Multimodality imaging in ICD implantation decision making: 123-iodine metaiodobenzylguanidine imaging and cardiac magnetic resonance imaging

Introduction: According to guidelines, implantable cardioverter defibrillator (ICD) is recommended in prevention of sudden cardiac death (SCD) in heart failure (HF) patients (pts). Guidelines have several limitations because ICD indication is based mainly on left ventricular ejection fraction (EF). Recently, 123-iodine metaiodobenzylguanidine imaging (123-I MIBG) seems to identify, independently from EF, pts at high risk of SCD (heart/mediastinum (H/M) ratio < 1.6 and a summed score (SS)> 26). Hypothesis: Our aim is to assess the role of 123-I MIBG combined with cardiac MRI to predict malignant ventricular tachyarrhythmia in HF pts. Methods: we enrolled 69 pts, consecutively admitted to our hospital with diagnosis of HF and EF<35%, NYHA class II and III, who underwent 123-I MIBG imaging and cardiac MRI. Summed score (SS) of 26 was used as cut-off to identify high risk (group 1) versus low risk (group 2) pts. Late gadolinium enhancement (LGE) and number of segments with scars were evaluated in the 2 groups. All pts underwent to ICD implantation. We assessed ventricular arrhythmic (VA) events at 18 months follow-up. Results: 21 pts were included in group 1 and 48 pts in group 2. All baseline characteristics were similar in 2 groups. In group 1, H/M ratio was 1.47± 0.24 and in group 2 21.63 ± 0.27 (p=0.015). The percentage of the pts with LGE was 70.9 % in group 1 vs 39.1 % in group 2 (p=0.023). At 18 months follow-up VA events in group 1 were 19.05% vs 4.17% in group 2 (p < 0.037). Moreover VA events were statistically recorded greater in pts with both SS > 26 and LGE compared to pts with only SS >26 (46.7% vs 19.6%, p= 0.046). Conclusions: Our results seem to confirm that reduced 123-I MIBG uptake (H/M and SS) and presence of LGE are associated with the occurrence of life-threatening ventricular arrhythmias in HF patients independently from EF. The use of integrated imaging could be a useful tool in the future to increase the specificity of the selection of pts for ICD therapy.