SCINTIGRAPHIC EVALUATION OF CARDIAC AUTONOMIC INNERVATION

Alterations in cardiac autonomic neuronal function have become the foc us of intense research in various cardiovascular diseases. Both single -photon emission tomography (SPECT) and the positron emission tomograp hy (PET) imaging techniques in combination with radiolabeled neurotran smitters and receptor ligands have become available for the scintigrap hic visualization of presynaptic and postsynaptic neuronal function. S everal clinical studies have shown changes in tracer distribution in d ifferent clinical conditions, such as ischemic heart disease, congesti ve heart failure, malignant arrhythmias, heart transplantation, and in patients with diabetes. In patients with congestive heart failure, pr evious in vitro investigations have concentrated on the postsynaptic l evel of the sympathetic innervation. However, alterations in presynapt ic nerve function have been demonstrated with scintigraphic investigat ions by decreased presynaptic tracer retention. Moreover, correlation between scintigraphic findings and clinical outcome was shown in patie nts with heart failure, providing important prognostic information sup erior to conventional risk assessment. In conclusion, scintigraphic ev aluation by SPECT and PET allows functional characterization of cardia c presynaptic and postsynaptic neurons. Regional tracer uptake can be used as an index for the integrity of innervation in various diseases. Newer tracer approaches may allow the noninvasive quantification of n euronal function by PET.