When blood flow to the heart muscle is restricted, the resulting discomfort often extends far beyond the chest. This sensation, known as referred pain, occurs because the heart muscle has relatively few dedicated sensory nerve endings for pain. When a lack of oxygen causes distress, such as during angina or a myocardial infarction (heart attack), the brain struggles to accurately pinpoint the source. Instead, the central nervous system misinterprets the distress signal as coming from other areas of the body that share the same neurological pathways. This neurological confusion causes the pain from a cardiac event to be felt in seemingly distant locations.
Mapping the Referred Pain: Specific Radiation Sites
The most widely recognized site for cardiac referred pain is the left arm, where the sensation typically travels down the inner side, sometimes reaching the elbow or even the pinky finger. This discomfort is often described as a deep ache, numbness, or a heavy, squeezing pressure, rather than a sharp, localized pain. While the left arm is common, the pain can also affect the right arm or both arms simultaneously.
The neck and jaw are also frequent targets for referred cardiac pain. Patients sometimes report a feeling of tightness, aching, or pressure that can be mistaken for a toothache or temporomandibular joint (TMJ) issue. This jaw pain may be felt on one or both sides, often pronounced in the lower jaw. The sensation can also extend into the throat, feeling like a choking or constricting discomfort.
Pain can also radiate backward to the upper back, often felt as a dull ache or crushing sensation between the shoulder blades. This discomfort is frequently dismissed as muscle strain or fatigue. A sensation that mimics severe indigestion or heartburn may also occur in the upper abdomen, or epigastric region, sometimes accompanied by nausea.
The Neurological Basis of Referred Pain
The phenomenon of referred cardiac pain is explained by the convergence-projection theory. Sensory nerves from the heart, known as visceral afferents, enter the spinal cord at the same levels as the somatic nerves that carry sensory information from the skin and muscles of the upper body. These heart nerves join the spinal cord primarily at the thoracic segments T1 through T4 or T5.
Once inside the spinal cord, both the visceral nerves from the heart and the somatic nerves from the arm, chest, and back synapse onto the same secondary neurons, which then relay the signal up to the brain. Since the brain receives far more sensory input from somatic structures (like the skin and muscles) than from internal organs, it is more familiar with interpreting signals from those areas. When the heart generates a pain signal, the brain misinterprets the ambiguous input, projecting the pain to the more commonly stimulated somatic region, such as the arm or jaw.
Recognizing Atypical and Silent Symptoms
While the classic chest-to-arm pain pattern is well-known, many cardiac events present with atypical or subtle symptoms that do not involve traditional chest discomfort. Women, for example, are more likely to experience symptoms like extreme fatigue, shortness of breath, or pain focused solely on the jaw, neck, or upper back. They may also report significant nausea or vomiting, which can lead to misdiagnosis as a digestive or flu-like illness.
People with diabetes have an increased risk of experiencing silent ischemia, where damage to the small nerves—a complication known as neuropathy—dampens or completely eliminates the pain signals. This means a myocardial infarction may occur with minimal or no noticeable pain at all. In elderly individuals, a heart attack may manifest simply as sudden confusion, lightheadedness, or an abrupt onset of breathlessness without any radiating pain.
Immediate Action Steps
If you or someone else experiences sudden, unexplained discomfort in the chest, arm, jaw, or upper back, or any combination of these symptoms, immediate action is necessary. Do not attempt to self-diagnose or wait for the symptoms to resolve, as prompt treatment significantly improves outcomes. Call 911 or your local emergency number immediately to activate emergency medical services.
While waiting for help to arrive, the person should sit down and remain as calm as possible. If the person is not allergic to aspirin and has not been advised against it by a healthcare provider, chewing one full-strength (325 mg) or four low-dose (81 mg) aspirin tablets can be beneficial. Aspirin works by slowing the clotting process, which can reduce damage to the heart muscle. Do not drive yourself or the person to the hospital, as ambulance personnel can begin life-saving treatment on the way.