SPECT/PET myocardial perfusion imaging versus coronary CT angiography in patients with known or suspected CAD.

Stress SPECT myocardial perfusion imaging (MPI) is the most commonly utilized stress imaging technique for patients with suspected or known coronary artery disease (CAD) and has a robust evidence base including the support of numerous clinical guidelines. Gated SPECT is a well-established noninvasive imaging modalities that is a core element in evaluation of patients with both acute and stable chest pain syndromes. Over the past decade, PET has become increasingly used for the same applications. By comparison, cardiac computed tomography (CT) is a more recently developed method, providing non-invasive approaches for imaging coronary atherosclerosis and coronary artery stenosis. Non-contrast CT for imaging the extent of coronary artery calcification (CAC), in clinical use since the mid-1990's, has a very extensive evidence base supporting its use in CAD prevention. While contrast-enhanced CT for noninvasive CT coronary angiography (CCTA) is relatively new, it has already developed an extensive base of evidence regarding diagnosing obstructive CAD and more recently evidence has emerged regarding its prognostic value. It is likely that non-contrast CT or CCTA for assessment of extent of atherosclerosis will become an increasing part of mainstream cardiovascular imaging practices as a first line test. In some patients, further ischemia testing with MPI will be required. Similarly, MPI will continue to be widely used as a first-line test, and in some patients, further anatomic definition of atherosclerosis with CT will also be appropriate. This review will provide a synopsis of the available literature on imaging that integrates both CT and MPI in strategies for the assessment of asymptomatic patients for their atherosclerotic coronary disease burden and risk as well as symptomatic patients for diagnosis and guiding management. We propose possible strategies through which imaging might be used to identify asymptomatic candidates for more intensive prevention and risk factor modification strategies as well as symptomatic patients who would benefit from referral to invasive coronary angiography for consideration of revascularization.

Serial changes on quantitative myocardial perfusion SPECT in patients undergoing revascularization or conservative therapy.

BACKGROUND: Little is known about changes of myocardial perfusion in patients undergoing coronary revascularization or medical therapy. The purpose of this observational study was to assess the long-term effects of revascularization or conservative therapy on serial quantitative myocardial perfusion single photon emission computed tomography (SPECT). METHODS AND RESULTS: The study population consisted of 421 patients who underwent serial rest thallium-201/stress technetium-99m sestamibi dual-isotope myocardial perfusion SPECT with at least a 1-year interval between the 2 studies and who had abnormal quantitative scan results on the first stress SPECT. The mean interval between scans was 32.7 +/- 15.9 months. Patients were divided into 3 groups according to stress defect extent: group 1 had small stress defects (4%-10%, n = 145), group 2 had intermediate stress defects (>10%-20%, n = 144), and group 3 had extensive stress defects (>20%, n = 132) at baseline. Forty patients in group 1, 44 in group 2, and 54 in group 3 underwent coronary revascularization between 2 SPECT studies; the others had conservative therapy. In group 3 patients with revascularization, stress defect extent and reversible defect extent were remarkably reduced (14.5% +/- 13.6% and 13.1% +/- 12.5%, respectively; both P <.0001), with greater improvement in those patients reporting increased use of cardiac medications; resting defect extent was slightly reduced (1.9% +/- 6.4%, P <.05). In group 3 patients with conservative therapy, a small reduction in stress defect extent was noted (2.3% +/- 8.3%, P <.05). In group 2, there were modest, similar reductions in reversible defect extent in both the patients with revascularization (2.7% +/- 7.7%, P <.05) and those with conservative therapy (1.8% +/- 7.3%, P <.05), as well as a small but significant reduction in stress defect extent in those with conservative therapy (2.1% +/- 8.2%, P <.05). In group 1 patients, no significant changes in stress, rest, or reversible defect extent were found with either therapy. CONCLUSIONS: The findings of this study show that improvement in quantitative myocardial perfusion abnormalities over time occurs in some patients with either revascularization or conservative therapy and suggest that, in patients with extensive defects, greater improvement may be seen in those who undergo revascularization.

