Three-Dimensional Echocardiography: Rational Mode of Component Images for Left Ventricular Volume Quantitation

Three-dimensional echocardiography (3DE) improves the accuracy of left ventricle (LV) volumetry compared with the two-dimensional echocardiography (2DE) approach because geometric assumptions in the algorithms may be eliminated. The relationship between accuracy of mode (short- versus long-axis planimetry) and the number of component images versus time required for analysis remains to be determined. Sixteen latex models simulating heterogeneously distorted (aneurysmatic) human LVs (56–303 ml; mean 182 ± 82 ml) were scanned from an ‘apical’ position (simultaneous 2DE and 3DE). For 3DE volumetry, the slice thickness was varied for the short (C-scan) and long axes (B-scan) in 5-mm steps between 1 and 25 mm. The mean differences (true-echocardiographic volumes) were 16.5 ± 44.3 ml in the 2DE approach (95% confidence intervals –27.8 to +60.8) and 0.6 ± 4.0 ml (short axis; 95% confidence intervals –3.4 to +4.6) as well as 2.1 ± 9.9 ml (long axis; 95% confidence intervals –7.8 to +12.0) in the 3DE approach (in both cases, the slice thickness was 1 mm). Above a slice thickness of 15 mm, the 95% confidence intervals increased steeply; in the short versus long axes, these were –6.5 to +8.5 versus –7.0 to +10.6 at 15 mm and –10.1 to +15.7 versus –11.3 to +10.9 at 20 mm. The intra-observer variance differed significantly (p < 0.001) only above 15 mm (short axis). Time required for analysis derived by measuring short-axis slice thicknesses of 1, 15, and 25 mm was 58 ± 16, 7 ± 2 and 3 ± 1 min, respectively. The most rational component image analysis for 3DE volumetry in the in vitro model uses short-axis slices with a thickness of 15 mm.