Stress Computed Tomography Myocardial Perfusion

Abstract

Coronary computed tomographic angiography (CTA) is establishing itself as a method that allows robust visualization of the coronary arteries in a noninvasive fashion. It is certainly not a widespread replacement for diagnostic invasive coronary angiography, nor a screening technique, but if image quality is adequate (which requires that state-of-theart equipment is used and adequate imaging protocols are applied) and patients are appropriately selected, coronary CTA is considered clinically useful in a number of welldefined situations (1-3). Such situations include patients presenting with acute chest pain at an intermediate likelihood of coronary artery disease, with an absence of electrocardiographic (ECG) changes and normal troponin values, or patients with stable chest pain at intermediate likelihood of coronary artery disease, but with equivocal stress test results. In numerous trials and meta-analyses, it has been shown that after appropriate patient selection and with sufficient experience, coronary CTA has a high sensitivity to detect coronary artery stenoses (4 -11). Consequently, in most published studies, the negative predictive value approaches 100%: if a coronary CTA study shows coronary arteries without plaque or stenoses, the false-negative rate is very low. See page 1072On the other hand, there are obvious drawbacks to coronary CTA. It cannot be reliably performed in all patients, and its somewhat limited spatial resolution makes it difficult to accurately assess stenosis degree (12-15). Overestimation of stenosis degree is not uncommon, and false-positive findings do occur, especially if image quality is not optimal. In addition, coronary CTA is an anatomic imaging method and as such shares the limitations of invasive angiography: when a stenosis is seen, it is still uncertain whether this specific lesion causes ischemia (16 -19)-usually considered a prerequisite to justify revascularization.Contrast-enhanced computed tomography (CT) imaging of the heart shows not only the coronary arteries, but also the myocardium. It has been shown that chronic hypoperfusion can easily be seen by CT, for example, in patients after myocardial infarction (20,21). Early data suggest that CT may also be able to detect stress-induced perfusion defects (22,23), and in this issue of the Journal, Blankstein et al. (24) present the first series of patients studied by adenosine-induced stress myocardial perfusion imaging using contrast-enhanced dual-source CT. In fact, their examination protocol was comprehensive and approached what some may be referring to as a "1-stop shop." Thirty-three patients who had a nuclear stress test and underwent invasive coronary angiography were studied by CT. The scan protocol consisted of an initial contrast-enhanced scan acquired during adenosine infusion, a second contrastenhanced scan acquired at rest, and a third scan performed without additional contrast. The initial adenosine stress contrast-enhanced scan served to visualize the coronary arteries and identify coronary artery stenose...

CT-Based Myocardial Perfusion Imaging-Practical Considerations: Acquisition, Image Analysis, Interpretation, and Challenges

“…The addition of SPECT-MPI to CTA has already been shown to result in improved specificity and positive predictive value (PPV) to detect hemodynamically significant coronary lesions in patients with chest pain [11] and to have the potential of avoiding un-necessary coronary revascularizations [12]. However, a combination of CTA and CT-based myocardial perfusion imaging (CTP) would have the advantage of using a single technological modality and has already been touted as the potential one-stop shop [13] for cardiac risk assessment. The combination of these CTbased modalities is being tested in a large multicenter, international study of 320-row detector CTP imaging (CORE320) which utilizes wide-area 320-row CT scanning in subjects referred for invasive coronary angiography (NCT00934037).…”