Extracardiac neural remodeling in humans with cardiomyopathy

Abstract

Background: Intramyocardial nerve sprouting after myocardial infarction is associated with ventricular arrhythmias. Whether human stellate ganglia remodel in association with cardiac pathology is unknown. The purpose of this study was to determine whether cardiac pathology is associated with remodeling of the stellate ganglia in humans.

Methods and results: Left stellate ganglia were collected from patients undergoing sympathetic denervation for intractable ventricular arrhythmias and from cadavers, along with intact hearts. Clinical data on patients and cadaveric subjects were reviewed. We classified ganglia from normal, scarred, and nonischemic cardiomyopathic hearts without scar as NL (n=3), SCAR (n=24), and NICM (n=7), respectively. Within left stellate ganglia, neuronal size, density, fibrosis, synaptic density, and nerve sprouting were determined. Nerve density and sprouting were also quantified in cadaveric hearts. Mean neuronal size in normal, scarred, and nonischemic cardiomyopathic hearts without scar groups were 320 ± 4 μm(2), 372 ± 10 μm(2), and 435 ± 10 μm(2) (P=0.002), respectively. No significant differences in neuronal density and fibrosis were present between the groups. Synaptic density in ganglia from SCAR and NICM groups were 57.8 ± 11.2 μm(2)/mm(2) (P=0.084) and 44.5 ± 7.9 μm(2)/mm(2) (P=0.039), respectively, compared with the normal group, 17.8 ± 7 μm(2)/mm(2) (overall P=0.162). There were no significant differences in left stellate ganglia nerve sprouting or myocardial nerve density between the groups.

Conclusions: Neuronal hypertrophy within left stellate ganglia is associated with chronic cardiomyopathy in humans. Ganglionic and myocardial nerve sprouting and nerve density were not significantly different. These changes may be related to increased cardiac sympathetic signaling and ventricular arrhythmias. Further studies are needed to determine the electrophysiological consequences of extracardiac neuronal remodeling in humans.

Figure 1

Characterization of Myocardial Scar. Shown are representative gross and Trichrome Elastic von Giessen (Trichrome) images of a (A) normal and (B) infarcted heart from cadaveric subjects. Fibro-elastic tissue (blue), present in the infarcted heart is highlighted by black arrows. Representative images of multi-modal techniques used to determine the presence of scar in hearts of patients from whom stellate ganglia were collected. These included (C) computed tomography with arrows pointing to a region of apical scar and aneurysm; (D) positive emission tomography with arrows indicating a region decreased to absent radiolabeled glucose uptake corresponding to scar; (E) magnetic resonance imaging with arrows indicating delayed gadolinium enhancement indicating scar, and (F) endocardial electro-anatomic map with gray areas (shown by arrows) indicating regions with voltage <0.5mV corresponding to myocardial scar.

Figure 2

Stellate Ganglion Neurons in The Presence of Cardiac Pathology. (A) Representative images of stellate ganglia stained with Thionin for NL, SCAR, and NICM. (Magnification 40x, Scale bar: 50μm). (B) Quantifications of mean neuronal size from Thionin staining. Solid purple line connects the means. (C) The Percentage of small (<350μm²), medium (350μm²-500μm²), and large (>500μm²) neurons is shown in for NL, SCAR, and NICM. Solid purple line connects the means

Figure 3

Stellate Ganglion Fibrosis and Neuronal Density. (A) The severity of stellate ganglion fibrosis in NL, SCAR, and NICM. (B) A comparison of the mean density of neurons for the groups is depicted. Solid purple line connects the means.

Figure 4

Synaptic Density and Nerve Sprouting Within Stellate Ganglia. Panel (A) shows representative images of synaptophysin(SYN) and growth-associated protein-43 (GAP43) Immunoreactivity in NL, SCAR, and NICM. Arrows indicate punctate structures staining darkly for synaptophysin. (B) and (C) Quantification of synaptophysin and GAP43 Immunoreactivity, respectively, amongst the groups. (Magnification 20x, Scale bar: 100μm).

Figure 5

Intra-myocardial Nerve Density. (A) Representative images of S100 nerve staining within myocardium from NL and SCAR. Black arrows depict nerve bundles, tracts, or fibers within the myocardium. Blue arrows show regions of intra-myocardial scarring. (B) Quantification of nerve density in NL and SCAR myocardium expressed as μm²/mm² of S100 Immunoreactivity. Solid purple line connects the means. (Magnification 20x, Scale bar: 100μm).