DISCUSSION
In this study, we demonstrate strong agreement between Tomtec Image Arena and VMS+ 3.0 for left ventricular and left atrial volumetric calculations from pediatric 3D DICOM datasets over a wide range of age and BSA. We provide formulas for linear, optimally curve-fitted, and log-log transformed regressions using both software algorithms, and the distribution parameters (average, standard deviations) for the indexed values from the optimal fit regression. This permits calculation of normal ranges and z-scores specific to the algorithms used. We also demonstrate excellent to good inter and intraobserver agreement for these techniques by intraclass correlation.
Three-dimensional echocardiographic imaging has emerged as a useful adjust to standard 2-dimensional echocardiography in volumetric measurement, and in some cases is promoted as the preferable method. Its main advantage is measurement of the atrial or ventricular chamber without reliance on geometric assumptions and (usually) only two 2D imaging planes. The replicability of 3DE volumetric measurement of the LV has been shown to be superior to 2D calculations and 3D LV volumes are more comparable to those derived from the gold standard, cardiac magnetic resonance imaging (CMR)5,6, 7,25,26,27. Therefore 3DE volumetric imaging is becoming an important tool in risk stratification, pre-procedural planning, and assessment of treatment in pediatric and adult cardiac populations. 3DE offers a relatively inexpensive and readily available tool at the bedside to assess cardiac chamber volumes and a viable alternative modality when CMR is not feasible or contraindicated.
Measurement of the LA volume has been increasingly recognized as an important component of echocardiographic analysis, with robust data showing prognostic importance in cardiac failure, as well as in assessment of progressive mitral valve disease. Assessment of the phases of LA function (reservoir, conduit and atrial contraction), while beyond the scope of this study, can be assessed with 3DE. Changes in these phases may provide useful early warnings of progressive disease before detectable LV diastolic function becomes apparent.
This study, to the best of our knowledge, is the first to compare TomTec to VMS software in measuring left cardiac chambers. Given that TomTec software has been previously validated against CMR in recently published multi-center studies in pediatrics; we provide in this study an alternative software algorithm to currently available software with comparable accuracy and efficiency in measuring left cardiac chambers using real time 3DE. Both algorithms performed particularly well in patients with smaller BSA compared to larger BSA. This could be in part due to higher spatial and temporal resolution images obtained in smaller children, and the smaller chest excursion during breathing, leading to fewer stitch artifacts. It was true despite the higher heart rates in younger children, and the benefits of older patient cooperation and ability to understand instruction for breath holding during multi-beat acquisitions. Tomtec LA and LV measurements were on average slightly higher than VMS measurements which should be considered when using the two software interchangeably.
In considering utility in clinical practice, both VMS+ 3.0 and Tomtec Image Arena have quick post processing times (VMS on average being slightly faster, Table 5) for both LV & LA with means between 1.5 - 2 minutes for VMS and 3 minutes for TomTec for each chamber. Our analysis time did not include the time required to import datasets into the offline software packages, which may be longer than the analysis time itself. Integration of 3DE analysis packages with general echocardiographic reporting software, allowing direct launch of the analysis, and automatic upload of the measurements obtained can help to streamline this process, and encourages routine usage of these tools. Direct measurement on echocardiographic imaging modalities can also facilitate this process for some workflows.