Cardiac denervation is associated with progressive left ventricular (LV) dysfunction, ventricular arrhythmias, and sudden cardiac death (SCD) in heart failure (HF). In this regard, it is important to evaluate cardiac-specific sympathetic nervous system (SNS) function. The radiotracer Iodine-123 meta-iodobenzylguanidine (123I-mIBG) can noninvasively evaluate pre-synaptic SNS function. Recent multicenter trials have shown 123I-mIBG to have strong predictive value for fatal arrhythmias and cardiac death in HF. 123I-mIBG was initially developed in the USA in the 1970s. In 1992, the Japanese Ministry of Health and Labour approved 123I-mIBG for the assessment of cardiac function. Following approval, the Japanese nuclear cardiology community developed 123I-mIBG imaging services in various medical centers. Japanese groups have been trying to establish the clinical utility of 123I-mIBG and standardize parameters for data acquisition and image analysis. The US Food and Drug Administration (FDA) has approved clinical use of 123I-mIBG for cardiac and non-cardiac imaging. However, clinical use of 123I-mIBG in the US has been very limited. The number of 123I-mIBG studies in Japan has also been limited. There are similarities and differences between the two countries. To establish the clinical utility of 123I-mIBG in both countries, it is important to characterize the situations of 123I-mIBG in each.
