Effects of left-to-right ductus shunting on left ventricular output and cerebral blood flow velocity in 3-day-old preterm infants with and without severe lung disease.

The effects of early left-to-right ductus shunting on left ventricular output (LVO) and cerebral blood flow velocity (CBV) were investigated in 3-day-old preterm infants by means of two-dimensional Doppler and M-mode echocardiography. Nineteen infants required mechanical ventilation because of severe lung disease (group A), and 19 had mild or no lung disease (group B). Six infants in each group had predetermined Doppler and M-mode criteria of a hemodynamically significant left-to-right ductus shunt (hsPDA). In group A the LVO was similar in infants with and without hsPDA, but those with hsPDA had lower mean arterial pressure (p = 0.006) and lower mean systolic-diastolic CBV (p = 0.001) than those without hsPDA. In group B the presence of hsPDA was associated with a higher LVO (p = 0.002), whereas neither mean arterial pressure nor mean systolic-diastolic CBV differed significantly in infants with and without hsPDA. In infants without hsPDA, those in group A had higher LVO (p = 0.012), lower mean arterial pressure (p = 0.003), and lower estimated systemic vascular resistance (p = 0.004) than those in group B. These results indicate that severely ill preterm infants receiving mechanical ventilation are less able than spontaneously breathing infants to defend systemic pressures and cerebral perfusion through an increase of LVO when a large ductus shunt develops. Possible reasons include an elevated baseline LVO, caused by systemic vasodilation, and hence a low preload reserve.