Arrhythmogenic myocardial scar localized through the combined use of 123I-mIBG SPECT and cardiac MRI

A 63-year-old male patient was referred to our Hospital due to sudden onset of palpitations and increased blood pressure, with basal ECG revealing a sinus tachycardia at 100 b/min and no other abnormalities. No history of cardiac symptoms or disease prior to this episode and no other relevant factors were reported. The patient underwent a dynamic ECG Holter monitoring that showed episodes of polymorphic not sustained ventricular tachycardia, preceded by tri-bigeminy ectopic ventricular beats. The patient was submitted to cardiac magnetic resonance (CMR) that was positive for myocardial scar localized in the proximal tract of infero-lateral wall of the left ventricle (LV) (Fig. 1). Since patient had not story of ischemic cardiopathy, this CMR finding was interpreted as myocyte injury caused by previous myocardial inflammation. Afterwards, the patient was administered with 185 MBq of 123I- mIBG (AdreViewTM, GE Healthcare) intravenously. Planar images were acquired at 15 min and 4 h after injection with dual-head -camera (Infinia®, GE Healthcare) equipped with low-energy, high-resolution collimators, and all acquisitions were performed with a 20% energy window centered at the 159-keV photopeak of 123 I. Furthermore, SPECT imaging of the chest was performed at 4 h, with a minimum of 30 projections per head, 20–30 s/projection, and a 64 × 64 matrix. Acquired images were transferred to a Xeleris® workstation (GE Healthcare) for elaboration. Heart to mediastinum (H/M) ratio, calculated on planar images according to the interna- tional guidelines, resulted of 1.94 at 15 min and 1.92 at 4 h. SPECT images demonstrated a segmental defect of 123I-mIBG uptake in the LV infero-lateral wall (Fig. 2). Emory Cardiac ToolboxTM wasapplied to obtain a 17-segment regional polar (bull’s-eye) map and a summed defect score (SDS) of 16 was calculated. Using a dedi- cated off-line co-registration software the corresponding SPECT and CMR slices were superimposed demonstrating a match between the scar tissue revealed by CMR and the regional abnormal uptake disclosed by SPECT (Fig. 3). After 2 weeks, the patient was submitted to CMR/SPECT-guided ablation of the ventricular arrhythmogenic focus. Dynamic ECG-monitoring performed 1 month after therapy revealed complete regression of the electrophysiological abnor- malities. Cardiac scintigraphy with 123I-mIBG is a well-established imag- ing method for predicting the arrhythmic events in chronic heart failure (HF).1 However, the phenomenon of sympathetic denerva- tion, consequent to post ischemic or phlogistic remodeling, resulted to be associated with increased risk of ventricular arrhythmia. In this context, the role of SPECT for the detection of regional defect of 123I-mBIG uptake has still to be defined.2 Of note, the ischemic and non-ischemic myocardial scars represent critical arrhythmo- genic substrates, whose early identification and treatment are of utmost importance. CMR represents an excellent imaging modal- ity, characterized by high anatomical contrast, for the localization of scar tissue. However, the usefulness of the combined use of 123I- mBIG SPECT and CMR for matching functional and structural data has not been still widely explored.3 The case we present confirmthe usefulness of this multimodality approach for the structural and functional identification of a non-ischemic arrhythmogenic focus, enabling a precise targeting for the ablative therapy.