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  • Normal single-photon emission computed tomography (SPECT) or positron emission tomography (PET) myocardial perfusion imaging (MPI) predicts low risk of major adverse cardiac events.

  • Abnormal SPECT or PET MPI predicts multifold increase in risk, commensurate with severity and extent of perfusion abnormalities.

  • SPECT and PET MPI provide incremental prognostic value beyond clinical, stress, and anatomic data.

  • Ancillary SPECT or PET MPI findings, such as left ventricular ejection fraction, left ventricular function reserve, and transient ischemic dilation, further refine risk prediction.

  • PET-derived myocardial blood flow and coronary flow reserve (CFR) measurements provide valuable prognostic information beyond MPI data and can identify residual risk in patients with normal MPI.

  • SPECT and PET MPI and CFR data can guide management decision making.

  • Coronary artery calcium quantification using hybrid SPECT/CT or PET/CT systems further improves risk prediction.

In the past three decades, a great body of literature has established the use of radionuclide myocardial perfusion imaging (MPI) for risk stratification in patients with known or suspected coronary artery disease (CAD). The early studies have been reinforced and enhanced with the use of novel stress agents, modern single-photon emission computed tomography (SPECT) technologies, and positron emission tomography (PET) and with the evolution of the appropriate use criteria (AUC). This chapter will review the use of stress radionuclide SPECT MPI for risk stratification in a general population and among patients with chronic CAD, as well as provide an up-to-date review of the prognostic value of PET perfusion imaging. Risk stratification for specific applications, predominantly focused on SPECT, is discussed elsewhere in this book, including prior to major noncardiac surgery Chapter 21, after therapeutic intervention Chapter 18, in heart failure patients Chapter 22, and for a variety of unique populations Chapter 20.


Risk stratification is of crucial importance for the practice of contemporary medicine. Appropriate management of CAD should include the assessment of the individual risk of future cardiac events, particularly cardiac death and myocardial infarction (MI).1 Extending the paradigm of noninvasive cardiac testing beyond the detection of disease is especially important, as risk assessment permits patient management decisions to be formulated on an evidence-based approach. Patients who are identified as being at a high risk for subsequent cardiac events should be considered for aggressive management, including cardiac catheterization and revascularization procedures that may improve their outcome. Conversely, the management of low-risk patients should be focused toward aggressive medical therapy and risk factor modification,2,3 thus reserving invasive procedures for patients who fail medical management. Additional testing in this low-risk group should generally be avoided, thereby minimizing cost. An outcomes-based risk assessment model strives for improved patient outcomes, avoidance of complications from unnecessary procedures and is cost effective.

Risk strata are often defined in many ways, but when related to CAD events, specifically nonfatal MI and cardiac death, an annual event rate of less than 1% ...

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