Myocardial Perfusion Imaging for Risk Stratification in Suspected or Known Coronary Artery Disease: Current Status and L
Coronary artery disease (CAD) remains the leading cause of morbidity and mortality in the western world. Early detection and risk stratification of underlying (CHD) is a major step in clinical decision-making. As discussed in the other chapters, myocardia
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Myocardial Perfusion Imaging for Risk Stratification in Suspected or Known Coronary Artery Disease: Current Status and Limitations
20
Firas A. Ghanem and Assad Movahed
20.1
Contents
20.1 20.2 20.3 20.4 20.5 20.6 20.7
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . Chronic Stable Angina . . . . . . . . . . . . . . . . . Acute Coronary Syndrome (ACS) . . . . . . . . Asymptomatic Patients . . . . . . . . . . . . . . . . . MPI in Women . . . . . . . . . . . . . . . . . . . . . . . Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction
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Coronary artery disease (CAD) remains the leading cause of morbidity and mortality in the western world. Early detection and risk stratification of underlying (CHD) is a major step in clinical decision-making. As discussed in the other chapters, myocardial perfusion imaging (MPI) using thallium-201(Tl-201) or technetium-99m (Tc-99m) sestamibi or tetrofosmin, is used in various clinical settings to provide invaluable information on myocardial perfusion, left ventricular volumes and left ventricular function, and prognosis. MPI has the ability to localize hemodynamically important coronary stenosis; thus yielding positive results by increasing demand myocardial ischemia during exercise or inducing inhomogeneous distribution of radiotracers during pharmacological stress testing with dipyridamole or adenosine [1]. 20.2
Chronic Stable Angina
Significant CAD is defined angiographically as CAD with greater than or equal to 70% diameter stenosis of at least one major epicardial artery segment or greater than or equal to 50% diameter stenosis of the left main coronary artery. Although lesions of less stenosis can cause angina, they have much less prognostic significance [2]. For patients with chronic chest pain syndromes, testing is directed towards establishing the presence or absence of CAD to guide therapy and determine prognosis. Special consideration needs to be given to establishing the pre-test probability of CAD based on the patient’s history, physical examination and risk factor assessment [3]. Those with an intermediate to high pre-test probability of CAD are considered the best candidates for sin-
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Firas A Ghanem and Assad Movahed
gle-photon emission computed tomography myocardial perfusion imaging (SPECT MPI) whereas it is deemed inappropriate for patients with low pre-test probability [4]. The referral bias can influence the sensitivity and specificity of MPI. While most patients with an abnormal scan undergo coronary angiography, few patients with a normal MPI are referred for invasive procedures. Referral bias may result in an overestimation of test sensitivity and an underestimation of test specificity. Reported sensitivities (the percentage of abnormal images in patients with significant CAD) of exercise and vasodilator stress SPECT MPI a
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