The clinical syndrome of persistent pulmonary hypertension of the newborn (PPHN) still carries high mortality in spite of improved neonatal care. The purpose of this prospective study was to assess the utility of M-mode echocardiography for the early identification of infants with PPHN prior to clinical deterioration. Echocardiograms of 51 infants who needed fractional inspiratory oxygen (FIO2) ≥0.25 to maintain adequate Pao2 within 36 hours of life were compared to those of 115 healthy full-term and preterm newborns. Of the 51 infants, ten had elevated systolic time interval ratios of both ventricles simultaneously (ventricular pre-ejection period to ventricular ejection time [RPEP/RVET ≤0.50, LPEP/LVET ≤0.38J]). All of these newbrns had PPHN that was manifest clinically by 11 to 30 hours of age. The echocardiographic findings preceded clinical deterioration by at least one to five hours in all cases. The other 41 infants had clinical courses consistent with uncomplicated pulmonary disease. These data indicate that systolic time interval ratios, although not accurate measures of pulmonary arterial pressure and/or pulmonary vascular resistance, permit early identification of infants with PPHN and separation from others with uncomplicated pulmonary disease.
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