The use of prone imaging on acute resting gated myocardial perfusion imaging with Tc-99m sestamibi

NUCLEAR CARDIOLOGY BULLET The use of prone imaging on acute resting gated myocardial perfusion imaging with Tc-99m sestamibi Benjamin A. Lowenstein, MD,a Roger Pezzuti, MD,b and Mylan C. Cohen, MD, MPHa Case presentation. A 60-year-old obese man with hypertension and a family history of coronary artery disease, but without documented cardiac history, came to the emergency department (ED) with chest discomfort. His height and weight were 74 inches and 278 pounds, respectively. His examination, electrocardiogram, and cardiac enzyme levels in the ED were unremarkable. He was administered nitroglycerin sublingually, aspirin, and intravenous metoprolol without relief of his pain. Because of his ongoing pain and significant cardiac risk factors, an acute resting gated myocardial perfusion imaging study with technetium 99m sestamibi was obtained. Review of the raw data demonstrated a large body habitus, normal cardiac size, and diaphragmatic attenuation. Tomographic images (Figure 1 A) demonstrated a moderate-sized inferior defect from base to apex, which was worse at the base. Gated images revealed qualitatively normal left ventricular wall motion and contractility; the calculated ejection fraction was 41%, likely resulting from poor endocardial tracking. Diagnostic dilemma. The findings from scanning were abnormal. Typically, such a patient would be admitted to the hospital for serial cardiac enzyme assessment and stress testing if myocardial infarction were ruled out. However, on the basis of the review of these images, and what was believed to be diaphragmatic attenuation, the patient was brought back for further nongated imaging in the prone position. Subsequent imaging (Figure 1B) revealed uniform distribution of radionuclide in the left ventricular myocardium, and the test result was interpreted as normal. Discussion. Rapid risk stratification with myocardial perfusion imaging in low- to intermediate-risk From the Division of Cardiologya and Department of Radiology,b Maine Medical Center, Portland, Me. Reprint requests: Benjamin A. Lowenstein, MD, Division of Cardiology, Maine Medical Center, 22 Bramhall St, Portland, ME 04102; [email protected]. J Nucl Cardiol 2003;10:211-2. Copyright © 2003 by the American Society of Nuclear Cardiology. 1071-3581/2003/$35.00 ⫹ 0 doi:10.1067/mnc.2003.400

patients presenting to the ED with chest pain has allowed identification of high-risk patients to prevent serious adverse outcomes.1 Conversely, patients with normal scan results may, in most cases, be safely discharged from the ED with outpatient follow-up. Artifacts on “rest only” single photon emission computed tomography (SPECT) imaging are particularly difficult to interpret, as there is only one image. Artifacts involving the inferior wall on gated SPECT are well described in the literature.2 Inaccuracies have been attributed to the fluctuating height of the diaphragm, which causes varying degrees of attenuation of the inferior wall, simulating reversibility.3 The presence of diminished counts in the inferior wall was initially described with the use of planar imaging, particularly in the anterior and left lateral views.2 For SPECT imaging, the prone position favorably alters the spatial relationship of the heart and diaphragm and reduces inferior attenuation artifact.2,3 Prone imaging, which is not ideal as a single position because it increases the distance from the detector and may induce anterior wall artifacts, is thus used in combination with supine imaging.3,4 Segall and Davis2 directly compared prone versus supine imaging in thallium 201 stress testing and found a significantly improved specificity for defects involving the right coronary artery whereas specificity, sensitivity, and accuracy were not affected in the regions of the left anterior descending and left circumflex arteries. Conclusions. Rapid cardiac risk stratification with SPECT imaging is a helpful tool with which to identify patients who are at low risk and may be safely discharged from the ED, saving a costly hospitalization. Any means by which to improve this imaging technique will further our ability to accurately assess patients with acute chest pain. Prone imaging is well tolerated, reduces patient motion, does not add significant time to the examination, and decreases the false-positive rate of defects in the inferior wall. Prone imaging should be considered for all patients undergoing acute rest sestamibi imaging who have inferior defects on initial acquisition. 211

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Lowenstein, Pezzuti, and Cohen Prone imaging on acute resting gated myocardial perfusion imaging

Journal of Nuclear Cardiology March/April 2003

Figure 1. A, Tomographic images, supine position, demonstrating a moderate-sized inferior defect from base to apex. B, Subsequent tomographic images, with the patient in the prone position (using standard equipment) with his arms raised above the head, revealed uniform distribution of radionuclide in the left ventricular myocardium.

Acknowledgment The authors have indicated they have no financial conflicts of interest.

References 1. Kontos MC, Jesse RL, Schmidt KL, Ornato JP, Tatum JL. Value of acute rest sestamibi perfusion imaging for evaluation of patients

admitted to the emergency department with chest pain. Am J Cardiol 1997;30:976-82. 2. Segall GM, Davis MJ. Prone versus supine thallium myocardial SPECT: a method to decrease artifactual inferior wall defects. J Nucl Med 1989;30:548-55. 3. Lisbona R, Dinh L, Derbekyan V, Noavales-Diaz JA. Supine and prone SPECT Tc-99m MIBI myocardial perfusion imaging for dipyridamole studies. Clin Nucl Med 1995;20:674-7. 4. Perault C, Loboguerrero A, Liehn JC, et al. Quantitative comparison of prone and supine myocardial SPECT MIBI images. Clin Nucl Med 1995;20:678-84.