Myopericarditis versus viral or idiopathic acute pericarditis

Objective: To investigate the relative incidence, clinical presentation and prognosis of myopericarditis among patients with idiopathic or viral acute pericarditis. Design: Prospective observational clinical cohort study. Setting: Two general hospitals from an urban area of 220 000 inhabitants. Patients: 274 consecutive cases of idiopathic or viral acute pericarditis between January 2001 and June 2005. Main outcome measures: Relative prevalence of myopericarditis. Clinical features at presentation including echocardiographic data (ejection fraction (EF), wall motion score index (WMSI)) and follow-up data at 12 months including complications, results of echocardiography, electrocardiography and treadmill testing. Results: Myopericarditis was recorded in 40/274 (14.6%) consecutive patients. At presentation, the following clinical features were independently associated with myopericarditis: arrhythmias (odds ratio (OR) = 17.6, 95% confidence interval (CI) 5.7 to 54.1; p<0.001), male gender (OR= 6.4, 95% CI 2.3 to 18.4; p = 0.01), age <40 years (OR= 6.1, 95% CI 2.2 to 16.9; p= 0.01), ST elevation (OR= 5.4, 95% CI 1.4 to 20.5; p = 0.013) and a recent febrile syndrome (OR = 2.8, 95% CI 1.1 to 7.7; p = 0.044). After 12 months' follow-up an increase of EF (basal EF 49.6 (5.1)% vs 12-month EF 59.1 (4.6)%; p, 0.001) and decrease of WMSI (basal WMSI 1.19 (0.27) vs 12-month WMSI 1.02 (0.09); p< 0.001) were recorded in patients with myopericarditis, with a normalisation of echocardiography, electrocardiography and treadmill testing in 98% of cases. Use of heparin or other anticoagulants (OR= 1.1, 95% CI 0.3 to 3.5; p = 0.918) and myopericarditis (OR = 2.3, 95% CI 0.7 to 7.6; p = 0.187) was not associated with an increased risk of cardiac tamponade or recurrences. Conclusions: Myopericarditis is relatively common and shows a benign evolution also in spontaneous cases not related to vaccination.