Recent Developments and Future Directions of Sympathetic Nervous Function Imaging

Abstract

An excess, long-lasting increase in systemic autonomic function facilitates myocardial injury and heart failure (HF), leading to lethal cardiac outcomes. Cardiac 123 I-labeled metaiodobenzylguanidine (MIBG) imaging enables non-invasive and quantitative evaluation of cardiac sympathetic innervation in human hearts. The independent and incremental prognostic values of this imaging technique in combination with clinical information in chronic HF patients have been shown. Results of recent multicenter MIBG studies performed in North-America, Europe and Japan have further strengthened the prognostic values, facilitating the clinical use of cardiac MIBG imaging in long-term management of chronic HF patients. Cardiac neuroimaging can contribute not only to the riskstratification for lethal events but also to appropriate selection of a therapeutic strategy using drug and device therapies, such as implantable cardioverter defibrillator (ICD) implantation and cardiac resynchronization therapy (CRT), in HF patients. Because of the limitations of current indication criteria, however, some patients undergoing ICD implantation and/or CRT receive no potentially beneficial intervention and, in contrast, some other patients have lethal outcomes without the benefits. Because of increases in medical costs due to noneffective or futile device therapy, the non-negligible number of non-responders to device treatment indicates the need for better selection of high-risk patients who can benefit most from device treatment in a cost-effective manner. Quantitative assessment of cardiac MIBG activity and kinetics can improve the identification of potential candidates for ICD/CRT and reduce costs associated with device treatments with a minimal impact on outcomes. A further large-scale investigation is needed to establish the possibility of cardiac MIBG imaging for more precisely selecting patients at increased risk or at low risk for potentially lethal arrhythmias, sudden cardiac death and/or refractory pump failure so as to optimize therapeutic interventions in patients with heart failure.