[TA] part of the cardiopulmonary splanchnic nerves from the second to fifth segments of the thoracic sympathetic trunk that pass medially and anteriorly to enter the cardiac plexus; they convey postsynaptic sympathetic fibers to, and visceral afferent (pain) fibers from, the heart. SYN: rami cardiaci thoracici gangliorum thoracicorum [TA], nervi cardiaci thoracici, thoracic cardiac nerves, upper thoracic splanchnic nerves.