What emergency department workup and laboratory tests are indicated for a 17‑year‑old male with five nights of orthopnea, normal vital signs, normal sinus rhythm (NSR) with ST‑segment elevation on ECG, and a history of seasonal allergies treated with cetirizine?

Emergency Department Workup for 17-Year-Old with Orthopnea and ST Elevation

This 17-year-old male with orthopnea and ST elevation on ECG most likely has acute pericarditis or early repolarization pattern, and requires immediate cardiac troponin measurement, echocardiography, and inflammatory markers to differentiate between these diagnoses and rule out myocardial injury. 1, 2

Immediate ECG Interpretation

The ST elevation with normally inflected T waves in a young male with normal vital signs suggests either:

• Early repolarization pattern (most common in young Black males, characterized by widespread J-point elevation with QRS slurring or notching and rapidly upsloping ST segments) 1, 2
• Acute pericarditis (diffuse ST elevation with PR depression, though PR changes may be subtle initially) 2
• Myocarditis (less common but critical to exclude given orthopnea) 2

The normal vital signs argue strongly against acute coronary syndrome, pulmonary embolism, or other immediately life-threatening conditions. 1

Essential Laboratory Workup

Cardiac Biomarkers (Highest Priority)

• High-sensitivity cardiac troponin at presentation (0-hour) and repeat at 3 hours if initial is elevated 1, 3
  • Troponin elevation indicates myocardial injury and helps differentiate myopericarditis from isolated pericarditis 1
  • Even with ST elevation, troponin may be normal in early repolarization or isolated pericarditis 2

Inflammatory Markers

• Complete blood count with differential to assess for leukocytosis suggesting infection or inflammation 3
• C-reactive protein (CRP) and erythromycin sedimentation rate (ESR) to identify inflammatory process consistent with pericarditis 3

Additional Critical Labs

• Basic metabolic panel including potassium and calcium, as hyperkalemia produces prominent J-point elevation with peaked T waves that can mimic ST elevation 2
• Thyroid-stimulating hormone (TSH) to exclude thyrotoxicosis as a cause of orthopnea and tachycardia 3
• D-dimer only if clinical suspicion for pulmonary embolism exists (though PE typically presents with tachycardia and hypoxia, not present here) 4

Immediate Diagnostic Imaging

Transthoracic Echocardiography (Critical)

• Perform urgently to assess for pericardial effusion, regional wall motion abnormalities, left ventricular function, and right ventricular function 3, 5
• Echocardiography is essential to detect structural causes of orthopnea including cardiomyopathy, cardiac masses, or valvular disease 4, 5
• Wall motion abnormalities would suggest myocarditis or ischemia despite young age 1

Chest X-Ray

• Evaluate for cardiomegaly, pulmonary edema, pneumonia, or other pulmonary pathology that could explain orthopnea 3

Critical Diagnostic Considerations

Comparing with Prior ECGs

Always obtain and compare with any prior ECGs if available, as this is the single most important step in interpreting ST elevation in young patients 2. Many young males have chronic early repolarization that is their baseline. 1, 2

Age and Gender-Specific ST Elevation Thresholds

The upper normal limit for J-point elevation in lead V2 for males under 40 years is 0.25-0.33 mV (2.5-3.3 mm), significantly higher than the 0.1 mV threshold used in older adults 1. This makes early repolarization the most likely diagnosis in this demographic. 1, 2

Orthopnea as a Key Clinical Feature

Five nights of orthopnea in a young patient with normal vital signs suggests:

• Pericarditis with early effusion (positional chest discomfort is classic) 2
• Myocarditis with early heart failure (orthopnea from elevated filling pressures) 2
• Functional/anxiety disorder (though less likely with objective ECG findings) 6

The absence of tachycardia, hypoxia, or hemodynamic instability makes acute coronary syndrome, massive pulmonary embolism, or severe heart failure unlikely. 1, 3

Common Pitfalls to Avoid

• Do not assume ST elevation equals myocardial infarction in young patients – early repolarization is far more common and requires no treatment 1, 2
• Do not dismiss symptoms because vital signs are normal – early pericarditis or myocarditis can present with normal hemodynamics initially 3
• Do not overlook the need for serial troponins – a single normal troponin does not exclude myocardial injury; repeat at 3 hours is essential if initial suspicion exists 1
• Do not delay echocardiography – it provides immediate diagnostic information that laboratory results cannot 3, 5

Disposition Algorithm

If troponin elevated OR echocardiogram shows pericardial effusion/wall motion abnormalities:

• Admit for cardiac monitoring and further evaluation 1, 3

If troponin normal at 0 and 3 hours AND echocardiogram normal AND inflammatory markers normal:

• Likely early repolarization pattern; consider discharge with cardiology follow-up 1, 2

If inflammatory markers elevated with normal troponin and no effusion:

• Likely isolated pericarditis; may treat as outpatient with NSAIDs and colchicine if low-risk 3