Echocardiography Provides a Reliable Estimate of Total Cardiac Volume for Pediatric Heart Transplantation

Abstract

Background: Donor-to-recipient size matching for heart transplantation typically involves comparing donor and recipient body weight; however, weight is not linearly related to cardiac size. Attention has shifted toward the use of computed tomography- (CT-) derived total cardiac volume (TCV), that is, CT-TCV, to compare donor and recipient heart organ size. At this time, TCV size matching is near impossible for most centers due to logistical limitations. To overcome this impediment, echocardiogram-derived TCV (ECHO-TCV) is an attractive, alternative option to estimate CT-TCV. The goal of this study is to test whether ECHO-TCV is an accurate and reliable surrogate for TCV measurement compared with the gold standard CT-TCV.

Methods: ECHO-TCV and CT-TCV were measured in a cohort spanning the neonatal to young adult age range with the intention to simulate the pediatric heart transplant donor pool. ECHO-TCV was measured using a modified Simpson's summation-of-discs method from the apical 4-chamber (A4C) view. The gold standard of CT-TCV was measured from CT scans using three-dimensional reconstruction software. The relationship between ECHO-TCV and CT-TCV was evaluated and compared with other anthropometric and image-based markers that may predict CT-TCV. Inter-rater reliability of ECHO-TCV was tested among 4 independent observers. Subanalyses were performed to identify imaging views and timing that enable greater accuracy of ECHO-TCV.

Results: Banked imaging data of 136 subjects with both echocardiogram and CT were identified. ECHO-TCV demonstrated a linear relationship to CT-TCV with a Pearson correlation coefficient of r = 0.96 (95% CI, 0.95-0.97; P < .0001) and mean absolute percent error of 8.6%. ECHO-TCV correlated most strongly with CT-TCV in the subset of subjects <4 years of age (n = 33; r = 0.98; 95% CI, 0.96-0.99; P < .0001). The single-score intraclass correlation coefficient across all 4 raters is 0.96 (interquartile range, 0.93-0.98). ECHO-TCV measured from a standard A4C view at end diastole with the atria in the plane of view had the strongest correlation to CT-TCV.

Conclusions: ECHO-TCV by the A4C view was found to be both an accurate and reliable alternative measurement of CT-TCV and is derived from readily available donor ECHO images. The ECHO-TCV findings in this study make the ECHO method an attractive means of direct donor-to-recipient TCV size matching in pediatric heart transplantation.

Keywords: Echocardiography; Pediatric heart transplantation; Total cardiac volume.