Quantitation of Pericardial Fluid Volume: Volumetric Estimation Compared with Guideline-Based Linear Grading

The aim of this study was to compare guideline-based linear and two-dimensional echocardiographic measures against drained pericardial fluid volume in patients undergoing pericardiocentesis and determine whether volumetric quantification improves accuracy and categorical grading of pericardial effusion size.

We retrospectively studied 245 adults who underwent transthoracic echocardiography immediately before complete pericardiocentesis. Blinded measurements included (1) maximal end-diastolic effusion thickness, (2) parasternal long-axis and (3) short-axis effusion area (pericardial silhouette minus cardiac silhouette), and (4) apical 4-chamber Simpson's volumetric estimation of pericardial space volume (pericardial minus epicardial tracings). Complete drained fluid volume served as the reference standard. Median drained volume was 500 mL (range, 50-4,300), and 76.7% had tamponade. Linear thickness correlated modestly with drained volume (R² = 0.484; root mean squared error [RMSE] 353 mL). Parasternal area-based methods performed similarly (R² = 0.53-0.58; RMSE, 318-334 mL). In contrast, Simpson's apical 4-chamber volumetric estimation showed stronger agreement (R² = 0.88; RMSE = 172 mL; concordance correlation coefficient, 0.94) with minimal bias (mean bias, -14 mL; 95% limits of agreement, -373 to 344 mL). Volumetric categorization improved agreement versus linear grading (κ 0.695 vs 0.293) and increased overall accuracy (80.4% vs 49.4%).

Guideline-suggested linear grading of pericardial effusion size demonstrates substantial imprecision. A simple apical 4-chamber Simpson's volumetric approach is more accurate and provides better categorical classification, supporting its use to enhance communication and serial follow-up.