outcomes of idiopathic chronic large pericardial effusion objective aim of this paper is to evaluate the outcomes of idiopathic chronic large pericardial effusions without initial evidence of pericarditismethods all consecutive cases of idiopathic chronic large pericardial effusions evaluated from 2000 to 2015 in three italian tertiary referral centres for pericardial diseases were enrolled in a prospective cohort study the term idiopathic was applied to cases that performed a complete diagnostic evaluation to exclude a specific aetiology a clinical and echocardiographic followup was performed every 36 monthsresults 100 patients were included mean age 613146 years 54 females 44 patients were asymptomatic according to clinical evaluation with a mean followup of 50 months the baseline median size of the effusion evaluated as the largest enddiastolic echofree space was 25mm iqr 8 and decreased to a mean value of 7mm iqr 19 p00001 with complete regression in 39 patients at the end of followup there were no new aetiological diagnoses adverse events were respectively cardiac tamponade in 8 patients 80 pericardiocentesis in 30 patients 300 pericardial window in 12 cases 120 and pericardiectomy in 3 patients 30 recurrencefree survival and complicationsfree survival was better in patients treated without interventions log rank p00038conclusions the evolution of idiopathic chronic large pericardial effusions is usually benign with reduction of the size of the effusion in the majority of cases and regression in about 40 of cases the risk of cardiac tamponade is 22year and recurrencecomplications survival was better in patients treated conservatively without interventions