In an adult patient with pleuritic chest pain, ST‑segment elevation and Q‑waves on ECG, and a fever two weeks ago, what are the differential diagnoses?

Differential Diagnosis: Pleuritic Chest Pain with ST Elevation, Q Waves, and Recent Fever

In a patient presenting with pleuritic chest pain, ST-segment elevation, Q waves on ECG, and a history of fever two weeks prior, the primary differential diagnoses are acute pericarditis (likely post-infectious), myopericarditis with myocardial involvement, post-myocardial infarction pericarditis (Dressler's syndrome), and purulent bacterial pericarditis—with acute coronary syndrome requiring immediate exclusion despite the atypical pleuritic character. 1, 2

Immediate Life-Threatening Exclusions (First 10 Minutes)

Acute Coronary Syndrome

• Sharp or pleuritic chest pain does NOT exclude acute myocardial ischemia; approximately 13% of patients with pleuritic-type pain have acute myocardial ischemia. 3, 4
• Q waves on ECG indicate either prior myocardial infarction or evolving STEMI with significant transmural injury. 5, 6
• Obtain high-sensitivity cardiac troponin immediately; elevation confirms myocardial injury and distinguishes STEMI from isolated pericarditis. 1, 3
• A completely normal physical examination does NOT exclude uncomplicated myocardial infarction. 3, 4

ST-Elevation Myocardial Infarction vs. Pericarditis Pattern

• STEMI typically shows localized ST elevation in contiguous leads corresponding to a coronary territory, with reciprocal ST depression elsewhere. 5, 6
• Pericarditis demonstrates diffuse concave ST elevation across multiple leads with PR-segment depression (opposite to P-wave polarity), without reciprocal changes. 1, 5
• The presence of Q waves suggests either prior infarction or acute transmural injury, making STEMI a critical consideration. 5, 6

Primary Differential Diagnoses

1. Acute Pericarditis (Post-Infectious/Viral)

• Sharp, pleuritic chest pain that worsens when lying supine and improves when sitting forward is pathognomonic for pericarditis. 1, 3, 4
• A prodrome of fever, malaise, and myalgia two weeks prior strongly suggests viral or post-viral pericarditis. 1
• Pericardial friction rub may be present (though only in <30% of cases) and is highly specific when heard. 1, 4
• ECG shows widespread concave ST-segment elevation with PR-segment depression; these changes are due to epicardial inflammation since the parietal pericardium is electrically inert. 1, 5
• Elevation of inflammatory markers (CRP, ESR, white blood cell count) is common and supports the diagnosis. 1
• Transthoracic echocardiography may reveal pericardial effusion (present in only 60% of cases), but absence does NOT exclude pericarditis. 1

2. Myopericarditis (Pericarditis with Myocardial Involvement)

• When cardiac troponin is elevated (occurs in up to 50% of acute pericarditis cases), the diagnosis is myopericarditis, indicating myocardial involvement in the inflammatory process. 1
• Regional wall motion abnormalities may be present on echocardiography. 1
• Q waves on ECG in this context may represent focal myocardial injury from the inflammatory process. 1, 5
• Cardiac MRI with gadolinium contrast is recommended to delineate the extent of pericardial and myocardial inflammation and to differentiate from other causes. 1, 4

3. Post-Myocardial Infarction Syndrome (Dressler's Syndrome)

• Dressler's syndrome presents as delayed-onset pericarditis occurring weeks to months after myocardial infarction or cardiac surgery. 1, 7
• The patient's fever two weeks ago could represent either the initial MI or a preceding viral illness, followed by immune-mediated pericarditis. 1, 7
• Q waves would represent the prior infarction, while ST elevation reflects the subsequent pericardial inflammation. 5, 7
• Pleural effusion is common (46% of cases) and may accompany pericardial effusion. 4, 7
• This is classified as a pericardial injury syndrome with auto-reactive (autoimmune) pathogenesis. 1

