140 [123I]MIBG scintigraphy was performed following European guidelines.21 The [123I]MIBG tracer, a norepinephrine analog, is absorbed by cardiac sympathetic nerves and accumulates in presynaptic vesicles without further metabolism.22 This allows evaluation of myocardial sympathetic innervation through subsequent scintigraphy imaging (Fig. 1). Abnormal results were defined as: Heart-tomediastinal uptake ratio (H/M) ≤1.6 and/or ≥20% myocardial wash-out rate after 4 hours. These criteria indicate impaired sympathetic neuron activity, which is often linked to autonomic dysfunction or heart failure. Imaging highlights diminished uptake or accelerated washout, reflecting alterations in norepinephrine reuptake or release. Patients with decreased [123I]MIBG uptake were classified as having SCAD.23 Fluordeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) FDG PET/CT examination was performed with a TF-64 combined PET/CT device (Philips Gemini, Medical systems, Eindhoven, the Netherlands) as described previously.24 Patients were instructed to have a carbohydrate-restricted diet for 24 h followed by a fast of at least 6 h before injection of FDG. Dosage was based on body weight. 50 IEH/kg unfractionated heparin was pre-administered intravenously to suppress physiologic uptake in the myocardium, with a maximum of 5000 IE. Cardiac magnetic resonance imaging CMR images were acquired using a 1.5 T Philips MRI scanner with an eight-element phase array cardiac coil. A vector electrocardiographic system was used for cardiac gating. A stack of short-axis cine slices of both the right and left ventricle (8-mm thickness, no gap) from the base to the apex of the entire heart were acquired. If performed, T2-weighted short-tau inversion recovery images (indication myocardial oedema) with 8-mm slice thickness were acquired at short-axis orientation. Late gadolinium enhancement (LGE) images were obtained 12-20 min after intravenous administration of 0.4 ml/kg gadolinium.24 Clinical data Patient characteristics, clinical diagnoses, and outcomes of carvedilol treatment were retrospectively analyzed. Data on age, sex, body mass index (BMI), and sarcoidosis-related factors (e.g., treatment history, presence of cardiac sarcoidosis, and FDG PET/CT findings) were collected. The presence of SCAD symptoms and evidence of SFN, based on documented clinical diagnoses, were also included. 9 146 9
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