Introduction: Infants with CDH commonly require ECMO because of PHT. The degree to which these elevated pressures resolve is uncertain. The purpose of this study was to determine the persistence and clinical significance of PHT in this population beyond the neonatal period.Methods: 21 ECMO/CDH survivors (age 3.2 ± 1.4 yrs) were prospectively studied using an ECG and Doppler Echocardiogram (ECHO) to screen for the presence of PHT. 20 non-ECMO, non-CDH children (age 3.8 ± 2.2 yrs) without heart disease or suspicion of PHT were used as controls. The following Doppler measurements, corrected for heart rate, were made: pre-ejection period (PEP), acceleration time (AT) and ejection time (ET). Published standards define PHT as PEP/AT≥0.80 or AT/ET≤0.30 in the absence of measurable tricuspid regurgitation. An exercise/oxygen desaturation study was done on the CDH patients older than 3 yrs (n=12).Results: 8 of the 21 patients (38%) had evidence of PHT based on ECHO measurements, fulfilling both PHT criteria. One patient (5%) had evidence of PHT, fulfilling one PHT criterion. Mean ± SD values are listed below. No differences were found between the CDH groups with regard to sex, age, initial disease severity, length of ECMO run or later morbidity. There was no correlation between RVH on ECG and PHT by ECHO. 7/9 patients with PHT underwent the exercise/desaturation study (2 pts. were too young to be tested). 2/7 (29%) desaturated 5% or greater from baseline.Conclusion: PHT persists in a significant proportion of the ECMO/CDH population beyond the neonatal period. ECG is not a sensitive method to identify these patients. Intermittent hypoxemia may play a role in the slow resolution of PHT, but its clinical significance is uncertain. Serial testing is needed to determine the natural history of PHT and to decide if other evaluations (i.e., catheterizations) and/or interventions (i.e., medications) are warranted. Table

Table 1
Full size table