imaging
            1. Diaphragm and Breast interferes with images
      3. Stress Imaging with Pharmacologic Provocation
         1. Indicated if patient unable to Exercise 5 mets (~5 minutes on bruce protocol)
         2. Dobutamine Echocardiogram
            1. No Beta Blockers for 24 hours before test
         3. Myocardial Perfusion Imaging with Adenosine
            1. Avoid in severe COPD, Asthma, Carotid Stenosis
            2. No nitrates on day of test
            3. No Methylxanthines (e.g. Caffeine) for 24 hours
         4. Myocardial Perfusion Imaging with Dipyridamole
6. Tests: Angiography
   1. Indications
      1. Significantly abnormal stress test (see above)
      2. Symptomatic patient and high Cardiac Risk
   2. Tests
      1. See Coronary Angiography
      2. CT Coronary Angiography
      3. MR Coronary Angiography
7. Tests: Adjunctive
   1. Transthoracic Echocardiogram
      1. See Echocardiogram in Myocardial Infarction
   2. Transesophageal Echocardiogram
      1. Evaluates for non-ischemic intracardiac lesions
      2. Aortic Dissection
      3. Valvular dysfunction (including vegetations)
      4. Intracardiac thrombi
      5. Intracardiac shunts
8. References
   1. Garner (2017) Am Fam Physician 96(5): 293-9 [PubMed]
   2. Mieres (2007) Am Fam Physician 75:1219-28 [PubMed]
   3. Shaw (2006) J Am Coll Cardiol 47:S15 [PubMed]