Structural and function organization of intrathoracic extracardiac autonomic projections to the porcine heart: Implications for targeted neuromodulation therapy.

BACKGROUND

Mapping the structure/function organization of the cardiac nervous system is foundational for implementation of targeted neuromodulation-based therapeutics for the treatment of cardiac disease.

OBJECTIVE

The purpose of this study was to define the spatial organization of intrathoracic parasympathetic and sympathetic efferent projections to the heart.

METHODS

Yucatan mini-pigs (N = 11) were anesthetized and the thoracic cavity exposed. Electrical stimulation of the cervical vagi and stellate ganglia was performed individually, and hemodynamic responses were assessed in the intact state and after progressive debranching of each thoracic vagosympathetic trunk (VST). Subsequently, residual cardiac efferent projections arising from paravertebral chain ganglia (T1-T4) were evaluated by stimulation before and after individual ganglionic debranching.

RESULTS

Stimulation of the cervical vagi decreased heart rate and contractility while prolonging the activation-recovery interval (ARI). Stimulation of the stellate ganglia increased heart rate and contractility and decreased ARI. The majority of parasympathetic and sympathetic cardiac-evoked responses were mitigated after debranching of the right VST rostral to heart, whereas the left VST demonstrated a distribution with greater dispersion and caudal intrathoracic shift compared to the right. After complete thoracic VST debranching, stimulation of the T4 paravertebral chain ganglia demonstrated residual cardiac sympathetic efferent innervation to the heart in ∼50% of animals. That response was mitigated by transecting medial ganglionic branches.

CONCLUSION

The nexus point for optimum neuromodulation engagement of parasympathetic efferent projections to the heart is the cervical vagus and the T1-T2 paravertebral chain ganglia for sympathetic control. Removal of principal sympathetic efferent projections to heart requires targeting the T1-T4 regions of the paravertebral chain.