The shape and function of the left ventricle in Ebstein's anomaly

Left ventricular (LV) failure is common in Ebstein's anomaly, though remains poorly understood. We investigated whether shape deformity impacts LV function.

Three-dimensional models of the right ventricle (RV) and LV from 29 adult Ebstein's patients and nine normal subjects were generated from cardiac magnetic resonance image tracings. LV end diastolic (ED) shape, systolic function, septal motion and ventricular interaction were analyzed.

LV ED volume index was normal in Ebstein's (75 ± 19 vs. 78 ± 11 ml/m(2) in normals, p=0.50) but the LV was basally narrowed and modestly dilated apically. LV function was reduced globally (ejection fraction (EF) 41 ± 7 vs. 57 ± 5% in normals, p<0.0001) and regionally (decreased mean segment displacement at end systole (ES) in 12/16 segments, basal Z-scores -2.1 to -1.0). Septal dyskinesis was suggested by outward mean segment displacement in at least one basal septal segment in 25 patients (86%) but refuted by septal thickening in 14 (48%), normal septal curvature at ED and ES, and by visually evident basal LV anterior translation in 27 patients (93%). LV EF correlated better with normalized tricuspid annular plane systolic excursion (r=0.70) than with RV EF (r=0.42) or RVEDVI (r=0.18).

Although the Ebstein's LV has preserved volume, it exhibits basal narrowing, modest apical dilation and global hypokinesis. The apparent basal septal dyskinesis observed in most patients is likely attributable to anterior cardiac translation rather than true paradoxical motion. LV EF is unaffected by RV volume, correlating well instead with RV longitudinal shortening.