Radionuclide imaging of cardiac autonomic innervation

Abstract

Cardiac autonomic function plays a crucial role in health and disease, with abnormalities both reflecting the severity of the disease and contributing specifically to clinical deterioration and poor prognosis. Radiotracer analogs of the sympathetic mediator norepinephrine have been investigated extensively, and are at the brink of potential widespread clinical use. The most widely studied SPECT tracer, I-123 metaiodobenzylguanidine ((123)I-mIBG) has consistently shown a strong, independent ability to risk stratify patients with advanced congestive heart failure. Increased global cardiac uptake appears to have a high negative predictive value in terms of cardiac events, especially death and arrhythmias, and therefore and may have a role in guiding therapy, particularly by helping to better select patients unresponsive to conventional medical therapies who would benefit from device therapies such as an ICD (implantable cardioverter defibrillator), CRT (cardiac resynchronization therapy), LVAD (left ventricular assist device), or cardiac transplantation. Cardiac autonomic imaging with SPECT and PET tracers also shows potential to assess patients following cardiac transplant, those with primary arrhythmic condition, coronary artery disease, diabetes mellitus, and during cardiotoxic chemotherapy. Radiotracer imaging of cardiac autonomic function allows visualization and quantitative measurements of underlying molecular aspects of cardiac disease, and should therefore provide a perspective that other cardiac tests cannot.

Patients With Continuous-Flow Left Ventricular Assist Devices Provide Insight in Human Baroreflex Physiology

“…10,25 Functional cardiac imaging studies with different tracers suggested that increased global cardiac uptake has a high negative predictive value in terms of cardiac events. 26 MSNA burst rates exceeding 49 bursts per minute were associated with reduced 1-year survival rates in 122 heart failure patients. 11 Our observation that resting MSNA was not profoundly increased compared with matched healthy controls is reassuring and indicates that continuousflow LVAD therapy might decrease sympathetic drive in heart failure patients.…”

Anthracycline-induced cardiomyopathy: The search continues

“…Recent reviews have summarized the mechanism by which I-123 MIBG is taken up by the nerve terminal, the utility of this agent, and the technical aspects of its imaging. [24][25][26][27] One of the strengths of the current study by dos Santos 28 is that all of the subjects were relatively young (mean age of 16), when identification of early anthracycline-induced cardiomyopathy would be most critical. The subjects were a median of 5.3 years out from their chemotherapy.…”

Cardiac autonomic imaging with SPECT tracers

“…Most autonomic radiotracers under investigation image pre-synaptic anatomy and function, illustrated in Figure 1 19,20 (although there is ongoing work on PET tracers that bind to post-synaptic a and b receptors). NE is produced in the pre-synaptic terminal, and is concentrated and stored in vesicles, often with ATP.…”