Correlation of patent ductus arteriosus shunting with plasma atrial natriuretic factor concentration in preterm infants with respiratory distress syndrome.

The concentration of plasma atrial natriuretic factor (ANF) and the mechanism for its secretion were investigated in 17 preterm infants with respiratory distress. Their mean gestational age was 29 wk and wt 1250 g. The infants were followed during the first week of life by sequential Doppler ultrasound studies. Ductal openness versus closure and amount of ductal flow were correlated with plasma ANF concentrations. In a subset of 10 infants, sequential Doppler color flow mapping was used to quantify the ductal flow. During the first 72 h, plasma ANF was high, 361 pg/mL; it decreased to 96 pg/mL by the end of the 1st wk. The ANF level was significantly higher when the ductus was open than closed (393 versus 123 pg/mL, p less than 0.05). In patients with open ductus and bidirectional foramen ovale shunting (n = 3) ANF was 567 pg/mL and in those with left-to-right shunt 355 pg/mL (n 15, NS). The left atrial size, i.e. the left atrial to aortic root ratio, correlated with the amount of ductal shunting (r = 0.63, p less than 0.01) and with ANF concentration (r = 0.46, p less than 0.02). The correlation of ANF values and the magnitude of left-to-right ductal shunting assessed by color flow mapping was highly significant (r = 0.66, p less than 0.001). In these patients, the elevation of ANF is reflective of ductal flow.