Why can a heart attack cause pain in the left arm?

The answer

Referred pain occurs because sensory nerve fibers from different parts of the body converge on the same neurons in the spinal cord. During a heart attack, pain signals from the heart travel along the same spinal cord pathways (T1-T5 segments) as sensory nerves from the left arm, shoulder, and jaw. The brain, which has limited ability to distinguish between these converging inputs, often misinterprets the cardiac pain as originating from the skin and muscles of the arm. This phenomenon, called viscerosomatic convergence, also explains why gallbladder pain can be felt in the right shoulder, kidney stones can cause groin pain, and diaphragm irritation can be experienced as shoulder tip pain. Understanding referred pain patterns is clinically vital for diagnosing internal organ problems.