Clinical use of metaiodobenzylguanidine imaging in cardiology

Cardiac function is predominantly regulated by autonomic innervation. Many heart diseases involve alterations of cardiac adrenergic neurotransmission. In patients with cardiomyopathies, numerous therapeutic agents act directly or indirectly on cardiac adrenergic disorders. Metaiodobenzylguanidine (MIBG) imaging can provide in vivo information on one of the main components of adrenergic nerve function, i.e. the norepinephrine reuptake and storage system. Diminished MIBG uptake has been reported in patients with congestive heart failure, indicating an impaired norepinephrine reuptake and storage system. In patients with dilated cardiomyopathy (either idiopathic or ischemic), this alteration has been linked to the severity of the disease, evaluated on the basis of clinical or hemodynamic parameters. Moreover, MIBG imaging has been reported in such patients to be a potent prognostic marker in comparison with other recognized indices. After myocardial infarction, the decrease in MIBG uptake was transient in some patients and was suggested to be a viability indicator. Diminished MIBG uptake in ischemic patients was linked to the occurrence of ventricular arrhythmias. In patients with primary hypertrophic cardiomyopathy, decreased cardiac MIBG uptake has also been related to the clinical indices of severity. In patients suffering from various arrhythmias such as idiopathic ventricular arrhythmias, arrhythmogenic right ventricular cardiomyopathy or a long-QT syndrome, MIBG imaging has evidenced regional abnormalities of adrenergic nerve function and has provided new insights into the pathophysiological mechanisms of such disorders. Finally, MIBG scintigraphy may permit the evaluation of anthracyclin cardiotoxicity. Thus, MIBG imaging appears to be a promising tool for the cardiologist.