The cardiac plexus is a network of autonomic nerves at the base of the heart, formed by the cardiac branches of the vagus nerves (parasympathetic) and the cardiac branches of the cervical and upper thoracic sympathetic trunks (sympathetic). The superficial cardiac plexus lies between the aortic arch and the pulmonary trunk. The deep cardiac plexus lies posterior to the aortic arch. Both plexuses distribute to the sinoatrial node, atrioventricular node, and coronary arteries.
The cardiac plexus innervates the cardiac conduction system and coronary vasculature. Sympathetic stimulation via the cardiac plexus increases heart rate, conduction velocity, and myocardial contractility, and dilates coronary arteries. Parasympathetic stimulation slows heart rate and reduces conduction. Cardiac plexus disruption during cardiac surgery, thoracic surgery, or cervical sympathetic chain manipulation can cause post-operative arrhythmias. The afferent pain fibres from the ischaemic myocardium travel back through the cardiac plexus to T1-T4, explaining the referred pain of angina to the chest, arm, and jaw.
Surgical manipulation around the aortic root, cardiac plexus, and atrial walls during cardiac operations can cause post-operative sinoatrial dysfunction, atrial fibrillation, and conduction abnormalities from direct plexus disruption, contributing to the 30-40% rate of post-operative AF seen after cardiac surgery.
Visceral pain afferents from ischaemic myocardium travel through the cardiac plexus to sympathetic ganglia at T1-T4 and then through their white rami communicantes to the spinal cord, producing referred pain felt in the chest, medial arm, jaw, and upper back in the distribution of these spinal levels.
