Introduction
Sarcoidosis is a rare multi-organ system granulomatous disease of uncertain aetiology. Cardiac sarcoidosis (CS) is clinically evident in 2%–7% of patients, but autopsy and imaging series report a substantially higher occurrence of 25%–80%.1–4 Accurate evaluation of active myocardial inflammation in patients with CS is important in the development of a treatment strategy.
Conventional methods to evaluate active CS include observation of new atrioventricular block5 6 or ventricular arrhythmias,7 8 a gradual decrease in the left ventricular ejection fraction (LVEF) on echocardiography,9 10 a positive finding on gallium scintigraphy11 or presence of specific positive biomarkers,4 12 which are known to have low accuracy.
18F-fluoro-2-deoxyglucose positron emission tomography (FDG-PET) preceded by fasting has been used to identify active inflammatory changes in CS.13–15 There have been several reports showing the association between abnormal FDG uptake and clinical symptoms6–8 10 or high serum level of ACE.13 14 However, even with strict prior carbohydrate restriction, physiological FDG accumulation can cause a false positive.
Compared with FDG-PET, cardiac magnetic resonance (CMR) imaging is more accessible, requires a shorter period of prior fasting, lacks radiation exposure, and is less expensive. Late gadolinium enhancement (LGE) is the gold standard for the diagnosis of CS, which represents both fibrosis/scarring and active infiltrative granulomas. High signal intensity on T2-weighted short-tau-inversion-recovery black-blood images (T2W-STIR-BB) indicates still water in the myocardium, which points to oedema associated with inflammation.16 17 The sensitivity of hyperintensity on T2-weighted images for diagnosing CS (34%) was reported to be not as high as that of FDG-PET, with fasting longer than 18 hours (48%–100%, >70% in most studies except for 2 out of 13 studies that showed <70%), or LGE (59%–100%, >70% in most studies except for four out of 42 studies that showed <70%).5 18 However, additional T2-weighted images or FDG-PET is needed to differentiate active and fibrotic lesions, since LGE is seen in both.4 19 In addition, the association between atrioventricular block and abnormal septal hyperintensity on T2-weighted images has been reported as shown in that with FDG-PET.5 Thus, such hyperintensity may be useful in identifying active patients with CS, however, the relationship between hyperintensity on T2W-STIR-BB images and abnormal myocardial FDG uptake on PET or other conventional diagnostic methods has not been fully evaluated.
The purpose of this study was to investigate the diagnostic performance of hyperintensity on T2W-STIR-BB images semi-quantitatively analysed using the myocardium-to-spleen ratio (MSR) in identifying active patients with CS in comparison to FDG-PET.