Assessment of Ventricular Septal Defect Size and Morphology by Three-Dimensional Transthoracic Echocardiography

Background: Morphologic description of ventricular septal defect (VSD) is mandatory before performing the newly developed transcatheter closure procedure. Inaccurate estimation of defect size has been reported using conventional two-dimensional (2D) transthoracic echocardiography (TTE). The aim of this study was to assess VSD morphology and size using three-dimensional (3D) TTE compared with 2D TTE and surgery.

Methods: Forty-eight children aged 21.4 ± 29.3 months with isolated muscular (n = 11 [22.9%]) and membranous (n = 37 [77.1%]) VSDs were prospectively included. Three-dimensional images were acquired using full-volume single-beat mode. Minimal diameter, maximal diameter, and systolic and diastolic VSD areas were measured from 3D data sets using multiplanar reconstruction mode (QLAB 9). Maximal-to-minimal VSD diameter ratio was used to assess VSD geometry. Linear regression analysis and the Bland-Altman method were used to compare 3D measurements with 2D and surgical measurements in a subgroup of 15 patients who underwent surgical VSD closure.

Results: VSD 3D diameters and areas were measured in all patients (100%; 95% CI, 92.6%-100%). Maximal diameter was lower on 2D TTE compared with 3D TTE (7.3 vs 11.3 mm, P < .0001). Mean bias was 4 mm, with 95% of values ranging from -1.76 to 9.75 mm. Correlation between 3D maximal diameter and surgical diameter was strong (r(2) = 0.97, P < .0001), while correlation between maximal 2D diameter and surgical diameter was moderate (r(2) = 0.63, P < .0001). VSDs had an oval shape when assessed by 3D TTE. Maximal-to-minimal diameter ratio assessed by 3D TTE was significantly higher in muscular VSDs compared with membranous VSDs (3.20 ± 1.51 vs 2.13 ± 1.28, respectively, P = .01). VSD area variation throughout the cardiac cycle was 32% and was higher in muscular compared with membranous VSDs (49% vs 26%, P = .0001).

Conclusions: Three-dimensional TTE allows better VSD morphologic and maximal diameter assessment compared with 2D TTE. VSD shape and its changes during the cardiac cycle can be visually and quantitatively displayed. Three-dimensional echocardiography may thus be particularly useful before and during percutaneous VSD closure.