Session S21.3

Real-Time 3D Echocardiographic Quantification of Left Ventricular Volumes: Multicenter Study for Validation with Magnetic Resonance Imaging

V Mor-Avi*, C Jenkins, H Kühl, HJ Nesser, TH Marwick, A Franke, C Ebner,
B Freed, R Steringer-Mascherbauer, J Niel, L Sugeng, RM Lang

University of Chicago
Chicago, IL, USA

Background: Real-time 3D echocardiographic (RT3DE) evaluation of left ventricular (LV) volumes is more reproducible and accurate than the conventional 2D and M-mode techniques when compared to cardiac magnetic resonance (CMR) standard, as demonstrated in several single-center studies. Nevertheless, RT3DE-derived LV volumes were recently reported to be underestimated compared to CMR. Accordingly, we sought to study: (1) the accuracy and reproducibility of this technique in a multicenter setting, (2) the inter-institutional differences in these variables in relationship with investigators’ specific experience, and (3) potential sources of volume underestimation.
Methods: We studied 92 patients who underwent CMR and RT3DE imaging on the same day at 4 different institutions. All images were analyzed to obtain end-systolic and end-diastolic LV volumes (EDV, ESV). Repeated analyses were performed to determine the reproducibility of RT3DE and CMR. The investigation of potential sources of error included: (1) phantom imaging, (2) analysis-related differences, and (3) inter-modality differences in LV boundary estimates, such as inclusion of endocardial trabeculae and mitral valve plane in the LV volume.
Results: RT3DE-derived LV volumes correlated highly with CMR values (EDV: r=0.91; ESV r=0.93), but were 29 and 26% lower. This finding was consistent across participating institutions, with the magnitude of bias being directly related to the level of experience (2 to 3-fold differences). The reproducibility of RT3DE measurements was lower (4-13%) than that of CMR (4-7%). Minimal changes in endocardial surface position (1 mm) resulted in significant differences in measured volumes (11%). While analysis-related differences were proved negligible, exclusion of trabeculae and mitral valve plane from the CMR reference essentially eliminated the inter-modality bias.
Conclusion: RT3DE-derived LV volumes are underestimated in most patients because RT3DE imaging cannot differentiate between the myocardium and trabeculae. To minimize this difference, tracing the endocardium to include trabeculae in the LV cavity is recommended.

(Abstract Control Number: 276)