Scintigraphic assessment of regional cardiac adrenergic innervation.

Abstract

To assess the feasibility of noninvasively imaging the regional distribution of myocardial sympathetic innervation, we evaluated the distribution of sympathetic nerve endings, using 123I metaiodobenzylguanidine (MIBG), and compared this with the distribution of myocardial perfusion, using 201Tl. Twenty dogs were studied: 11 after regional denervation, and nine as controls. Regional denervation was done by left stellate ganglion removal, right stellate ganglion removal, and application of phenol to the epicardial surface. Computer-processed functional maps displayed the relative distribution of MIBG and thallium in multiple projections in vivo and excised heart slices in all animals. In six animals, dual isotope emission computed tomograms were acquired in vivo. Tissue samples taken from innervated and denervated regions of the MIBG images were analyzed for norepinephrine content to validate image findings. Normal controls showed homogeneous and parallel distributions of MIBG and thallium in the major left ventricular mass. In the left stellectomized hearts, MIBG was reduced relative to thallium in the posterior left ventricle; whereas in right stellectomized hearts, reduced MIBG was in the anterior left ventricle. Phenol-painted hearts showed a broad area of decreased MIBG extending beyond the area of phenol application. In both stellectomized and phenol-painted hearts, thallium distribution remained homogeneous and normal. Norepinephrine content was greater in regions showing normal MIBG (550 +/- 223 ng/g) compared with regions showing reduced MIBG (39 +/- 44 ng/g) (p less than 0.001), confirming regional denervation. Combined MIBG-thallium functional maps display the regional distribution of sympathetic innervation. This new ability to noninvasively map the distribution of sympathetic nerves with simultaneous comparison to regional perfusion may provide important new insights into mechanisms, whereby an imbalance in sympathetic activity may relate to clinical disorders.

Neural regulation of the proinflammatory cytokine response to acute myocardial infarction

“…The available literature strongly supports that assumption. Phenol application to the epicardial surface has been employed for selective cardiac sympathetic afferent (5,34,37) and efferent (11,28,35) denervation based on anatomic observations (5) that the cardiac sympathetic afferent fibers course more superficially over the epicardial surface of the heart, whereas vagal afferent fibers run deeper until they reach the epicardial surface in the region of the atrioventricular groove. Most of these studies (5,34,35,37) have been performed in acute preparations like the present one.…”

Heterogeneous Sympathetic Innervation Influences Local Myocardial Repolarization in Normally Perfused Rabbit Hearts

“…13 Scintigraphic imaging in each of the phenol-treated rabbits demonstrated a heterogeneous distribution of MIBG uptake (innervation) and a homogeneous distribution of MIBI uptake (perfusion). Previous studies of MIBG uptake in the phenol model have shown that the reduction in uptake is due to an absence of sympathetic nerve terminals, or denervation.…”

“…The 2 autoradiographs were compared on a pixel-by-pixel basis by a color method described previously. 13 Color slices were then aligned to create a set of 3D reconstructions of the heart.…”

Use of a Single 11C-Meta-Hydroxyephedrine Scan for Assessing Flow–Innervation Mismatches in Patients with Ischemic Cardiomyopathy

“…Ther e has been long-standing interest in noninvasive imaging of myocardial sympathetic innervation for the prediction of life-threatening ventricular arrhythmias or implantable cardioverter defibrillator discharges using PET (1)(2)(3)(4)(5) or SPECT (6)(7)(8). It has been shown (9)(10)(11) that, in myocardial infarction, the area of reduced innervation often exceeds the area of reduced myocardial blood flow (MBF) (9)(10)(11)(12)(13)(14).…”