Nuclear cardiology and electron-beam computed tomography: competitive or complementary?

Electron-beam computed tomography (EBCT) and nuclear cardiology techniques are both valuable in the noninvasive assessment of patients with suspected coronary artery disease. The techniques, however, are different in the information they provide about the patient. EBCT provides anatomic information on coronary atherosclerosis, whereas myocardial perfusion single-photon emission computed tomography assesses the physiologic significance of coronary stenosis. Because of these differences, the techniques are highly complementary. In considering the complementary nature of these methods, it is important to clarify the issues being raised. An important question in the consideration of a patient with known or suspected coronary artery disease is, What is the risk in an individual patient of developing clinical coronary artery disease? The answer to this question will determine who needs aggressive medical management. A second question in a suspected coronary artery disease patient is, What is the risk of cardiac death? As will be discussed, this risk, in general, determines the need to consider coronary revascularization. In the former question, EBCT testing and clinical assessment alone is usually sufficient, and in some cases nuclear testing can be of additional value. In answering the second question, on the basis of currently available data, the EBCT and nuclear cardiology studies appear to be operating in a complementary fashion.

Quantitative assessment of motion artifacts and validation of a new motion-correction program for myocardial perfusion SPECT.

UNLABELLED: Patient motion during myocardial perfusion SPECT can produce images that show artifactual perfusion defects. The relationship between the degree of motion and the extent of artifactual perfusion defects is not clear for either single- or double-head detectors. Using both single- and double-head detectors and quantitative perfusion SPECT (QPS) software, we studied the pattern and extent of defects induced by simulated motion and validated a new automatic motion-correction program for myocardial perfusion SPECT. METHODS: Vertical motion was simulated by upward shifting of the raw projection datasets in a returning pattern (bounce) and in a nonreturning pattern at 3 different phases of the SPECT acquisition (early, middle, and late), whereas upward creep was simulated by uniform shifting throughout the acquisition. Lateral motion was similarly simulated by left shifting of the raw projection datasets in a returning pattern and in a nonreturning pattern. Simulations were performed using single- and double-head detectors, and simulated motion was applied to projection images from 8 patients who had normal 99mTc-sestamibi SPECT findings. Additionally, images from 130 patients with actual clinical motion were assessed before and after motion correction. The extent of perfusion defects was assessed by QPS, and a 20-segment, 5-point scoring system was used to assess the effect of motion on the presence and extent of perfusion defects. RESULTS: Of 12 bounce simulations, the bouncing motion failed to produce significant (>3%) perfusion defects with either the single- or the double-head detector. With the single-head detector, early shifting created the largest defect, whereas with the double-head detector, shifting during the middle of the acquisition created the largest defect. With regard to upward creep, defects were of larger extent with the double- than the single-head detector. With the single-head detector, 8 of 20 simulated motion patterns yielded significant perfusion defects of the left ventricle, 7 (88%) of which were significantly improved after motion correction. With the double-head detector, 12 of 20 patterns yielded significant defects, all of which improved significantly after correction. Of 2,600 segments in the 130 patients with actual clinical motion, only 1.3% (30/2,259) of segments that were considered normal (score = 0 or 1) changed to abnormal (score = 2-4) after motion correction, whereas 27% (92/341) of abnormal segments were reclassified as normal after motion correction. CONCLUSION: Artifactual perfusion defects created by simulated motion are a function of the time, degree, and type of motion and the number of camera detectors. Application of an automatic motion-correction algorithm effectively decreases motion artifacts on myocardial perfusion SPECT images.

The Vaccine Adverse Event Reporting System (VAERS).

Immunizations against most vaccine-preventable diseases will be needed indefinitely unless the disease is eradicated. Public acceptance of immunizations may be threatened as vaccine coverage increases and disease decreases, however, due to the increase in both causally and coincidentally related vaccine adverse events. The post-marketing surveillance for such events in the USA in response to the mandatory reporting requirements of the National Childhood Injury Act of 1986. While VAERS has many methodological limitations intrinsic to such systems, it can play an important role in helping to monitor vaccine safety and maintain public confidence in immunizations.