UNDERESTIMATION OF THE SEVERITY OF PULMONARY OUTFLOW TRACT OBSTRUCTION IN THE FIRST DAY OF LIFE - DOPPLER-ECHOCARDIOGRAPHIC STUDY

To find out whether there is an underestimated severity of narrowing i n obstructive lesions of the pulmonary outflow tract in the first day of life, Doppler measurement of the pulmonary outflow tract gradient a nd estimation of the pulmonary artery systolic pressure in 15 neonates with pulmonary outflow tract obstruction with a variety of associated lesions were studied in the first twenty-four hours of life (mean thi rteen hours, range six to twenty-four) and repeated at the age of twen ty-six to seventy-two hours (mean forty-nine). The maximal instantaneo us gradient across the pulmonary outflow tract obstruction (22.4 +/- 9 .0 mmHg) in the first day of life was significantly lower than at the repeated study (61.0 +/- 19.4 mmHg, (P < 0.001). In 12 patients with p atent ductus arteriosus, transductal gradient increased significantly at the repeated examination (19.6 +/- 9.3 vs 48.2 +/- 6.1 mmHg, P < 0. 001). The pulmonary outflow tract gradient in these 12 patients was 22 .3 +/- 8.4 vs 62.9 +/- 21.1 mmHg, (P < 0.001). The severity of the pul monary outflow tract obstruction was underestimated in the first twent y-four hours of life. Low gradient across pulmonary outflow tract and low transductal gradient in the first day of life mirrored high pulmon ary arterial systolic pressure. At the repeated study the increase in transductal gradient and the increase in the pulmonary outflow tract g radient more accurately represented the severity of pulmonary outflow tract obstruction owing to the decline in the systolic pulmonary arter ial pressure.