How heterogeneous is the cardiac autonomic innervation?

The rich autonomic innervation of the heart plays an important role in modifying cardiovascular function. Recently developed in vivo scintigraphic imaging techniques allow for visualization of the autonomic innervation of the heart. Studies using the modalities have shown heterogeneity of sympathetic innervation in various kinds of pathological conditions as well as normal human heart. The inferioposterior region shows typically less sympathetic innervation than the anterior region. In addition, neuropathic processes appear to commence in inferior-apical regions extending towards the base of the heart. Arrhythmogeneity has been related to the heterogeneous innervation of the heart and heterogeneous uptake of radiolabeled catecholamine analogues, such as I-123 metaiodobenzylguanidine, can be found in patients with arrhythmia. In dilated cardiomyopathy, reduced uptake indicates a poor prognosis which allows risk stratification for patients with heart failure. Heterogeneity of the reinnervation process following heart transplantation has also been investigated. Evidence was found of reinnervation primarily in the basal anterioseptal region and to a lesser degree in the inferioposterior and apical regions. Tracer approaches are uniquely suited to identify regionally altered innervation and provide tools for linking information on cardiac autonomic innervation with other clinical aspects.