How do we establish cardiac sympathetic nervous system imaging with I-mIBG in clinical practice? Perspectives and lessons from Japan and the US.

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