New Developments in Nuclear Cardiac Imaging

US Cardiology, 2005;2(1):96-102

This article will attempt to cover the areas of historic background, current status, newer applications of existing tracers, attenuation correction, metabolic imaging, sympathetic imaging, new stress agents, molecular imaging, and positron emission tomography (PET) without on-site cyclotron. By no means is it meant to be inclusive of all that is currently happening but rather to illustrate some points of what can be seen as potential and what is needed.

Background

The introduction of the gamma camera in 1965 paved the way in 1973 for the use of Potassium-43 (K-43) for myocardial perfusion imaging, a tracer of only historic interest at present. At almost the same time, thallium-201 came aboard and was the only tracer available for ~15 years because it was not until 1990 that the US Food and Drug Administration (FDA) approved the first technetium-based perfusion tracer. In 1999, gated single positron emission computed tomography (SPECT) imaging was described and soon gained wide acceptance. The FDA approved Adenoscan as a stress agent in 1995. Adenosine, Tc-99m Sestamibi and Tc-99m Tetrofosmin heralded the era of clinical phase 3 trials in nuclear cardiology and in the process paved the way for rapid growth in this field.1 These applications were the subject of two prior presentations in US cardiology by Hendel and by Nobel and Heller.2,3 Alongside the technological advance, the American Society of Nuclear Cardiology (ASNC) was created in 1993 (its official journal was first published in 1994) and the Certification Board of Nuclear Cardiology (CBNC) was established in 1996. There are a large number of educational programs sponsored by the American Heart Association (AHA), American College of Cardiology (ACC), ASNC, and working groups at regional and state levels. The annual program of the ASNC now provides the venue for original research presentations and breaking news from large trials. Despite the emergence of other imaging modalities (echocardiography (ECG), magnetic resonance imaging (MRI) and CT) nuclear cardiology continues to grow and is by far the most widely used method in ischemia work-up. The growth has been in office-based and out-patient facilities, where turf issues are avoided to a large extent. Imaging accounts for almost US$100 billion in health expenditure annually and there is no end in sight in terms of containment. The political ramifications and power struggles are beyond the scope of this presentation although the ACC is hard at work to produce documents that deal with appropriateness and quality, including the uniform requirements for certification and laboratory accreditation.4

References:
  1. Iskandrian A E,Verani M S, Nuclear cardiac imaging: principles and applications 3rd ed., Oxford University press (2003).
  2. Hendel R C,“Practical applications of nuclear cardiology”, US Cardiology (2004).
  3. Noble G L, Heller G V,“Ethic differences in myocardial perfusion imaging. Identifying patients at higher risk”, US cardiology (2004).
  4. Readers interested in this topical debate are encouraged to read the editorial by A N DeMaria in the June 21 2005 issue and the message by P S Douglass in the July 5 2005 issue of the Journal of the American College of Cardiology (JACC).
  5. Shaw L J, Iskandrian A E,“Prognostic Value of Gated Myocardial Perfusion SPECT”, J. Nucl. Cardiol. (2004);11: pp. 171–185.
  6. Chen J T, Garcia E V, Folks R D et al., “Onset of Left Ventricular Mechanical Contraction as Determined by Phase Analysis of ECG-Gated Myocardial Perfusion SPECT Imaging: Development of Diagnostic Tool for Assessment of Cardiac Mechanical Dyssynchrony. J. Nucl. Cardiol. in press.
  7. Barbato E et al., “Role of a-2 Adrenergic Receptors in Human Atherosclerotic Coronary Arteries”, Circulation (2005);111: pp. 288–294.

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