New SPECT and PET Radiopharmaceuticals for Imaging Cardiovascular Disease
Table 9
SPECT Radiotracers for Imaging Autonomic Dysfunction in Heart Failure.
123I-Meta-Iodobenzyl Guanidine (123I-MIBG) (i) 123I-MIBG targets presynaptic sympathetic neurons (ii) differs from physiological norepinephrine in three key ways (Figure 11): (1) does not interact with post-synaptic - or -adrenergic receptors (2) does not undergo post-synaptic catechol-O-methyl transferase (COMT) metabolism into normetanephrine (NMN) (3) does not interact with α2c presynaptic receptors that regulate norepinephrine release (iii) conversely 123I-MIBG does mimic norepinephrine in its escape from the synaptic cleft into the blood pool