What are the appropriate diagnostic and treatment steps for a patient whose chest symptoms worsen when laying back?

Acute Pericarditis is the Most Likely Diagnosis

Sharp chest pain that worsens when lying supine and improves when sitting forward is pathognomonic for acute pericarditis, and this positional pattern should immediately direct your diagnostic workup toward this condition. 1

Immediate Life-Threatening Conditions to Exclude First

Before confirming pericarditis, you must rapidly rule out conditions that can kill the patient:

• Obtain a 12-lead ECG within 10 minutes to identify ST-segment elevation myocardial infarction, new left bundle branch block, or the widespread ST-elevation with PR depression characteristic of pericarditis 2, 1
• Measure cardiac troponin immediately upon presentation, as acute coronary syndrome can occasionally present with positional chest pain, particularly in women, elderly patients, and diabetics 2, 1
• Assess for aortic dissection red flags: sudden "ripping" pain radiating to the back, pulse differentials between extremities, or blood pressure differences >20 mmHg between arms 2, 3, 1
• Evaluate for pulmonary embolism: acute dyspnea, tachycardia >100 bpm, tachypnea, and pleuritic pain component 3, 1

Confirming Acute Pericarditis

Once life-threatening conditions are excluded, confirm pericarditis with these specific features:

Clinical Presentation

• Sharp, pleuritic chest pain that worsens when lying supine and improves when leaning forward is the hallmark positional pattern 2, 3, 1
• Pain may radiate to the trapezius ridge (a specific finding for pericarditis) 3
• Associated symptoms include fever and dyspnea 2, 3

Physical Examination

• Listen for a pericardial friction rub (biphasic or triphasic scratching sound), though it may be absent in up to 50% of cases 2, 3
• Assess for signs of cardiac tamponade: hypotension, jugular venous distension, muffled heart sounds 2, 3

Diagnostic Testing

• ECG shows widespread ST-elevation with PR depression (the classic pattern that distinguishes pericarditis from myocardial infarction, which has regional ST changes) 2, 3, 1
• Transthoracic echocardiography is recommended to determine presence of pericardial effusion, assess for tamponade physiology, and evaluate ventricular wall motion 2, 3
• Cardiac MRI with gadolinium is useful if diagnostic uncertainty exists or to determine the extent of pericardial inflammation, particularly when troponin is elevated suggesting myopericarditis 3

Critical Pitfalls to Avoid

• Do not use nitroglycerin response as a diagnostic criterion – esophageal spasm and other non-cardiac conditions also respond to nitroglycerin 2, 1
• Do not dismiss cardiac causes based on sharp or positional pain alone – approximately 7% of patients with reproducible chest wall pain still have acute coronary syndrome 3, 4
• Do not assume young age or atypical features exclude serious pathology – women, elderly, and diabetic patients frequently present with atypical symptoms including sharp or positional pain 2, 1
• Sharp chest pain that increases with inspiration and lying supine is unlikely related to ischemic heart disease, but you must still obtain ECG and troponin before safely ruling out cardiac causes 2, 4

Alternative Diagnoses with Positional Pain

If pericarditis is excluded, consider:

• Gastroesophageal reflux disease: worsens when lying flat due to increased acid reflux, with heartburn, regurgitation, relief with antacids, and worsening after meals or at night 1
• Costochondritis/Tietze syndrome: tenderness of costochondral joints on palpation, but typically worsens with specific movements rather than just lying flat 2, 3, 1
• Pneumonia: localized pleuritic pain, fever, productive cough, regional dullness to percussion, egophony, possible friction rub 2, 3, 1
• Pneumothorax: pleuritic pain on inspiration, unilateral absence of breath sounds, hyperresonant percussion 2, 3, 1

Transport Decision

• If any clinical evidence of acute coronary syndrome or life-threatening cause exists, activate 9-1-1 for EMS transport to the emergency department 2, 1
• In the office setting, do not delay transfer for troponin testing if acute coronary syndrome is suspected – transport urgently to ED by EMS 2, 4