Simple approach to quantitation of pericardial volumes
Authors: Kane A , Luis A S , Geske J B , Kane C J , Thaden J J , Michelena H I , Nkomo V T , Kane G C , Sinak L J , Pislaru S V 
Published: January 2025

Abstract

Background
Transthoracic echocardiography is the primary modality used for the assessment of the pericardial space. Guidelines recommend semi-qualitative assessment of the size of a pericardial effusion with characterization as trace, small, moderate or large. The reproducibility and association of this characterization is variable. Whether simple 2D-based quantitative measures of effusion size better associate with pericardial volumes is unclear. An accurate measure of pericardial volume would be helpful for tracking patients over time.

Purpose
To test whether 2D-based measures of the pericardial space could accurately predict pericardial volumes.

Methods
We retrospectively assessed a series of echos performed immediately prior to pericardiocentesis. 2D-based area tracings from the parasternal long and short axis at the papillary muscle level as well as 2D volumetric tracings from the apical 4 chamber view using the Simpson's method were tested with the operator blinded to the true pericardial volume (recorded at pericardiocentesis). Patients who underwent pericardiocentesis in setting of acute perforation were excluded as were patients where pericardiocentesis was unsuccessful or incomplete. Pericardial fluid area or volume was calculated by taking the difference between the measures obtained by tracing the epicardial border of the heart and pericardium (figure 1).

Results
The median pericardiocentesis (n=118) fluid volume was 500 mL (IQR 350 – 750 mL) with a range, 95–2300 mL. The pericardial fluid was serous (22%), sero-sanguineous (37%) and sanguineous in 41%. The effusion was malignant in 24 cases and due to inflammation in 42 cases. Pericardial area traces from either the parasternal short (r=0.56, p&lt;.0001) or long axis (r=0.62, p&lt;.0001) correlated modestly with measured pericardial volume. The average volume estimated echocardiographically by the Simpson’s method was 580 ± 359 mL (range, 85.8–2419 mL). There was stronger linear correlation between echocardiographic (apical 4-chamber measurement) and pericardiocentesis-derived volumes (r=0.92, p &lt; 0.0001; figure 2A). Etiology of the pericardial effusion was not associated with estimates of pericardial volumes. There was a large overlap in pericardial volume amongst the reading physician qualitative grading of effusion size (figure 2B). Categorization of pericardial effusion size was improved when based on volumetric estimates (Kappa 0.65) rather than physician estimates (Kappa 0.32; Figure 2B). Variation between measured pericardial volume and actual pericardial volume was most related to the quality of the image and the likely extent to which the pericardial fluid was not entirely captured in the image window.

Conclusion
Two-dimensional transthoracic echocardiography using biplane Simpson’s method of disks can simply and reasonably accurately estimate the pericardial effusion volume. This technique may add value in the serial assessment of pericardial effusions.

Figure 2