Seminars in Nuclear Medicine VOL XXIX, NO 4 pdf

Seminars in Nuclear Medicine VOL XXIX, NO OCTOBER 1999 L e t t e r F r o m the E d i t o r s UR GUEST editors have assumed the additional role of guest authors for this issue on the topic of Cardiovascular Nuclear Medicine They have performed equally well, clearly defining the role of pharmacological stress testing in the assessment of cardiovascular disease This alternative to standard treadmill exercise is achieving increased application with the availability of several agents that have significantly different pharmacological actions As Drs Wexler and Travin point out, approximately 60% of patients with suspected cardiovascular disease are stressed pharmacologically at our institution The remaining articles in this issue are equally informative Dr Berman has synthesized his prodigious contributions to the cardiovascular nuclear medicine literature and presents a cogent review of the role of cardiovascular nuclear medicine in clinical decision making This article is essential for anyone who performs or uses these studies The algorithms presented for cardiovascular nuclear medicine are well thought out and critical to our use of these tests Cardiovascular nuclear medicine plays a powerful role in risk stratification, diagnosis, and therapy Another area of concern to many nuclear medicine physicians is the increasing use of stress echocardiography as a potential substitute for thallium and sestamibi studies Dr Verani defines for O Seminars in Nuclear Medicine, Vol XXIX, No (October), 1999: p 279 us the advantages and limitations of stress echocardiography in evaluating myocardial perfusion The introduction of hypoxia markers for myocardial imaging is discussed along with many other exciting developments These agents, as discussed by Dr Sinusas, have the potential to allow us to directly image myocardial tissue, which is hypoxic Thrombosis and atherosclerotic plaques are lifethreatening problems that have obvious implications in the pathogenesis of heart disease Unfortunately, therapy of thrombosis with anticoagulants also is not without risk Dr Cerqueira reviews newly introduced agents for thrombosis imaging and their potential application in clinical nuclear medicine As he notes, "efforts in developing those modalities are important to expand the applications to new areas in nuclear cardiology." Cardiovascular nuclear medicine continues to represent the single, most frequently performed, group of studies in most nuclear medicine departments This and the previous issue of Seminars in Nuclear Medicine provide a comprehensive account of the state-of-the-art techniques in cardiovascular nuclear medicine by internationally recognized authorities Leonard M Freeman, MD M Donald Blaufox, PhD 279 The Role of Nuclear Cardiology in Clinical Decision Making Daniel S, Berman, Guido Germano, and Leslee J, Shaw This review suggests that the field of nuclear cardiology is alive, well, and thriving, providing relevant information that aids in everyday clinical decision making for nuclear medicine and referring physicians alike Despite the competition from other modalities, the clinically appropriate applications of nuclear cardiology techniques are likely to increase The foundation of this optimism is based on the vast amount of data documenting cost-effective clinical applications for diagnosis, risk stratification, and assessing therapy in both chronic and acute coronary artery disease (CAD), the powerful objective quantitative analysis of perfusion and function provided by the technique, and the increasing general availability of the approach MONG THE million myocardial perfusion studies performed in the United States per year, approximately one half are still performed, at least in part, for purposes of simply establishing a diagnosis Detection of coronary artery disease (CAD) remains important in certain patients with high-risk occupations, as well as in younger patients, for whom CAD detection, with its lifelong implications for therapy, may be important regardless of the likelihood of cardiac events over a 1- to 3-year period The basis for the diagnostic application of nuclear testing lies in the concept of sequential Bayesian analysis of disease probability 1This analysis requires knowledge of the pretest likelihood of disease, as well as of the sensitivity and specificity of the test The pretest likelihood of disease or prevalence of disease varies according to age, sex, symptoms, and risk factors, and can be derived directly from the work of Diamond and Forrester,z as well as other data bases One can consider this likelihood, for 50-year-old men, to be 5%, 20%, 50%, and 90% for asymptomatic, nonanginal chest pain, atypical angina, and typical angina, respectively Values are scaled up or down depending on age The likelihood values for women of 5%, 20%, 50%, and 90%, roughly apply just as they with men, but starting decade later It has been shown that all imperfect noninvasive tests have their maximum diagnostic benefit when the pretest likelihood of disease is intermediate, z,3 With well-performed gated myocardial perfusion single photon emission computed tomography (SPECT), we estimate the sensitivity to be 90% and the specificity to be 90% Given the 90% sensitivity and 90% specificity, it can be shown that a positive test result in the context of 50% pretest likelihood results in a 90% likelihood of CAD, and a negative test result in a 10% likelihood of CAD This process can be seen in Figure 1.3 Our clinical algorithm for the purpose of simple detection of CAD is shown in Figure Patients with a low probability (50% stenosis) CAD can be identified, even before the standard exercise tolerance test (ETT) is performed Patients with a low pre-ETT likelihood of CAD not require further diagnostic testing, although continued medical follow-up or a watchful waiting approach is recommended Patients with a low-intermediate pre-ETT likelihood of CAD (0.15 to 0.50) would undergo standard ETT as the next diagnostic step Those who continue to have an intermediate likelihood of CAD after ETT (or those with an indeterminate ETT) and those whose pre-ETT likelihood of CAD was in the 0.50 to 0.85 range (in these patients even a negative ETT would not result in a low likelihood of CAD) will benefit from exercise nuclear testing Patients with a high pre-ETT likelihood of CAD (>0.85) are generally considered to have an established diagnosis of CAD, and nuclear stress testing is not needed for diagnostic purposes Nevertheless, as described below, these noninvasive procedures may be very effective in risk stratification and may aid in consideration of invasive patient management strategies A From the Departments of Medicine and Radiological Sciences, UCLA School of Medicine, the Departments of Nuclear Cardiology and Nuclear Medicine Physics, Cedars-Sinai Medical Center, Los Angeles, CA; and the Department of Medicine and Center for Outcomes Research, Emory University, Atlanta, GA Address reprint requests to Daniel S Berman, MD, Director, Nuclear Cardiology, Cedars-Sinai Medical Center, 8700 Beverly Blvd, AO42N, Los Angeles, CA 90048 Copyright 1999 by W.B Saunders Company 0001-2998/99/2904-0001510.00/0 280 Copyright9 1999by W.B Saunders Company RISK STRATIFICATION AND PATIENT MANAGEMENT The most rapidly growing area of application of nuclear cardiology techniques is risk stratification, Seminars in Nuclear Medicine, Vol XXIX, No (October), 1999: pp 280-297 CLINICAL DECISION MAKING 281 1.0 j // 1I 2 1.0 Pretest Likelihood (Prevalence) Fig Relationship between pretest likelihood (X axis) and posttest likelihood (Y axis) of sngiographically significant CAD for a test with 90% sensitivity and 90% specificity The upper curve (dashed) depicts this relationship for the abnormal test results, and the lower curve (solid) for the normal test results The center line Is the line of Identity Vertical lines a, b, and c delineate three different pretest likelihoods of 0.01, 0.5, and 0.99, respectively The length of these lines can be considered measure of the diagnostic value of the test Note that the longest line (greatest separetlon between the pretest end posttest ilkellhoods) Is assocleted with the mldrange of pretest likelihood (Reprinted with permission, is) and this requires the acceptance of a new paradigm in patient management A risk-based approach to patients with suspected CAD appears better suited to the modem environment of cost containment and dramatic improvements in medical therapy than the approach focusing on simple diagnosis, in which the patient with suspected disease typically undergoes coronary angiography and then frequently is revascularized With the risk-based approach, the I I Low