pericarditis occurs when the thin sac-like tissue surrounding the heart known as the pericardium becomes inflamed it can be caused by things like infection localized injury inflammatory disorders and post-cardiac injury syndrome a common symptom is chest pain that worsens in the supine position and improves when leaning forward ecg changes can include concave st elevation and pr depression in the majority of leads with reciprocal st depression and pr elevation in avr and v1