Prognostic value of cardiac imaging in patients with known or suspected coronary artery disease: Comparison of myocardial perfusion imaging, stress echocardiography, and positron emission tomography

Abstract

Prior studies have suggested that, compared with angiographic, exercise electrocardiographic, and clinical data in patients with known or suspected coronary artery disease (CAD), the data provided by exercise thallium-201 scintigraphy are the best predictor of cardiac events. The most consistent finding is that the presence and extent of jeopardized viable myocardium, manifest by transient thallium-201 defects, predicts cardiac events. In addition, a normal thallium-201 scan reliably predicts an annual event rate for cardiac death or nonfatal myocardial infarction of < 1% per year, a rate approaching that of a normal aged-matched population. Further, it has been demonstrated that the incremental prognostic value of transient thallium-201 defects is statistically significant and nearly double that of clinical data and stress electrocardiography combined, and, importantly, not significantly different from that obtained by adding angiographic data. These results appear to hold for the newer, technetium-99m-based perfusion agents such as sestamibi, for which sensitivity and specificity for detecting CAD are comparable. Stress echocardiography, which depends on development of a secondary phenomenon (abnormal wall motion), appears to be less sensitive for the detection of CAD than myocardial perfusion imaging (which can detect the primary insult, hypoperfusion); stress echocardiography is also less sensitive for detection of jeopardized viable myocardium. Because of its lower sensitivity for detecting jeopardized viable myocardium, stress echocardiography may underestimate the risk of cardiac events, especially in patients with known CAD. Thus it may not reliably identify a low-risk group, especially in patients with known CAD. A final modality, positron emission tomography (PEp, with its high sensitivity for CAD and ability to distinguish viable from nonviable myocardium, may be an important predictor of cardiac events, although additional data are required to evaluate this potential. Prior studies have suggested that, compared with angiographic, exercise electrocardiographic, and clinical data in patients with known or suspected coronary artery disease (CAD), the data provided by exercise thallium-201 scintigraphy are the best predictor of cardiac events. The most consistent finding is that the presence and extent of jeopardized viable myocardium, manifest by transient thallium-201 defects, predicts cardiac events. In addition, a normal thallium-201 scan reliably predicts an annual event rate for cardiac death or nonfatal myocardial infarction of < 1% per year, a rate approaching that of a normal aged-matched population. Further, it has been demonstrated that the incremental prognostic value of transient thallium-201 defects is statistically significant and nearly double that of clinical data and stress electrocardiography combined, and, importantly, not significantly different from that obtained by adding angiographic data. These results appear to hold for the newer, technetium-99m-based perfusion agents such as sestamibi, for which sensitivity and specificity for detecting CAD are comparable. Stress echocardiography, which depends on development of a secondary phenomenon (abnormal wall motion), appears to be less sensitive for the detection of CAD than myocardial perfusion imaging (which can detect the primary insult, hypoperfusion); stress echocardiography is also less sensitive for detection of jeopardized viable myocardium. Because of its lower sensitivity for detecting jeopardized viable myocardium, stress echocardiography may underestimate the risk of cardiac events, especially in patients with known CAD. Thus it may not reliably identify a low-risk group, especially in patients with known CAD. A final modality, positron emission tomography (PEp, with its high sensitivity for CAD and ability to distinguish viable from nonviable myocardium, may be an important predictor of cardiac events, although additional data are required to evaluate this potential.