4. Purulent Bacterial Pericarditis (Pneumococcal or Other)

• Purulent pericarditis secondary to pneumococcal pneumonia is rare but represents a lethal manifestation of invasive pneumococcal disease. 2
• Fever two weeks prior followed by pleuritic chest pain, ST elevation, and Q waves matches the presentation of pneumococcal pericarditis with myocardial involvement. 2
• Blood cultures positive for Streptococcus pneumoniae or other bacteria confirm the diagnosis. 2
• Pericardiocentesis reveals purulent exudate positive for bacterial antigen. 2
• CT chest may show pericardial effusion with heterogeneous thickening, prominent adhesions, and possible associated pneumonia. 2
• This diagnosis requires urgent pericardiocentesis and intravenous antibiotics to prevent mortality. 2

5. Pulmonary Embolism with Infarction

• Pulmonary embolism presents with acute dyspnea, pleuritic chest pain, tachycardia (>90% of cases), and tachypnea. 1, 3, 4, 8
• ST elevation can rarely occur in massive PE (typically in right precordial leads with right ventricular strain pattern). 1, 5
• However, Q waves are NOT typical of PE and make this diagnosis less likely. 5
• Assess for risk factors: recent surgery, immobilization, malignancy, or hormonal contraception. 1, 8

6. Pneumonia with Pleural Involvement

• Pneumonia presents with fever, localized pleuritic chest pain, productive cough, regional dullness to percussion, and egophony. 3, 9, 4
• Chest X-ray confirms consolidation; however, pneumonia does NOT cause ST elevation or Q waves on ECG. 9, 5
• Pneumonia can coexist with pericarditis (as in pneumococcal pericarditis). 2

Diagnostic Algorithm

Step 1: Immediate Cardiac Evaluation

• Obtain 12-lead ECG within 10 minutes to differentiate STEMI pattern (localized ST elevation with reciprocal changes) from pericarditis pattern (diffuse concave ST elevation with PR depression). 1, 3, 4
• Measure high-sensitivity cardiac troponin immediately; elevation indicates myocardial injury (STEMI or myopericarditis). 1, 3
• If troponin is elevated AND ECG shows localized ST elevation with Q waves in a coronary distribution, activate emergency services for STEMI protocol. 3, 4

Step 2: Assess for Pericarditis

• Evaluate pain characteristics: Does pain worsen when lying supine and improve when sitting forward? This is pathognomonic for pericarditis. 1, 3, 4
• Auscultate for pericardial friction rub (mono-, bi-, or triphasic); presence is highly specific for pericarditis. 1, 4
• Check inflammatory markers (CRP, ESR, white blood cell count); elevation supports pericarditis. 1

Step 3: Imaging

• Perform transthoracic echocardiography to detect pericardial effusion, assess for tamponade physiology, and evaluate for regional wall motion abnormalities. 1, 4
• Obtain chest X-ray to exclude pneumonia, pleural effusion, or pneumothorax. 1, 9, 4
• If diagnostic uncertainty persists or troponin is elevated, perform cardiac MRI with gadolinium to differentiate myopericarditis from other causes. 1, 4

Step 4: Rule Out Infectious Etiology

• Obtain blood cultures to exclude bacterial pericarditis (especially pneumococcal). 2
• If pericardial effusion is present, consider pericardiocentesis with fluid analysis (cell count, Gram stain, culture, bacterial antigen testing) to exclude purulent pericarditis. 2

Step 5: Risk Stratification

• If troponin is normal, ECG shows diffuse ST elevation with PR depression, and pain is positional, diagnose acute pericarditis and initiate anti-inflammatory therapy. 1, 4
• If troponin is elevated with pericarditis pattern, diagnose myopericarditis and admit for monitoring. 1
• If Q waves are present without acute ST elevation in a coronary distribution, consider prior MI with subsequent Dressler's syndrome. 1, 7

Critical Pitfalls to Avoid

• Do NOT dismiss acute coronary syndrome solely because chest pain is pleuritic; 13% of patients with pleuritic pain have acute myocardial ischemia. 3, 4
• Do NOT rely on nitroglycerin response to differentiate cardiac from pericardial pain; esophageal spasm and other conditions may also respond. 3, 4
• Do NOT assume a normal physical examination excludes myocardial infarction; uncomplicated MI can present with entirely normal findings. 3, 4
• Do NOT overlook purulent bacterial pericarditis in patients with recent fever and ST elevation; this is a lethal condition requiring urgent drainage and antibiotics. 2
• Do NOT delay troponin measurement; a single normal ECG does NOT exclude acute coronary syndrome, as 30-40% of acute MIs have a normal initial ECG. 3, 4