Fetal Endotracheal Occlusion (FETO) in the Resolution of Pulmonary Hypertension in Fetuses With Severe CDH

A Prospective Study on the Role of Fetal Endotracheal Occlusion (FETO) in the Resolution of Pulmonary Hypertension Among Fetuses With Severe Congenital Diaphragmatic Hernia

Congenital diaphragmatic hernia (CDH) occurs when the diaphragm fails to fully fuse and leaves a portal through which abdominal structures can migrate into the thorax. In the more severe cases, the abdominal structures remain in the thoracic cavity and compromise the development of the lungs. Infants born with this defect have a decreased capacity for gas exchange; mortality rates after birth have been reported between 40-60%. Now that CDH can be accurately diagnosed by mid-gestation, a number of strategies have been developed to repair the hernia and promote lung tissue development.

Fetal tracheal occlusion (FETO), using a fetoscopically delivered and removed balloon device, has been used to temporarily occlude the trachea and increase lung distension in CDH to allow the lungs to develop and has been shown to increase survival at birth. The role of FETO in the resolution of pulmonary hypertension in fetuses with severe left- and right- sided CDH remains unclear. Our recent observation that FETO is associated with a higher proportion of infants who resolve their pulmonary hypertension by the age of 1 year as compared with those who have not had FETO, is based on a retrospective cohort study, which, as with any such design, has some intrinsic limitations. Thus, a prospective cohort study that is appropriately powered to confirm or disprove this encouraging observation is needed. If our preliminary observation is confirmed, resolution of PH by the age of 1 year could be added to the benefits of the FETO procedure in severe left and right-sided CDH cases.

The investigators will perform 40 FETO procedures on fetuses diagnosed prenatally with severe right- or left-sided CDH, and outcome data will be compared with that of a control group of severe right- or left-sided CDH who will not undergo the FETO procedure because of medical or social issues. Because the prevalence of left-sided CDH is higher than right-side CDH, the investigators will perform 25 FETO procedures in left sided CDH and 15 in right-sided CDH, and these outcomes will be compared to a cohort of 40 non FETO cases.

Enrollment

Women carrying a fetus with severe CDH and a normal karyotype will undergo routine clinical evaluation. The fetus will be 28+0/7 to 31+6/7 weeks of gestational age and have severe CDH. These patients will have ultrasound and/or MRI evaluation to rule out other anomalies, calculation of the LHR from ultrasound measurements, calculation of observed/expected total lung volume and percentage of liver herniation from fetal MRI studies, echocardiography, and detailed obstetric/perinatal consultation. Patients who meet the eligibility criteria will be extensively counseled, and those who wish to participate will provide written, informed consent for the study.

Procedure

The procedure will be performed under spinal anesthesia or local anesthesia with intravenous sedation. The technique of fetal endoscopic tracheal occlusion has been described. Using standard technique, a cannula will be inserted into the amniotic cavity and a fetoscope or flexible operating endoscope will be passed through the cannula into the amniotic fluid. If, upon evaluation, the fetal trachea cannot be entered as described above, the uterus will be accessed through an incision in the belly (called a laparotomy). A laparotomy is a surgical technique tin which an incision is made in the abdomen. After the incision has been made, the uterus will be temporarily repositioned externally. The baby will then be accessed using the fetoscope and ultrasound, as described above. The laparotomy will only be performed if the baby cannot be reached and repositioned to a more favorable one by doing external maneuvers (called external version) for the FETO procedure.

The scope will be guided into the fetal larynx, and then through the fetal vocal cords with the aid of both direct vision through the scope and cross-sectional ultrasonographic visualization. A detachable latex balloon will be placed in the fetal trachea midway between the carina and the vocal cords. The balloon will be inflated with isosmotic contrast material so that it fills the fetal trachea.

Postoperative

The mothers will be discharged once stable. Serial measurements of sonographic lung volume and LHR will begin within 24-48 hours following surgery and continue weekly by targeted ultrasound evaluation. Amniotic fluid level and membrane status will also be monitored at weekly intervals. Comprehensive ultrasonography for fetal growth will be performed every four weeks (+/- 1 wk). All discharged patients will stay within 30 minutes of TCH to permit standardized postoperative management and emergent retrieval of the balloon in the event of preterm labor or premature rupture of membranes prior to the scheduled removal.

After the FETO surgery, prior to leaving the hospital, the mother will be given a medical alert bracelet identifying her as a patient with a baby with blocked airways. She will be encouraged to wear the bracelet at all times so that in case of emergency, she and others will know who to contact. She will also be given a pamphlet with instructions for medical personnel describing how to remove the balloon in case of an emergency. She should carry it with her at all times.

Balloon retrieval will be planned for no later than 36+6/7 weeks, at the discretion of the FETO center. The patient will need to commit to remaining in 30 minutes of Texas Children's Hospital Pavilion for Women until the balloon is retrieved. In the event of a patient relocating after having the balloon placed, despite having committed to remain in the area during consent process, she will be asked to return for the removal. Every effort to make arrangements for her to be managed by the nearest center capable of an EXIT procedure or balloon retrieval will be made.

After removal of the balloon, patients will have the choice of delivering at Texas Children's Hospital - Women's Pavilion with the CDH managed and repaired at TCH, or returning to their obstetrician for delivery with subsequent repair of the CDH by the pediatric surgeons at their referring facility. Given the severity of the CDH, the baby will need to be delivered in a facility that has the capability of immediate pediatric surgery services.

The investigators will need to monitor the baby at regular intervals (at 6 weeks, 3 months, 6 months, 1 year, and 2 years) after delivery to see how well the baby is breathing and how well the baby is developing. These check - ups may be at Texas Children's Hospital - Pavilion for Women or can be coordinated with doctors from the hospital of the participant's choosing.

If the child continues care at another institution, the investigators will attempt to follow up with a review of the child's medical records.

Inclusion Criteria:

• Patient is a pregnant woman between 18 and 45 years of age
• Singleton pregnancy
• The fetuses will be 28+0/7 to 31+6/7 weeks of gestational age
• Confirmed diagnosis of severe left- or right-sided CDH of the fetus: Observed/expected total lung volume equal to or less than 0.32 with more than 21% of liver herniated into the hemithorax. (Ideally calculated between 28+0/7 and 31+6/7 weeks' gestation.)
• Normal fetal echocardiogram or echocardiogram with a minor anomaly (such a small VSD) that in the opinion of the pediatric cardiologist will not affect postnatal outcome
• Normal fetal karyotype or microarray
• The mother must be healthy enough to have surgery
• Patient and father of the baby provide signed informed consent that details the maternal and fetal risks involved with the procedure
• Patient willing to remain in Houston for the duration following balloon placement until delivery.

Exclusion Criteria:

• Contraindication to abdominal surgery, fetoscopic surgery, or general anesthesia
• Allergy to latex
• Allergy or previous adverse reaction to a study medication specified in this protocol
• Preterm labor, preeclampsia, or uterine anomaly (e.g., large fibroid tumor) in the index pregnancy.
• Fetal aneuploidy, known structural genomic variants, other major fetal anomalies that may impact the fetal/neonatal survival or known syndromic mutation
• Suspicion of major recognized syndrome (e.g. Fryns syndrome) on ultrasound or MRI
• Maternal BMI >40
• High risk for fetal hemophilia