Background. Although computed tomography (CT) coronary angiography (CTA) provides detailed assessments of the anatomic extent of coronary artery disease (CAD), its value for predicting myocardial ischemia is unclear. We examined the value of CTA to identify the presence of ischemia, as determined by stress perfusion imaging, using integrated positron emission tomography (PET)-CT imaging.
Methods and Results. We studied 110 consecutive patients (median age, 57 years; 55% male) with suspected CAD undergoing stress rubidium 82 myocardial perfusion PET imaging and CTA in the same setting. Increasing degrees of CTA-detected luminal narrowing (<50%, 50%-70%, and >70%) were associated with reduced sensitivity with commensurate improvements in specificity for identifying myocardial ischemia both on a per-vessel basis and on a per-patient basis. Consequently, with increasing degrees of CTA-detected stenosis severity, the positive predictive value increased (14%, 26%, and 53%, respectively, on a per-vessel basis [P < .001] and 29%, 44%, and 77%, respectively, on a per-patient basis [P โซุโฌ .005]), whereas the negative predictive value was unchanged (97%, 97%, and 96%, respectively, on a per-vessel basis [P โซุโฌ not significant (NS)] and 92%, 91%, and 88%, respectively, on a per-patient basis [P โซุโฌ NS]). Receiver operating characteristic analysis revealed no differences between these 3 anatomic criteria (receiver operating characteristic areas of 0.66 ุ 0.07, 0.73 ุ 0.06, and 0.71 ุ 0.07, respectively [P โซุโฌ NS]) for identifying ischemia. Nearly half of significant angiographic stenoses (47%) occurred without evidence of myocardial ischemia, whereas 50% of normal PET studies were associated with some CTA abnormality.
Conclusions. Despite an excellent negative predictive value, CTA is a poor discriminator of patients with myocardial ischemia. Conversely, a normal stress PET study is a poor discriminator of patients without evidence of non-flow-limiting (subclinical) coronary atherosclerosis. These results suggest potentially complementary roles of CT and perfusion imaging in the evaluation of patients with suspected CAD. (J Nucl Cardiol 2007;14:799-809.)
Key Words: Computed tomography coronary angiography โข coronary artery disease โข positron emission tomography
Coronary artery disease (CAD) represents an enormous public health burden with respect to morbidity and mortality rates and cost. 1 The magnitude of CAD's impact has resulted in an accelerated evolution of imaging technology to improve the identification of at-risk individuals.
In patients with suspected or known stable CAD, management decisions hinge on the severity of symptoms and the magnitude of inducible myocardial ischemia. 2,3 Although the anatomic severity of epicardial coronary stenosis is generally associated with the degree of downstream myocardial ischemia, there is great individual variability. Isolated angiographic measures of stenosis severity (ie, diameter stenosis) are relatively modest indicators of coronary resistance, a key determi-From the Divisions of Nuclear Medicine/PET a and Cardiovascular Imaging,