Imaging sympathetic innervation.

The autonomic innervation of the heart modifies most cardiac functions. Especially the heart rate and the force of contraction of myocytes are modulated by the autonomic nervous system. A number of specific neurotransmitters interact with receptors on post- and presynaptic binding sites regulating the complex electromechanical system of the heart. Disturbances at this interaction result in a variety of cardioneuropathies. The clinical manifestations can be mild and may only consist of sporadic arrhythmias without hemodynamic effects. In some cases however the autonomic dysfunction may be severe, e.g. in the acute phase of the Guillain-Barré syndrome and in advanced diabetic neuropathy. At present, the only available techniques to visualise and quantitate disbalanced innervation of the myocardium are scintigraphic modalities as single photon emission tomography (SPECT) and positron emission tomography (PET) with appropriate radiopharmaceuticals. These methods are reviewed with respect to their possible clinical application and to future developments.