In order to assess the left ventricular systolic function we studied by echo 14 pts (8M, 6F) with complete atrioventricular septal defect (AVSD) who had undergone surgical repair. Mean age was 20.30 +/- 24.63 months, with a follow-up of 52.85 +/- 19.11%; in 6 pts Down syndrome was associated. Particularly, we tried to determine whether the following factors might affect the post-operative left ventricular systolic function: a) Down syndrome; b) residual mild mitral regurgitation; c) age of the surgical repair; d) length of the follow-up. As load-independent indexes of contractility, the left ventricular end systolic stress (LVESS)-circumferential fibre shortening velocity normalized for heart rate (VCFc) relationship and the LVESS/end systolic volume index (ESVI) ratio were chosen. All pts showed normal (mean +/- 2 standard deviations) or slightly higher values of LVESS/VCFc relationship; significantly, the only two pts with lower values had later undergone surgical repair. LVESS/ESVI ratio confirmed an inverse relationship between systolic function and age of the surgical correction (r = -0.75); no other factors (Down syndrome, residual mild mitral regurgitation, length of the follow-up) showed a significant correlation with the post-operative left ventricular systolic function. In conclusion, in our limited population, the age of the surgical repair appears to be the main factor affecting the post surgical left ventricular systolic function in pts with complete AVSD.