A 39-year-old male presents to the emergency department with sudden onset of pleuritic chest pain that worsens with a supine position and relieves with leaning forward. He has no significant medical history except for a recent upper respiratory tract infection. He is a chronic smoker but denies any alcohol use. His temperature is 38.1°C (100.6°F). Laboratory tests show elevated C-reactive protein. An ECG is obtained and shown below.

Which of the following is the most likely diagnosis?