3-DIMENSIONAL ECHOCARDIOGRAPHY - IN-VIVO VALIDATION FOR RIGHT-VENTRICULAR FREE-WALL MASS AS AN INDEX OF HYPERTROPHY

Objectives. This study tested the ability of three dimensional echocar diography to reconstruct the right ventricular free wall and determine its mass in vivo using a system that automatically combines two dimen sional images with their spatial locations. Background. Right ventricu lar free wall thickness is limited as an index of right ventricular hy pertrophy because right ventricular mass may increase by dilation with out increased thickness and because trabeculations and oblique views c an exaggerate thickness in individual M mode and two dimensional scans . Three dimensional echocardiography may have potential advantages bec ause it can integrate the entire free wall mass, uninfluenced by obliq ue views or geometric assumptions. Methods. The three dimensional syst em was applied to 12 beating canine hearts to reconstruct the right ve ntricular free wall in intersecting views. The corresponding mass was compared with actual weights of the excised right ventricular free wal l (15.5 to 78 g), For comparison, right ventricular sinus and outflow tract thickness were also measured by two dimensional echocardiography , and the ability to predict mass from these values was determined. Re sults. The three dimensional algorithm successfully reproduced right v entricular free wall mass, which agreed well with actual values: y = 1 .04x + 0.02, r = 0.985, SEE = 2.7 g (5.7% of the mean value). The two dimensional predictions showed increased scatter: The variance of mass estimation, based on thickness, was 9.5 to 12.5 (average 11) times hi gher than the three dimensional method (p < 0.02). Conclusions. Despit e the irregular crescentic shape of the right ventricle, its free wall mass can be accurately measured by three dimensional echocardiography in vivo, providing closer agreement with actual mass than predictions based on wall thickness. This method, with the increased efficiency o f the three dimensional system, can potentially improve our ability to evaluate the presence and progression of right ventricular hypertroph y.