Cardiac pain is classically referred to the left arm and precordium. Which pathway best explains this referral?

• A Visceral afferents traveling with cardiac branches of the vagus to the nucleus tractus solitarius
• B Diaphragmatic irritation transmitted through the phrenic nerve to C3, C4, C5
• C Direct irritation of the brachial plexus by pericardial inflammation
• D Visceral afferents running with sympathetic fibers to spinal cord segments T1 to T5, converging with somatic afferents from the same dermatomes ✓

Explanation

Pain afferents from the heart travel with the sympathetic cardiac nerves to the upper thoracic spinal cord (mainly T1 to T5). Because these visceral afferents enter the same segments that receive somatic sensory fibers from the chest wall and medial arm, cortical convergence produces referred pain in those dermatomes. Vagal afferents mediate reflex responses such as bradycardia rather than conscious pain localization.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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