IJCS | Volume 33, Nº4, July and August 2020

392 Figure 1 – Gallium-67 SPECT of a 36-year-old female patient with newly-diagnosed left ventricular systolic dysfunction. Coronal and axial sections demonstrate accumulation of the radiotracer in the left ventricular lateral wall (long arrow) and in the interventricular septum (short arrow); endomyocardial biopsy confirmed the presence of granulomas of giant non-caseous cells compatible with active sarcoidosis. After steroid therapy systolic function improved and the follow-up scintigraphy was negative facilitate its distribution to distant services at reduced cost. Granulomas with giant cells are exquisitely avid for this radiotracer uptake ( Figure 1 ) and a positive gallium-67 scintigraphy is considered as a major criterion for the diagnosis of CS by the consensus of specialists of the HRS. 25 MRI As an advanced cardiac imaging modality, besides giving detailed assessment of biventricular function, CMR has the capacity to detect myocardial edema, perfusion abnormalities and to evaluate the presence and size of scar. The addition of T2 weighted imaging and T2 mapping give CMR the capacity to detect edema and inflammation and some have suggested could be an alternative to 18F-FDG PET(32) ( Figure 2 ). The use of gadolinium, an extracellular contrast agent, is recommended to evaluate the presence ofmyocardial scar as it demonstrates slower washout from areas of fibrosis and inflammation compared to normal myocardium. The pattern of late gadolinium enhancement (LGE) findings follows the same pathophysiological distribution of the areas of fibrosis, 33,34 with sometimes an extension into the RV insertion points. 35 CMR has the capacity to distinguish subcentimeter lesions and to differentiate between subepicardium, midmyocardium and subendocardium, due to its excellent in-plane spatial resolution. This distribution is helpful in recognizing CS, however it is not entirely specific and similar findings can be seen in other pathologies. CS have a tendency to spare the subendocardium, which is a common finding in ischemic cardiomyopathy with prior infarct. 35,36 CMR sensitivity for CS approaches 75-100% and its specificity 76-78%. 33,37 The prognostic capacity of LGE was studied in a previous study that analyzed 155 patients with systemic sarcoidosis who underwent CMR for workup of CS involvement. 12 The median follow-up time was 2.6 years and the primary end-points were death, aborted sudden cardiac death and appropriate implantable cardioverter defibrillator (ICD) discharge. They found the presence of LGE in 25.5% of the patients with a hazard ratio of 31.6 for the primary end-points and 33.9 for any event. Regarding the patients with no LGE, no one had an adverse event (except for one patient who died from pulmonary infection). Those findings suggested that in patients with SS, scar indicated by LGE was the best independent predictor of potentially lethal events, stronger than LVEF and end-diastolic volume with a very high negative predictive value for adverse outcomes, including arrhythmic events. Ise et al., 38 described in 43 consecutive LGE-positive patients that the presence of large-extent LGE (≥20% of left ventricular mass) correlated with absence of functional LV recovery following steroid therapy and higher risk of cardiac mortality, hospitalization for heart failure and life-threatening arrhythmias. 38 Wiefels et al. 18F-FDG PET/CT and cardiac sarcoidosis Int J Cardiovasc Sci. 2020; 33(4):389-400 Review Article