A heart attack, known medically as a myocardial infarction, occurs when blood flow to a section of the heart muscle is severely reduced or blocked, often due to a clot forming over a ruptured plaque in a coronary artery. This lack of oxygen causes tissue damage, demanding immediate medical attention. A heart attack can manifest with various symptoms, including pain that radiates to the shoulder or arm, a phenomenon known as referred pain. Understanding where this pain is felt and why it occurs can be life-saving information.
The Location of Referred Pain
The pain associated with a heart attack most commonly affects the left side of the body, spreading to the left shoulder, arm, or side of the chest. This discomfort often begins as pressure, fullness, or aching in the center or left side of the chest, then moves outward. The sensation in the shoulder or arm is typically described as a dull ache, tightness, or a heavy, crushing feeling, rather than a sharp, localized pain.
The pain can travel down the inside of the left arm, sometimes presenting as numbness or tingling, and may extend all the way to the jaw, neck, or back. While the left side is the most frequent location, heart attack pain can occasionally manifest only on the right side or in both arms and shoulders. This cardiac-related shoulder pain tends to persist and does not subside with rest or by changing position, which is common for musculoskeletal issues.
Understanding Referred Pain (The Mechanism)
The reason a heart problem can cause pain in the shoulder and arm is due to a neurological process called referred pain. This occurs because the nerves carrying sensory information from the heart share pathways in the spinal cord with nerves that relay sensation from the arm, shoulder, and other areas. The sensory nerve fibers from the heart are not precise at localizing pain, unlike nerves in the skin or muscles.
Specifically, the sensory nerve fibers from the heart follow the sympathetic nervous system back to the spinal cord segments, primarily from T1 to T5. Nerves from the chest, shoulder, and inner arm also enter the spinal cord at these same segments. This convergence of signals means the brain receives a distress message from the T1-T5 region but cannot distinguish the exact source.
The brain interprets the signal as originating from the more commonly stimulated area, which is the shoulder or arm. This phenomenon is sometimes described as “crossed wires” in the nervous system, resulting in a deep, diffuse ache across the shoulder and arm.
Recognizing Accompanying Symptoms
Shoulder or arm pain resulting from a heart attack is rarely an isolated symptom and is often accompanied by other signs. The most common accompanying symptom is central chest discomfort, which may feel like uncomfortable pressure, squeezing, tightness, or fullness that lasts for more than a few minutes. This chest sensation may come and go, but the presence of other symptoms alongside it demands serious attention.
Other frequently reported symptoms include shortness of breath, which can occur with or without chest discomfort, and a sudden cold sweat. Individuals may also experience nausea, vomiting, lightheadedness, or unexplained dizziness. Pain radiating to the jaw, neck, or upper back are also common indicators that the discomfort is cardiac in origin.
Symptom presentation can vary significantly, especially in women, the elderly, and individuals with diabetes, who are more likely to experience “atypical” symptoms. For these groups, intense chest pain may be absent, with symptoms instead focusing on extreme fatigue, indigestion, or pain in the throat, jaw, or upper abdomen.
Immediate Steps and When to Seek Help
Any discomfort in the chest, shoulder, or arm that suggests a heart attack should be treated as an immediate medical emergency. The single most important step is to call 911 or your local emergency number immediately, rather than attempting to drive to the hospital. Prompt action is crucial because the amount of damage to the heart muscle is directly related to the time elapsed before treatment begins.
While awaiting emergency medical services, the individual should stop all activity and sit down to rest and try to remain calm. If there is no allergy and emergency services advise it, chewing a regular-strength aspirin (300mg) can be helpful, as it works to prevent further blood clotting, but always call for help first. If the person has nitroglycerin prescribed for a heart condition, they should take it as directed while waiting for help to arrive.
It can be difficult to distinguish cardiac pain from non-cardiac causes like muscle strain or arthritis. Unlike musculoskeletal pain, cardiac referred pain often presents with accompanying symptoms like sweating or shortness of breath, and it does not change with movement or rest of the shoulder. If there is any doubt about the source of the pain, always call emergency services, as delaying care can have serious, irreversible consequences.