Cardiac neurotransmission imaging

Cardiac neurotransmission imaging with SPECT and PET allows in vivo assessm ent of presynaptic reuptake and neurotransmitter storage as well as of regi onal distribution and activity of postsynaptic receptors. In this way, the biochemical processes that occur during neurotransmission can be investigat ed in vivo at a micromolar level using radiolabeled neurotransmitters and r eceptor ligands. SPECT and PET of cardiac neurotransmission characterize my ocardial neuronal function in primary cardio-neuropathies, in which the hea rt has no significant structural abnormality, and in secondary cardioneurop athies caused by the metabolic and functional changes that take place in di fferent diseases of the heart. In patients with heart failure, the assessme nt of sympathetic activity has important prognostic implications and will r esult in better therapy and outcome. In diabetic patients, scintigraphic te chniques allow the detection of autonomic neuropathy in early stages of the disease. In conditions with:a risk of sudden death, such as idiopathic ven tricular tachycardia and arrhythmogenic right ventricular cardiomyopathy, P ET and SPECT reveal altered neuronal function when no other structural abno rmality is seen. In patients with ischemic heart disease, heart transplanta tion, drug-induced cardiotoxicity, and dysautonomias, assessment of neurona l function can help characterize the disease and improve prognostic stratif ication, Future directions include the development of tracers for new types of receptors, the targeting of second messenger molecules, and the early a ssessment of cardiac neurotransmission in genetically predisposed subjects for prevention and early treatment of heart failure.