MIBG Scintigraphy as a Tool for Selecting Patients Requiring Implantable Cardioverter Defibrillator (ICD)

The survival benefit provided by implantable cardioverter defibrillator (ICD) for primary prevention of sudden cardiac death in heart failure compared to medical treatment alone is well established. First limited to the most severe patients, the indications have gradually been extended in accordance with the results of more recent studies. This beneficial effect in terms of public health is accompanied by an increase in health spending which threatens to grow strongly at short and medium term. However, the majority of ICDs implanted will not be solicited because of the overall low incidence of severe ventricular arrhythmias in the population meeting the implantation criteria. To optimize our resources, it is therefore important to better assess the risk of sudden death in those patients candidates for ICD implantation.

The overactivation of NEURO-humoral systems plays an important role in the progression of heart failure, and in the occurrence of ventricular arrhythmias. The iodine-123 meta-iodobenzylguanidine scintigraphy (MIBG), is a functional imaging method that can noninvasively evaluate cardiac sympathetic innervation. It has been shown that cardiac adrenergic hyperactivation estimated by MIBG scintigraphy was associated with a poor outcome, and that its value was independent and superior to other prognostic factors in heart failure. More importantly, the risk of occurrence of major cardiac events is minimal when the cardiac uptake of MIBG is high. Furthermore, plasma natriuretic peptides (particularly BNP and NT-proBNP), which are other indicators of the NEURO-hormonal activation used in the diagnosis and assessment of prognosis in heart failure, are predictive of the risk of occurrence of sudden death in the same population. In summary, the MIBG scintigraphy and NT-proBNP are two prognostic markers in heart failure related to the degree of NEURO-hormonal dysfunction, and have a good negative predictive value of mortality. Their combined use could therefore help identify patients at low risk of severe arrhythmias.These tests are not currently part of heart failure diagnosis in patients who are candidates for ICD implantation.