ABC | Volume 114, Nº2, February 2020

Update Update of the Brazilian Guideline on Nuclear Cardiology – 2020 Arq Bras Cardiol. 2020; 114(2):325-429 Table 18 – Numerical classification of segmentary division of the left ventricular myocardium into 17 parts, in cross sections (slices ?) of the minor and long-vertical axes Regions/walls Distal/apical portion Middle portion Proximal/basal portion Anterior 13 7 1 Anteroseptal – 8 2 Inferoseptal – 9 3 Septal 14 – – Inferior 15 10 4 Inferolateral – 11 5 Anterolateral – 12 6 Lateral 16 – – Apex 17 – – Obs: apical region includes the apex and distal or apical portion of all walls (13,14,15,16). which case it is sometimes necessary to add another phase or stage, namely that of late redistribution or reinjection, interpreted in the same manner. Semiquantitative analysis: With the aim of numerically assessing the intensity of radiopharmaceutical uptake (perfusion), within the established standards (17-segment model), specific scores have been developed: a) perfusion – considers the following numerical scale: 0 = normal; 1 = mildly reduced radiopharmaceutical uptake; 2 = moderately reduced uptake; 3 = severely reduced uptake; 4 = absence of radiopharmaceutical uptake. Scores of 3 or 4 are normally associated with coronary stenosis of > 90%. Therefore, the higher the number of affected segments is; the more extensive the process; the higher the summed scores, and the greater the severity will be. This has an unquestionable prognostic value for patients with CAD. The following calculations are achieved by the sum of values attributed to each segment: the sum of the values attributed to each segment during the stress phase is known as the “summed stress score” ( SSS ); this is repeated during the baseline or redistribution phase to obtain the “summed rest/redistribution score” ( SRS ). The difference between the SSS and the SRS is known as the “summed difference score” ( SDS ). According to Hachamovitch et al. 56,57 numerical SSS values < 4 are considered normal ; between 4 and 8 , mildly abnormal ; between 9 and 13 , moderately abnormal ; and > 13 , severely abnormal . It is worth emphasizing that SSS values < 4 , which may not necessarily be zero, are understood as normal, because there are myocardial regions which show lower radiopharmaceutical concentrations in and of themselves and may, consequently, receive values other than zero. Quantitative analysis: Polar maps are two- or three- dimensional reconstructions of the LV, initially elaborated with the proposal of encompassing relative radiopharmaceutical distribution throughout the heart in a single image. They are shown in circular form, resembling a target, for which reason they are also known as “bull’s eye plots.” Radiopharmaceutical uptake, which is representative of perfusion, is shown on a color scale, with the LV apex occupying the center of the target, while basal regions of the heart are represented by the outermost circle of the target (Figure 10). Programs capable of reconstructing these images also allow for percentage quantification of areas with reduced uptake by comparing the images to a databank of normal individuals of the same age and sex. Perfusion defects may also be quantified by the number of pixels in a determined region and by existing standard deviations in relation to normal perfusion areas. We may also obtain polar maps with parameters relative to ventricular function, such as LV wall motility and systolic thickness. These methods of quantitative analysis serve as complements to assist in qualitative or semiqualitative visual analysis. Evaluation of ventricular function with perfusion agents: In a manner analogous to that described for perfusion study, segmentary contractile analysis of the LV makes use of motility and systolic thickness scores for each segment, also considering division into 17 segments, visualized in the cross sections of the minor axis (distal, mid-cavity, and proximal regions) and the long vertical axis (anteroapical and inferoapical regions). Numerical values are attributed. Analysis of motility of LV walls is performed directly on the computer monitor, making the subendocardial contour visible. Analysis of systolic thickness should be directed to the color scale chosen for a group of images. When thickness is within normal limits, the color increment is observed toward the bottom of the scale. Furthermore, it is possible to obtain percentage of thickness in each region. For distal and middle slices of the minor axis, as well as for the apex, average normal thickness is around 40%, with a score of zero (0) Thicknesses between 30% and 40% are interpreted as borderline; those between 20% and 30% receive a score of 1 (mild reduction); 10% to 20%, a score of 2 (moderate to severe reduction); and less than 10%, a score of 3 (absence of thickness) . In the proximal (or basal) cross section of the minor axis, thickness of around 20% is considered normal. A score of 1 is not used, but rather only scores of 2 and 3. Abnormalities in motility and thickness generally go hand-in- hand, with slight differences in gradation between the two (Table 19) and in the resulting sums. In some cases, we may observe discrepancy between results, for instance, following revascularization surgery and in the presence of left bundle branch block, in which the motility of the interventricular septum is compromised, whereas thickness is not. Whenever possible, analysis of ventricular function should be performed at the baseline phase and after stress, with the purpose of detecting additionally indicative alterations in stunned or hibernating myocardium. The validated scores, which have been previously described, are recommended. Regarding the effect of global analysis of LV systolic function, LVEF is the parameter with the best reliability, and scores predominantly concentrate on segmentary analysis. Furthermore, the subjective or qualitative assessment of images regarding results related to myocardial perfusion study, which have been previously described ( homogenous 347