Response to Letter Regarding Article, “Direction of Preoperative Shunting Affects Ventricular Mechanics After Tetralogy of Fallot Repair”

We thank Dr DeGroff for his comments on our study of ventric-ular mechanics during repair of tetralogy of Fallot.1 We acknowledge that the use of 2-dimensional echo sections to represent the 3-dimensional left ventricle (LV) is limiting. The degree of error introduced by this compromise is unknown in the absence of more comprehensive imaging. However, we believe that our conclusions are essentially correct. As noted, Matsumori et al2 defined limitations of a biplane Simpson rule for LV volume determination in the presence of right ventricular (RV) pressure and volume overload. A modified Simpson rule, including area planimetry of the LV short axis at 2 levels, was more accurate than a biplane model of the LV based on diameters and a prolate ellipsoid. Matsumori’s data also indicated that errors of echo algorithms versus angiography were qualitatively larger for RV volume overload, where septal distortion is greatest, than for R