Etiology of pericardial effusion requiring invasive drainage: nationwide study in Japan.

BACKGROUND: Pericardial effusion (PE) is a heterogeneous clinical condition arising from diverse cardiovascular and systemic disorders, ranging from incidental findings to life-threatening cardiac tamponade. Although its etiology has been examined in prior studies, most were limited to single-center cohorts with small sample sizes, and comprehensive nationwide data remain limited. OBJECTIVES: To clarify the etiologies and in-hospital outcomes of PE requiring invasive drainage using a nationwide Japanese administrative database. METHODS: We retrospectively analyzed hospitalized patients with PE who underwent pericardiocentesis or pericardiotomy between April 2021 and March 2022, using the Diagnosis Procedure Combination database. Etiologies were classified according to underlying disease, and in-hospital mortality was assessed across major etiological categories. RESULTS: A total of 3778 patients met the inclusion criteria. The most common etiologies were cardiac disease (30.5%), malignant disease (25.9%), and vascular disease (16.9%). Among cardiac causes, valvular disease (26.7%) and acute myocardial infarction (22.5%) were predominant. Lung cancer (53.8%) and malignant lymphoma (8.5%) were the leading malignant etiologies, while aortic dissection (66.8%) and aortic aneurysm (26.1%) were the common vascular causes. Patients with vascular diseases, particularly aortic dissection, exhibited the highest in-hospital mortality (42.5%). Acute myocardial infarction demonstrated the highest mortality among cardiac etiologies (47.7%). Idiopathic PE was rare, accounting for only 0.6% of cases. CONCLUSIONS: Cardiac, malignant, and vascular diseases are the predominant etiologies of pericardial effusion requiring invasive intervention. The findings underscore the high mortality associated with vascular and ischemic cardiac causes, highlighting the importance of risk stratification and decision-making in PE management.