IJCS | Volume 33, Nº2, March / April 2020

189 Figure 1 - SPECT images. Mazzoletti et al. Myocardial ischemia: SPECT and 13 NH 3 PET/TC Int J Cardiovasc Sci. 2020; 33(2):188-191 Case Report CT test : the values were normal in the LAD and CDX territories, but pathological in the LCX territory (1,45). The patient was asymptomatic during the examination and there were no alterations in the ECG. Discussion Coronary anatomy and myocardial blood flow have been identified as independent prognostic factors in patients with stable CAD. 1 Frequently, these anatomical and physiological assessments are used as complementary techniques for risk stratification and clinical decision-making. 2 Nuclear methods such as SPECT with 99m Tc-tetrofosmin and cardiac PET/ CT with 13 NH 3 are among the most frequently used tools for myocardial perfusion assessment. However, some disadvantages of the SPECT imaging related to the presence of image artifacts, long duration of the examination and the possibility of underestimating the ischemic severity in patients with multivessel disease should be considered. 3 These negative issues can be avoided by using cardiac PET/CT study, which has shown high accuracy and enables the quantification of perfusion and determination of CFR, which means high sensitivity and high predictive value in coronary artery disease detection and small vessel disease. Myocardial perfusion PET is an important and appropriate test for patients in which CFR quantification is useful for patient management. 4 CFR has an important impact on the prognosis of the patient: an analysis of the association between CFR and cardiac mortality suggests an excellent prognosis for a CFR > 2 and a steady increase in cardiac mortality for a CFR lower than this value. 5 Much attention now is being devoted to the possibility of evaluating CFR with CZT-SPECT. This technique is very promising and recently, the WATERDAY study results were published demonstrating that the sensitivity, specificity, accuracy, positive and negative predictive value of CZT-SPECT were, respectively, 83.3, 95.8, 93.3, 100 and 85.7% for the detection of ischemia in comparison with 15 O-H 2 OPET. 6 Unfortunately, in our case, the results of CZT-SPECT images were not completely accurate because of the presence of diaphragmatic attenuation and the identification of a small area of inducible ischemia in the LCX territory. Therefore, it was suggested to the patient to undergo a 13 NH 3 PET/CT study, which was able to better define the results of the quite unclear SPECT MPI test. The PET scan result showed an important area of inducible ischemia in the LCX coronary territory (46%) and the CFR of this territory was estimated at 1.45, which confirmed