myocardial perfusion & viability scintigraphy
- ECG stress testing for patients with suspected coronary artery disease
- triage in patients presenting to the emergency room with chest pain & ECG without evidence of acute myocardial ischemia (non-ST segment elevation myocardial infarction, NSTEMI)
- baseline second degree heart block is a contraindication to use of adenosine
- contraindications to pharmaceutical vasodilators
- contraindications to use of dobutamine include
- relevant issue is whether coronary anatomy is amenable to revascularization
- false positive results may be obtained in patients with left bundle branch block & severe left ventricular hypertrophy
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.
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.
|resting image||stress image||interpretation|
|normal||perfusion defect||stress-induced ischemia|
|perfusion defect||perfusion defect||myocardial infarct|
- adenosine or dipyridamole may cause chest pain, dyspnea or flushing
- radiation exposure
- patient dissatisfaction
More general terms
More specific terms
- The Guide to Cardiology, 3rd edition, RA Kloner (editor), LeJacq communications, Greenwich Connecticut, 1995
- Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 86
- 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
- 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
- Medical Knowledge Self Assessment Program (MKSAP) 15, 17, 19. American College of Physicians, Philadelphia 2009, 2015, 2022
- 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
- Geriatric Review Syllabus, 11th edition (GRS11) Harper GM, Lyons WL, Potter JF (eds) American Geriatrics Society, 2022
- Veterans Administration