ABC | Volume 113, Nº6, December 2019

Original Article Ket et al. Myocardial ischemia by SPECT and CCTA Arq Bras Cardiol. 2019; 113(6):1092-1101 Table 1 – Clinical characteristics of the participants Variables Group Age (years) 52.5 ± 9 Male sex, n (%) 17 (49) SAH, n (%) 31 ( 88) Diabetes Mellitus, n (%) 14 (40) Smoking, n (%) 5 (14) Dyslipidemia, n (%) 16 (45) Previous AMI, n (%) 9 (26) Typical chest pain, n (%) 10 (28) Atypical chest pain, n (%) 8 (22) Dyspnea, n (%) 11 (31) Altered stress test, n (%) 1 (2) Revascularization, n (%) 7 (20) CAD family history, n (%) 10 (28) SAH: Systemic arterial hypertension, AMI: Acute myocardial infarction; CAD: Coronary artery disease. Statistical analysis was performed using MedCalc ® statistical software (Version 18.5 – 64-bit; MedCalc Software bvba, Ostend, Belgium). Two-tailed p values < 0.05 were considered statistically significant. Results Clinical and demographic characteristics of the sample A total of 38 patients were selected; out of these, 35 were included in the study. Three patients were excluded: one patient due to long wait times to undergo the stress phase as a result of problems with schedule and other two due to technical problems in the Radiology Sector. Out of the 35 patients studied, with a mean age of 52.5 ± 9 years, 18 were women (51%). Table 1 shows the main clinical and demographic characteristics of the population analysed. Obstructive CAD assessment by CCTA In this study, obstructive CAD (stenosis > 50%) was present in 43% (n = 15) of the patients; non-obstructive lesions were identified in 57% (n = 20) of the patients. Perfusion defects on scintigraphy and CT The distribution of perfusion defects on both methods are shown in Table 2. Based on the data from Table 2, it was possible to observe a difference between the distribution of perfusion defects on scintigraphy and CT. A total of 57.1% (n = 20) of the patients presented perfusion defects at myocardial scintigraphy, with only half of them (28.5%; n = 10) also presenting defects at CT. On the other hand, when perfusion defects were not detected on scintigraphy (n = 15), in the majority of the cases (60.0%; n = 9), CT showed no perfusion defects. These data showed that CT perfusion imaging sensitivity was 70%, and SPECT sensitivity was 66% for detection of perfusion defects (Figure 2). Perfusion defects on scintigraphy in relation to obstructive CAD Based on the data in Table 3, it was possible to demonstrate a significant association between normal scintigraphy and absence of obstructive coronary lesions. Twenty patients had abnormal myocardial scintigraphy, and half of them (n = 10) also presented obstructive CAD at CCTA. Table 4 shows false-positive scintigraphy findings. In contrast, when scintigraphy was normal (n = 15), in most of the cases (66%), there was no presence of obstructive lesions on tomography; this association did not reach statistical significance (p = 0.49). According to these data, the sensitivity of scintigraphy for anatomical assessment by CTA was 66%, with a specificity of 50% (Figure 3). Perfusion defects on myocardial perfusion CT in relation to obstructive CAD Based on the data in Table 3, it is possible to show a significant association between abnormal CT and presence of obstructive coronary lesions. Out of all the patients, 54.2% (n=19) presented abnormal CT, and most of them (73.6%; n = 14) also presented coronary obstructive lesions on CT. In contrast, when perfusion tomographywas normal, which occurred in 45.7% (n=16) of the patients, in almost all the cases (93.7%, n=15), the tomography showed no obstructive lesions (p = 0.0001). According to these data, CT perfusion imaging sensitivity for the diagnosis of obstructive CAD was 93%, and specificity for detecting the absence of obstructive CAD on CCTA was 75% (Figure 3). Analysis of the area under the curve for obstructive CAD detection Myocardial perfusion with CT showed an AUC of 0.84 for the detection of obstructive CAD, with a confidence interval Table 2 – Perfusion defects on scintigraphy (SPECT) and myocardial perfusion CT (n = 35) Perfusion defects Positive myocardial perfusion scintigraphy Negative myocardial perfusion scintigraphy Positive CT myocardial perfusion 10 6 Negative CT myocardial perfusion 10 9 P = 0.73 (two-sided Fisher’s exact test). SPECT: Single-photon emission computed tomography; CT: computed tomography. 1095