Final answer:
The best descriptor of pericarditis in a patient is pain that worsens with deep inspiration and is alleviated by sitting upright, as this type of pain is characteristic of pericardium inflammation.
Step-by-step explanation:
The assessment finding that would best describe a patient with pericarditis is pain worse with deep inspiration, relieved by sitting in an upright position. This type of chest pain is characteristic of pericarditis, an inflammation of the pericardium that surrounds the heart. The pain associated with pericarditis can also be described as sharp and may radiate to the neck, shoulders, or back. Pain from pericarditis is typically worse when lying flat and may improve when leaning forward or sitting up.