Clinical significance of pleural effusions and association with outcome in patients hospitalized with a first episode of acute pericarditis

The clinical significance of pleural effusions (PLEs) in the setting of acute pericarditis remains poorly investigated. We sought to identify predictive factors for PLEs and their association with the short- and long-term prognosis of patients with acute pericarditis. We enrolled 177 patients hospitalized with a first episode of acute pericarditis. In all cases an extensive clinical, biochemical, and diagnostic work-up to detect PLEs and establish etiological diagnosis was performed. All patients included were prospectively followed for a maximum of 18 months (median 12, range 1-18) and complications were recorded. PLEs were detected in n = 94 cases (53.1% of the cohort; bilateral 53.2%, left-sided 28.7%, right-sided 18.1%) and were strongly associated with c-reactive protein (CRP) levels at admission (rho = 0.328, p < 0.001). In multivariate logistic regression, independent predictors for PLEs were female gender (OR = 2.46, 95% CI 1.03-5.83), age (per 1-year increment OR = 1.030, 95% CI 1.005-1.056), CRP levels (per 1 mg/L increment OR = 1.012, 95% CI 1.006-1.019) and size of pericardial effusion (per 1 cm increment, OR = 1.899, 95% CI 1.228-2.935). Bilateral PLEs were associated with increased risk for in-hospital cardiac tamponade (OR = 7.52, 95% CI 2.16-26.21). There was no association of PLEs with new onset atrial fibrillation or pericarditis recurrence during long-term follow-up (χ² = 0.003, p = 0.958). We conclude that PLEs are common in patients hospitalized with a first episode of acute pericarditis. They are related to the intensity of inflammatory reaction, and they should not be considered necessarily as a marker of secondary etiology. Bilateral PLEs are associated with increased risk of in-hospital cardiac tamponade, but do not affect the long-term risk of pericarditis recurrence.