Small ganglia of average length= 0.8 cm, breadth= 0.4 cm and thickness= 0.2 cm were observed in the root of the neck, medial to the CST in the plexus formed by the cardiac nerves from the SCG, cord, MCG/VG and ICG/stellate ganglion.
Nicholas James Mizeres (1933) and Ellison and Williams (1969) described the cardiac branches from the ICG and called it as inferior cardiac nerve.  In this study, cardiac branches were seen in 33 cases.
The intrinsic cardiac nerves
are mostly found in the atrial wall.
Functional anatomy of the major cardiac nerves
Besides these branches, caudal vertebral cardiac nerves
are separated from this ganglion as well as cranial and caudal branches which form subclavian ansa and vertebral nerve (Getty, 1975; Dursun, 2000; Pather et al., 2006; Ozgel et al., 2009; Kawashima and Thorington 2011).
Koizumi K, Terui N, Kollai M, Brooks CM (1982) Functional significance of coactivation of vagal and sympathetic cardiac nerves
. Proceedings of the National Academy of Sciences of the U.S.A.
A case of retroesophageal right subclavian artery--with special reference to the morphology of cardiac nerves
. Acta Anat Nippon.
Also, not everyone's cardiac nerves
Effect of canine cardiac nerves
on heart rate, rhythm, and pacemaker location.
Efferent sympathetics come from T-1 to T-4 to the stellate and middle cervical sympathetic ganglion, the post-ganglionic fibers innervate the heart via the cardiac nerves
. Sympathetic control of the heart increases heart rate, in addition to atrial and ventricular contractility, and decreases conduction time from the atrium to the ventricle.
The action of electrical stimulation and of certain drugs on cardiac nerves
of the crab, Cancer irroratus.
Scientists studying cardiac nerves
have taken an important step toward explaining why aging diminishes the heart's ability to pump harder and faster under exertion.