What is the most likely cause of left trapezius tenderness with chest discomfort radiating to the anterior and posterior arms in a 53‑year‑old woman when walking outdoors?

Acute Coronary Syndrome Until Proven Otherwise

In a 53-year-old woman presenting with left trapezius tenderness and chest discomfort radiating to both arms during exertion, acute coronary syndrome (ACS) is the most likely diagnosis and must be excluded immediately before attributing symptoms to musculoskeletal causes. 1

Why This Is Cardiac Until Proven Otherwise

• Radiation to both the anterior and posterior arms is a classic pattern for myocardial ischemia, substantially increasing the likelihood of ACS even when other features seem atypical. 1

• Women frequently present with atypical symptoms including sharp pain, throat discomfort, or isolated arm/shoulder pain rather than classic substernal pressure; approximately 13% of patients with sharp or pleuritic-type pain still have acute myocardial ischemia. 2, 1

• Exertional provocation (symptoms occurring when walking outdoors) is a hallmark of angina and strongly suggests myocardial ischemia rather than musculoskeletal pain. 2, 1

• Age 53 years places this patient in the high-risk category for coronary artery disease, mandating full cardiac evaluation regardless of atypical features. 1

• Trapezius pain can be an anginal equivalent; the ACC/AHA guidelines explicitly state that jaw, neck, shoulder, or arm discomfort without chest symptoms may represent ACS, especially when related to exertion. 2

Immediate Actions Required (First 10 Minutes)

• Obtain a 12-lead ECG within 10 minutes to detect ST-elevation, ST-depression, T-wave inversion, or other acute ischemic changes. 1

• Measure high-sensitivity cardiac troponin immediately; it is the most sensitive and specific biomarker for myocardial injury. 1

• Repeat troponin at 3–6 hours if the initial value is normal, because a single normal troponin drawn early may miss evolving injury; 30–40% of acute myocardial infarctions present with a normal or nondiagnostic initial ECG. 1

• Assess vital signs including heart rate, blood pressure in both arms, respiratory rate, and oxygen saturation to detect hemodynamic instability or pulse differentials. 1

High-Risk Features Requiring Emergency Transport

• If the ECG shows ST-elevation or new ischemic changes, activate emergency medical services immediately and manage as STEMI. 1

• If the patient exhibits diaphoresis, dyspnea, nausea, syncope, or hemodynamic instability, transport urgently to the emergency department by EMS—do not delay for office-based troponin testing. 1

Why Musculoskeletal Causes Are Less Likely

• Musculoskeletal chest pain typically worsens with specific movements (turning, twisting, bending, arm elevation) and is reproducible with palpation of the costochondral joints or chest wall. 2, 1

• Exertional provocation is atypical for costochondritis; musculoskeletal pain is usually positional or movement-related rather than triggered by walking outdoors. 3

• Bilateral arm radiation is uncommon in trapezius myalgia, which typically produces localized neck/shoulder tenderness without radiation to the anterior arms. 4, 5

• Even when chest-wall tenderness is present, up to 7% of patients still have ACS; reproducible tenderness does not exclude cardiac disease. 1

Alternative Life-Threatening Diagnoses to Consider

• Pulmonary embolism presents with acute dyspnea and pleuritic chest pain; tachycardia occurs in >90% of patients. 1

• Aortic dissection is characterized by sudden "ripping" or "tearing" pain radiating to the back, with pulse or blood-pressure differentials between arms. 1

• Pericarditis produces sharp, pleuritic chest pain that worsens when lying supine and improves when leaning forward, often with a friction rub. 1

Critical Pitfalls to Avoid

• Do not dismiss ACS in women based on atypical presentations; women are at higher risk for under-diagnosis and frequently present with sharp, stabbing, or isolated arm pain. 2, 1

• Do not assume a normal physical examination excludes ACS; uncomplicated myocardial infarction can present with entirely normal findings. 1

• Do not rely on nitroglycerin response to differentiate cardiac from non-cardiac chest pain, as esophageal spasm and other conditions may also respond. 1

• Do not attribute exertional symptoms to musculoskeletal causes without completing a full cardiac work-up; exertional provocation is the hallmark of angina. 2, 1

Management Algorithm

1. Obtain ECG within 10 minutes and measure high-sensitivity troponin immediately. 1

2. If ECG shows STEMI or new ischemic changes OR troponin is elevated, activate emergency services for immediate transport to the emergency department. 1

3. If ECG and initial troponin are normal, repeat troponin at 3–6 hours. 1

4. If both troponins are normal, the patient is low-risk for ACS but still requires outpatient stress testing or coronary CT angiography within 72 hours given age and exertional symptoms. 1

5. Only after ACS is definitively excluded should musculoskeletal causes be considered; palpate the trapezius and costochondral junctions for reproducible tenderness. 1, 3