This patient has classic acute pericarditis : pleuritic chest pain relieved by sitting forward, a pericardial friction rub, diffuse ST-segment elevation with PR depression on ECG, and a small pericardial effusion on echocardiogram. MCCQE objectives emphasize recognizing the characteristic clinical and ECG features that distinguish pericarditis from myocardial infarction (diffuse ST elevation rather than territorial changes).

First-line treatment for uncomplicated acute pericarditis is high-dose nonsteroidal anti-inflammatory therapy , such as acetylsalicylic acid (ASA) or ibuprofen, often combined with colchicine to reduce recurrence risk. ASA is particularly appropriate when ischemia is in the differential diagnosis.

Apixaban (anticoagulation) is not indicated and may worsen effusion. Pericardiocentesis is reserved for large effusions or cardiac tamponade. Levofloxacin is unnecessary without evidence of bacterial infection. Beta-blockers such as metoprolol do not treat pericardial inflammation.

Thus, high-dose acetylsalicylic acid is the most appropriate initial management for uncomplicated acute pericarditis.