myocardial perfusion & viability scintigraphy

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Indications

prognostic value similar to dobutamine stress echocardiography[4]

prognostic value similar to coronary CT angiography[6]

Contraindications

* exercise cannot be used in patients with LBBB because perfusion defects not related to obstructive coronary artery disease may be seen in the interventricular septum with exercise[5]

* chest pain induced by emotional stress, unrelated to exercise is not an indication for pharmacologic perfusion scintigraphy[5]

Clinical significance

Procedure

caffeine should be withheld 24 hours prior to procedure[5]

single photon emission computed tomography may be method of choice

Perfusion imaging agents include:

A resting image of myocardial uptake of Tl-201 administered in the form of thallous chloride is compared witha post vasodilation uptake of Tc-99 in the form of sestamibi. Vasodilation* may be induced by:

* A 3-5 fold increase in blood flow normally occurs.

# beta-blocker must be held prior to the test

3 mCi of Tl-201 in the form of thallous chloride is administered IV. Cardiac muscle has an extraction efficiency of 80-90% for Tl+. Approximately 4% of administered Tl+ is taken up by the myocardium. Myocardial uptake is dependent upon blood flow. A redistribution occurs reflecting the local K+ pool (i.e. viable myocardium). Redistribution appears to be complete in 3-5 hours. Therefore imaging should be begun within 5 minutes of Tl-201 injection.

Emitted radiation is sensed with an Anger type gamma counter with either medium or high resolution collimators. Images are obtained from the anterior & at least other projections 40 & 70 degrees so that all cardiac segments are well visualized.

Persantine 0.57 mg/kg is injected IV over 4 minutes. At 7 minutes, 25 mCi of Tc-99-labeled sestamibi is injected. Sestamibi is extracted less efficiently than Tl+ & almost no redistribution occurs. This permits a larger time window between isotope injection & imaging for uptake with vasodilation.

With vasodilation, normal arteries vasodilate, but stenotic vessels do not. Nitroglycerin should be avoided as it will dilate stenotic vessels as well.

Resting images may be then compared with images after vasodilation. Three different perpendicular views including short axis, & two long axes views are obtained. A comparison is made of the resting & vasodilation images in order to identify regions of inviable myocardium & regions of myocardium at risk for ischemia during stress.

Interpretation

resting image stress image interpretation
normal normal no ischemia
normal perfusion defect stress-induced ischemia
perfusion defect perfusion defect myocardial infarct
normal LV dilation *

* small or no focal ischemia, possible diffuse ischemia, possible multivessel CAD

Complications

More general terms

More specific terms

Additional terms

References

  1. The Guide to Cardiology, 3rd edition, RA Kloner (editor), LeJacq communications, Greenwich Connecticut, 1995
  2. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 86
  3. Journal Watch 23(3):24, 2003 Udelson JE et al Myocardial perfusion imaging for evaluation and triage of patients with suspected acute cardiac ischemia: a randomized controlled trial. JAMA 288:2693, 2002 PMID: https://www.ncbi.nlm.nih.gov/pubmed/12460092
  4. 4.0 4.1 Journal Watch 24(16):126, 2004
    Schinkel AF et al Long-term prognostic value of dobutamine stress echocardiography compared with myocardial perfusion scanning in patients unable to perform exercise tests. Am J Med. 2004 Jul 1;117(1):1-9. PMID: https://www.ncbi.nlm.nih.gov/pubmed/15210381
    Marwick TH. Does the extent of malperfusion or ischemia on stress testing predict future cardiac events? Am J Med. 2004 Jul 1;117(1):58-9. No abstract available. PMID: https://www.ncbi.nlm.nih.gov/pubmed/15210390
  5. 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 Medical Knowledge Self Assessment Program (MKSAP) 15, 17, 19. American College of Physicians, Philadelphia 2009, 2015, 2022
  6. 6.0 6.1 6.2 6.3 6.4 Levsky JM et al Coronary Computed Tomography Angiography Versus Radionuclide Myocardial Perfusion Imaging in Patients With Chest Pain Admitted to Telemetry: A Randomized, Controlled Trial. Ann Intern Med. Published online 9 June 2015 <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/26052677 <Internet> http://annals.org/article.aspx?articleid=2301406
  7. 7.0 7.1 Geriatric Review Syllabus, 11th edition (GRS11) Harper GM, Lyons WL, Potter JF (eds) American Geriatrics Society, 2022
  8. Veterans Administration