What is the differential diagnosis, initial evaluation, and management for right‑sided chest pain at the sixth intercostal space that worsens when supine and improves when sitting up, without dyspnea?

Right-Sided Chest Pain Worse Supine, Better Sitting: Differential Diagnosis and Management

This positional pattern—pain worsening when lying down and improving when sitting up—is atypical for classic pericarditis (which typically worsens supine and improves leaning forward), but acute coronary syndrome, pulmonary embolism, and musculoskeletal causes must all be excluded before attributing symptoms to a benign etiology.

Immediate Life-Threatening Exclusions (First 10 Minutes)

Mandatory Initial Testing

• Obtain a 12-lead ECG within 10 minutes to identify ST-elevation myocardial infarction, new ischemic changes, or pericarditis patterns (diffuse ST-elevation with PR-depression). 1
• Measure high-sensitivity cardiac troponin immediately because it is the most sensitive biomarker for myocardial injury, even when the presentation appears atypical. 1
• Assess vital signs bilaterally (heart rate, respiratory rate, oxygen saturation, blood pressure in both arms) to detect pulse differentials suggestive of aortic dissection or tachycardia/tachypnea indicating pulmonary embolism. 1

Why Cardiac Causes Cannot Be Dismissed

• Sharp or positional chest pain does NOT exclude acute coronary syndrome; approximately 13% of patients with pleuritic-type pain have acute myocardial ischemia. 1, 2
• A completely normal physical examination does NOT exclude myocardial infarction; uncomplicated MI can present with entirely normal findings. 1
• Right-sided chest pain can represent cardiac ischemia, particularly in women, elderly patients, and individuals with diabetes who frequently present with atypical symptoms. 1

Differential Diagnosis by Likelihood

1. Musculoskeletal (Costochondritis) – Most Likely if Cardiac Excluded

• Pain that worsens with chest-wall movement, deep breathing, turning, or twisting is characteristic of costochondritis. 3, 2
• Palpation-induced tenderness over the right 6th costochondral junction confirms the diagnosis. 3, 2
• Costochondritis accounts for approximately 43% of chest-pain presentations in primary care after cardiac causes are excluded. 3, 2
• Critical pitfall: Up to 7% of patients with reproducible chest-wall tenderness still have acute coronary syndrome, so ECG and troponin are mandatory before diagnosis. 3, 4

2. Atypical Pericarditis Presentation

• Classic pericarditis causes sharp, pleuritic pain that worsens supine and improves sitting forward, but atypical positional patterns can occur. 1, 2
• Look for a pericardial friction rub on auscultation (though absence does not exclude disease). 1
• ECG may show diffuse concave ST-elevation with PR-depression, distinguishing it from STEMI. 2
• Fever commonly accompanies pericarditis but may be absent early. 1

3. Pulmonary Embolism – Must Be Excluded

• Tachycardia occurs in >90% of PE patients, and dyspnea with pleuritic chest pain is the hallmark presentation. 1, 2
• Apply Wells criteria to estimate pre-test probability before ordering D-dimer or CT pulmonary angiography. 2
• Absence of dyspnea substantially reduces PE likelihood but does not eliminate it. 1

4. Pneumothorax

• Classic triad: dyspnea, pleuritic pain on inspiration, and unilateral absence of breath sounds with hyperresonant percussion. 1, 2
• Right-sided location at the 6th intercostal space is anatomically consistent with apical or lateral pneumothorax. 2

5. Esophageal Causes (GERD, Esophageal Spasm)

• Burning retrosternal pain related to meals or occurring at night, often relieved by antacids, suggests GERD. 3
• Esophageal spasm can mimic cardiac ischemia and may respond to nitroglycerin; therefore, nitroglycerin response should NOT be used to differentiate cardiac from esophageal pain. 1, 3

6. Pneumonia

• Fever with localized, often pleuritic chest pain; examination may reveal regional dullness, egophony, or a pleural friction rub. 1, 2
• Chest radiograph confirms diagnosis. 2

Algorithmic Management Pathway

Step 1: Immediate Risk Stratification (0–10 minutes)

1. Obtain 12-lead ECG within 10 minutes. 1
2. Measure high-sensitivity cardiac troponin immediately. 1
3. Perform focused cardiovascular examination for new murmurs, pericardial friction rub, unilateral absent breath sounds, pulse differentials, or hemodynamic instability. 1
4. Obtain chest radiograph to evaluate for pneumothorax, pneumonia, pleural effusion, or widened mediastinum. 2

Step 2: If High-Risk Features Present → Activate EMS Immediately

• ST-elevation or new ischemic changes on ECG → manage as STEMI. 1
• Hemodynamic instability, diaphoresis, dyspnea, nausea, or syncope → urgent transport to ED by EMS. 1
• Sudden "ripping" pain with pulse or blood-pressure differential >20 mm Hg between arms → activate aortic-dissection protocol. 1

Step 3: If Initial ECG and Troponin Normal

• Repeat troponin at 3–6 hours to reliably exclude myocardial injury. 1
• Attempt pain reproduction with palpation of the right 6th costochondral junction and with arm movement. 3, 4
• If pain is reproducible and both troponins are normal, diagnose costochondritis and prescribe NSAIDs (ibuprofen 600–800 mg three times daily for 1–2 weeks). 3

Step 4: If Pericarditis Suspected

• Look for widespread ST-elevation with PR-depression on ECG and pericardial friction rub. 1, 2
• Initiate high-dose aspirin (500 mg–1 g every 6–8 hours) plus colchicine (0.5–0.6 mg once or twice daily for 3 months) to reduce symptoms and prevent recurrence. 2
• Avoid glucocorticoids and non-aspirin NSAIDs because they may increase the risk of recurrent myocardial infarction. 2

Step 5: If PE Suspected (Tachycardia, Tachypnea, or Risk Factors)

• Calculate Wells score; if low-to-intermediate probability, obtain age- and sex-specific D-dimer. 2
• If high probability or positive D-dimer, proceed to CT pulmonary angiography. 2

Critical Pitfalls to Avoid

• Do NOT dismiss ACS solely because chest pain improves when lying down; the atypical positional pattern does not exclude life-threatening cardiac disease. 1
• Do NOT assume that reproducible chest-wall tenderness rules out ACS; approximately 7% of such patients still have acute coronary syndrome. 3, 4
• Do NOT rely on nitroglycerin response as a diagnostic criterion because esophageal spasm and other non-cardiac conditions may also improve. 1, 3
• Do NOT delay transfer to the emergency department for troponin testing in office settings; suspected ACS patients should be transported urgently by EMS. 1
• Do NOT assume absence of dyspnea completely excludes PE or pneumothorax; some patients present with isolated pleuritic pain. 1, 2

Special Populations Requiring Heightened Vigilance

• Women may present with throat discomfort, nausea, or fatigue rather than classic chest pressure; obtain ECG and troponin even with atypical features. 1
• Older adults (age >75 years) presenting with dyspnea, syncope, acute delirium, or unexplained fall need immediate cardiac evaluation. 1
• Patients with diabetes, chronic kidney disease, or dementia often have atypical presentations and warrant a full cardiac work-up. 1