3-DIMENSIONAL ECHOCARDIOGRAPHIC MEASUREMENT OF LEFT-VENTRICULAR VOLUME IN-VITRO - COMPARISON WITH 2-DIMENSIONAL ECHOCARDIOGRAPHY AND CINEVENTRICULOGRAPHY

Objectives. This study was designed to compare three dimensional echoc ardiography, two dimensional echocardiography and cineventriculography for the purpose of measuring left ventricular volume in vitro. Backgr ound. Three dimensional echocardiographic systems have been shown to b e highly accurate in measuring the volumes of balloon phantoms. Howeve r, three-dimensional techniques have not been compared with standard t wo dimensional echocardiography in vitro or with cineventriculography, the clinical standard for left ventricular volume measurement. Method s. Excised porcine hearts were prepared with an internal latex sheath that could be filled and maintained with a known (''true'') volume of liquid. Each heart was then imaged by cineventriculography, standard t wo dimensional echocardiography and three dimensional echocardiography . Left ventricular volumes were calculated from 15 hearts at 25 volume s ranging from 50 to 280 ml by the following methods: 1) biplane cinev entriculography using the area length method; 2) two dimensional echoc ardiography by the apical biplane method using a summation of discs al gorithm in 15 cases and the single plane, four-chamber method using a summation of discs algorithm in 10 cases; and 3) three dimensional ech ocardiography using a polyhedral surface reconstruction volume computa tion algorithm based on multiple nonparallel, nonevenly spaced short a xis cross sections. Results. Results were compared with true volume, a nd a nonparametric analysis of variance was performed. Both measuremen t bias (systematic error) and imprecision (random error) were assessed . Ah methods tended to underestimate the true volume (two dimensional echocardiography -6.1 +/- 17.6%, three dimensional echocardiography -4 .7 +/- 5.0% and biplane cineventriculography -3.9 +/- 8.2%), although differences were not significant. Although there was a significant cor relation between the magnitude of measurement bias and the size of the volume being measured for two dimensional echocardiography and cineve ntriculography, the bias of three dimensional echocardiography was fai rly constant over the range of volumes. When bias was accounted for, t wo dimensional echocardiography was significantly less precise than ci neventriculography and three-dimensional echocardiography in terms of percent error (15.3 +/- 11.9%, 5.6 +/- 5.7% and 3.9 +/- 3.4%, respecti vely). Conclusions. Three dimensional echocardiography using a polyhed ral surface reconstruction algorithm for volume computation provides a ccuracy comparable to that of biplane cineventriculography in this in vitro model. Standard two-dimensional echocardiographic volume computa tion is significantly less accurate than the other two methods.