Subacute pericardial tamponade can present without signs of cardiogenic shock. Symptoms and signs lack both sensitivity and specificity. METHODS:: We conducted a case-control study in consecutive hospitalized patients with moderate-to-large pericardial effusion who had no evidence of hemodynamic compromise upon admission. Patients with pericardial effusion drained for diagnostic and/or therapeutic purposes served as cases, and patients who were not drained served as controls. Demographic, clinical, and laboratory data were obtained by retrospective chart review. Echocardiograms were reviewed by 2 independent observers. Pericardial effusion scoring index was calculated for each patient based on effusion size, echocardiographic assessment of hemodynamics, and clinical factors. RESULTS:: A total of 48 patients were included in the study: 27(56%) patients had pericardial effusion drained and 21(44%) had clinical follow-up without drainage. Pericardial effusion drainage was surgical in 60% of the cases with the mean time to drainage of 2.5 days. No significant difference was seen between the groups in terms of clinical hemodynamic parameters such as blood pressure or heart rate upon initial presentation. The mean pericardial effusion scoring index was 6.0 for cases and 3.3 for controls showing a wide separation between the groups (P < 0.01). The area under the curve for receiver operator characteristic was 0.91 (95% confidence interval, 0.82-1.00). CONCLUSIONS:: The pericardial effusion scoring index obtained at the initial presentation in patients without immediate hemodynamic compromise showed a high accuracy in identifying patients who required pericardial effusion drainage downstream.