A key problem in ischemia-induced impairment of the vascular performance of
the diabetic heart is the often-unrecognized cardiac sympathetic dysfuncti
on. Advanced single-photon emission computed tomography (SPECT) and positro
n emission tomography (PET) using the radiopharmaceuticals, I-123-metaiodob
enzylguanidine (I-123-MIBG) and C-11-hydroxyephedrine (C-11-HED), have show
n that dysfunction of cardiac sympathetic nerves is present to a large exte
nt in both type I and type 2 diabetes. The pattern of sympathetic disturban
ces is heterogeneous with a predominant effect in the posterior myocardial
region. Furthermore, myocardial blood flow assessment with PET has shown th
at endothelial-dependent vasodilatation is reduced in proportion to the mag
nitude of cardiac sympathetic dysfunction. These mechanisms are currently p
roposed to lead from early changes to advanced impairment of cardiac functi
on in diabetes. Copyright (C) 2001 John Wiley & Sons, Ltd.