Introduction: In this study, we assessed the adequacy of the two echocardiographic parameters representing the longitudinal systolic function of the ventricles, MAPSE &TAPSE, in perioperative monitoring. Aims: 1. The assessment of MAPSE and TAPSE during the early (4 weeks) postoperative period after surgical correction of congenital heart defects in infants, performed with CPB. 2. The verification of the hypothesis, that the significant decline of TAPSE observed in this period is not related to the global RV systolic dysfunction. For this reason, systolic function of the RV was additionally assessed with another echocardiographic parameter: RVFAC. Material and methods: Prospective study with 51 infants operated due to ASDII, VSD, AVSD and TOF. Four measurements of MAPSE,TAPSE and RVFAC were performed in the apical four-chamber projection. TAPSE and MAPSE were expressed as metric values and z-score; RV FAC values were expressed in percentages. Results: TAPSE uniformly declined in the first postoperative day down to 34.5% of the initial value (p <0.00001), then gradually increased: up to 42.9% and 52% respectively, remaining significantly lower than preoperatively (p <0.001). RV FAC: increased by 21% (p <0.01), then remained stable in consecutive examinations. MAPSE declined by 21% during the first postoperative day, but with promptly normalized completely. Conclusions: The movement of both AV valve annuli is subjected to different, not fully understood influences. The relatively slight decline of MAPSE makes this parameter suitable for the assessment of the postoperative LV systolic function. Deep, long-lasting decline of TAPSE, uniform in the whole group, does not permit to use this parameter and suggests the choice of another one, e.g. RVFAC.