Being a norepinephrine (NE) analog, mIBG replicates the same behavior as that of NE. A. From synapse mIBG is taken up by the presynaptic neurons;
because the ventricular myocardium is rich in sympathetic innervation, it shows prominent mIBG uptake. With each cycle of neuronal stimulation and NE
release, a small amount of mIBG reenters the cleft and leaks into the vascular compartment to be transported to the kidneys unchanged for excretion. In
heart failure (HF) patients, increased sympathetic outflow and decreased hNET1 efficiency results in faster clearance of neuronal mIBG. The images are
quantified as heart-to-mediastinum uptake ratio (H/M) and shows faster washout of mIBG activity between 15 minutes and 4 hours, with consequently
lower uptake ratio in the late images. Normal washout is 10% to 20% and the H/M ratio greater than 1.6; faster washout and low H/M are associated with
Source: NUCLEAR CARDIOLOGY, Hurst's The Heart, 14e
increased occurrence of adverse events such as HF progression, ventricular arrhythmogenicity, and cardiac death. Parts B–D demonstrate progressively
Citation:
Fuster
V, Harrington
Narula
J, Eapen
ZJ.allHurst's
The
Heart,
14e; 2017 with
Available
http://mhmedical.com/
Accessed:
July 31,
worsening HF
with lower
mIBG
uptake andRA,
higher
washout
rates;
patients
were
symptomatic
NYHAat:class
II to IIB and demonstrated
progressively
2017
99m
worsening H/M ratio. Parts E and F demonstrate single-photon emission computed tomography images; mIBG and
Tc-tetrofosmin in a patient without
© 2017
McGraw-Hill
Education.
rightsalternates
reserved between rows of mIBG and myocardial perfusion image slices. There is uniform
heart diseaseCopyright
(E) and an
ischemic
HF patient
(F). EachAll
display
uptake of both tracers in all myocardial walls of the normal patient. The HF patient has a perfusion defect in the basal inferolateral wall, consistent with a