Understanding Referred Pain: Why Shoulder Pain Can Signal Heart Trouble

Most people assume shoulder pain means a pulled muscle, a stiff joint or sleeping in an awkward position. Usually, that's true. But sometimes, pain in the shoulder has nothing to do with the shoulder at all. It may be the body's way of signalling a problem in an internal organ, most importantly, the heart.

This phenomenon is called referred pain and understanding it can help you recognise when a seemingly simple ache might be a medical emergency.

What Is Referred Pain?

Referred pain is pain felt in one part of the body even though the source of the problem lies elsewhere. It happens because of the way our nervous system is wired.

Nerves from internal organs, such as the heart, lungs, liver, gallbladder and diaphragm, enter the spinal cord at the same levels as nerves from certain areas of the skin and muscles. When an organ sends pain signals, the brain sometimes can't tell exactly where they're coming from. It "misreads" them as pain in the body area that shares the same nerve pathway.

Because we experience pain in our skin and muscles far more often than in our organs, the brain tends to assign the pain to those familiar areas.

How the Heart Refers Pain to the Shoulder

The heart shares nerve pathways with the chest, left arm, shoulders, neck, jaw and upper back. When the heart muscle doesn't get enough oxygen, as happens during angina or a heart attack, pain signals travel along these shared pathways.

As a result, heart-related pain may be felt in:

• The centre or left side of the chest
• The left shoulder, and sometimes the right shoulder or both
• The left arm, often down the inner side
• The neck and jaw
• The upper back, between the shoulder blades
• The upper abdomen

In some people, particularly women, older adults and people with diabetes, chest pain may be mild or absent, and shoulder, arm, jaw or back pain may be the main symptom.

Heart-Related Shoulder Pain vs Musculoskeletal Pain

While only a medical evaluation can confirm the cause, some patterns can offer clues.

Shoulder Pain More Likely from Muscles or Joints

• Starts after a specific movement, injury or overuse
• Gets worse when moving the shoulder or pressing on a specific spot
• Improves with rest or changing position
• Accompanied by stiffness or reduced range of motion
• Feels sharp or localised
• Common with conditions like rotator cuff injury, frozen shoulder, arthritis and tendinitis

Shoulder Pain That May Be Heart-Related

• Comes on with physical exertion, stress, heavy meals or cold weather
• Doesn't change when you move the shoulder or press on it
• Feels like pressure, heaviness, squeezing, tightness or a dull ache rather than sharp pain
• Spreads to the chest, arm, neck, jaw or back
• Accompanied by other symptoms such as breathlessness, sweating, nausea or dizziness
• Improves with rest in the case of stable angina, but may not improve during a heart attack

Warning Signs of a Heart Attack

Seek emergency medical help immediately if shoulder pain comes with any of these:

• Chest pain, pressure, tightness or discomfort
• Pain spreading to the arms, back, neck, jaw or stomach
• Shortness of breath
• Cold sweat
• Nausea or vomiting
• Light-headedness or dizziness
• Unusual fatigue or weakness
• A sense of impending doom or anxiety

What to Do

• Call emergency services immediately; in India, dial 108 or 112
• Stop all activity and sit or lie down
• Loosen tight clothing
• If you are not allergic and a doctor has not advised against it, chewing a regular-dose aspirin may help, but follow emergency operator guidance
• Don't drive yourself to the hospital
• If the person collapses and isn't breathing normally, start CPR if trained

In a heart attack, early treatment to restore blood flow saves heart muscle and lives. Don't wait to "see if it passes."

Heart Symptoms Can Differ in Women

Women are more likely than men to experience less typical heart attack symptoms, including:

• Pain in the shoulder, upper back, neck or jaw
• Shortness of breath without chest pain
• Nausea, indigestion-like discomfort or vomiting
• Extreme fatigue
• Light-headedness

Because these symptoms can be mistaken for less serious conditions, women sometimes delay seeking help.

People With Diabetes May Feel Less Pain

Diabetes can damage nerves over time, reducing the ability to feel pain. People with diabetes may experience a "silent" heart attack with mild or unusual symptoms such as shoulder discomfort, breathlessness or fatigue.

Other Organs That Can Cause Referred Shoulder Pain

The heart isn't the only organ that can cause shoulder pain.

• Gallbladder: Gallstones or inflammation can cause pain in the right upper abdomen that spreads to the right shoulder or shoulder blade, often after fatty meals.
• Liver: Liver conditions can occasionally cause right shoulder discomfort.
• Lungs: Conditions such as pneumonia, pleurisy, pulmonary embolism or, rarely, lung tumours can cause shoulder or chest pain, often with breathing difficulty or cough.
• Diaphragm: Irritation of the diaphragm, such as from blood or air in the abdomen, can cause pain at the tip of the shoulder.
• Spleen: Injury to the spleen may cause pain in the left shoulder, known as Kehr's sign, and is a medical emergency.
• Ectopic pregnancy: In women of childbearing age, shoulder tip pain with abdominal pain and bleeding can indicate a ruptured ectopic pregnancy, also an emergency.
• Neck (cervical spine) problems: A pinched nerve in the neck can cause pain radiating to the shoulder and arm.

Who Is at Higher Risk of Heart Disease?

Pay extra attention to unexplained shoulder pain if you have:

• High blood pressure
• Diabetes
• High cholesterol
• A smoking habit
• Obesity or a sedentary lifestyle
• A family history of early heart disease
• Age over 45 for men and over 55 for women
• Chronic stress
• Previous heart problems

Indians tend to develop heart disease at a younger age than many other populations, so risk factors should be taken seriously even in the 30s and 40s.

How Doctors Find the Cause

To determine whether shoulder pain is related to the heart, doctors may recommend:

• ECG (electrocardiogram): Detects heart rhythm problems and signs of heart muscle damage
• Cardiac enzyme tests such as troponin: Detect heart muscle injury
• Echocardiogram: Ultrasound of the heart to assess its function
• Treadmill test (TMT) or stress test: Evaluates how the heart performs during exertion
• Coronary angiography: Examines the heart's arteries for blockages
• Chest X-ray, abdominal ultrasound or shoulder imaging: To look for other causes

Protect Your Heart

• Control blood pressure, blood sugar and cholesterol
• Quit smoking and tobacco
• Exercise regularly
• Eat a balanced diet with plenty of vegetables, fruits and whole grains
• Maintain a healthy weight
• Manage stress and sleep well
• Get regular health check-ups, especially after 40

Conclusion

Shoulder pain is usually a musculoskeletal problem, but it can sometimes be a warning from the heart or another internal organ. Pay attention to how the pain starts, what makes it better or worse, and whether it's accompanied by other symptoms. When in doubt, especially if you have heart risk factors, seek medical care without delay.

If you've been experiencing unexplained shoulder, arm or jaw pain, a heart evaluation can give you peace of mind. Book your test with Citizens Specialty Hospital for an ECG and complete cardiac assessment.