Dynamic adaptive changes in heart function first 10 days after birth in healthy term neonates

OBJECTIVE: Study heart function adaptations first ten days after birth in healthy term neonates. STUDY DESIGN: Prospective, observational study (n = 50). Mean (SD) gestational age 40.0 (1.1) weeks, birth weight 3.6 (0.4) kg. Serial assessment by speckle tracking echocardiography (STE), pulsed-wave tissue Doppler imaging (pwTDI) and conventional echocardiography at day one, three, and six-to-ten after birth. Linear mixed effects models to estimate heart function over time and impact from heart rate. RESULTS: Left ventricular global longitudinal strain (GLS) decreased from day one to six-to-ten (marginal means (SE) -18.6 (0.2) to -17.3 (0.2) %), strain rate was unchanged. Left pwTDI derived peak systolic velocity (s´), excursion and stroke volume exhibited a u-shaped pattern with significantly decreased values at day tree. Right ventricular longitudinal strain (-17.9 (0.3) to -19.7 (0.4) %), strain rate (-1.32 (0.03) to -1.59 (0.04) 1/s) and s´ (6.3 (0.2) to 7.1 (0.2) cm/s) increased from day one to six-to-ten. Between left and right ventricle, longitudinal strain, strain rate and s´ developed significantly different over time. Both left and right systolic strain rate increased with heart rate, (coefficient (SE)) 0.02 (0.01) and 0.04 (0.01) /s per 10 beats/min, respectively. CONCLUSIONS: Left ventricular systolic indexes decreased over the first three days and did not stabilize by day three. In contrast, right ventricular systolic indexes increased over time and the significant changes occurred mainly after day three. Time should be considered when evaluating heart function after birth. Underlying mechanisms probably involve loading conditions and adrenergic stimulation.