Clinical follow-up All patients included will be followed-up at outpatients' clinic at 2 weeks, 1 month, 2 months post-hospital discharge and every 3 months thereafter (or earlier if symptomatic) up to a total of 18 months, given that the majority of clinical complications appear within this time frame.The composite clinical end-point will be poor response to NSAIDs treatment (defined by the need to switch to 2nd line therapy) and development of either recurrent, incessant or constrictive pericarditis.