Fetal aortic valvuloplasty is the most commonly performed cardiac procedure, accounting for 75 percent of cases reported by the International Fetal Cardiac Intervention Registry (MoonGrady, 2015). It is ofered for selected cases of critical aortic stenosis in which the left ventricle is either normal sized or dilated. he goal is to prevent progression to hypoplastic left heart and to permit postnatal biventricular repair (McElhinney, 2009). Under sonographic guidance, an I8-gauge cannula is inserted through uterus and fetal chest wall and into the left ventricle. Although the procedure is ideally performed percutaneouslythrough the maternal abdominal wall-laparotomy may be needed if the fetal position is unfavorable. The cannula tip is positioned in front of the stenotic aortic valve, and a 2.5-to 4.5-mm balloon catheter is then guided into the aortic annulus and inlated. Fetal bradycardia requiring treatment complicates a third of cases, and hemopericardium requiring drainage afects approximately 20 percent (Moon-Grady, 2015).
From the first 100 cases at Boston Children's Hospital, 85 children survived, 38 of whom achieved biventricular circulation (Freud, 2014). Despite these successes, the mortality rate and risk for neurodevelopmental impairment in childhood appear to be similar to cases treated with postnatal repair (Laraja, 2017; Moon-Grady, 2015).
Fetal atrial septostomy, also using a percutaneous balloon catheter, is ofered in select cases of hypoplastic left heart with an intact or highly restrictive interatrial septum. This condition has a postnatal mortality rate of nearly 80 percent (Glantz, 2007). In an efort to ensure patency, atrial septal stent placement has
TABLE 16-5. Components of the Ex-Utero Intrapartum Treatment (EXIT) Procedure
Comprehensive preoperative evaluation: specialized sonography, fetal echocardiography, magnetic resonance imaging,
Uterine relaxation with deep general anesthesia and tocolysis
Intraoperative sonography to confirm placental margin and fetal position and to visualize vessels at uterine entry Placement of stay-sutures followed by use of uterine stapling device to decrease uterine entry bleeding
Maintenance of uterine volume during the procedure via continuous amnioinfusion of warmed physiological solution to help prevent placental separation Delivery of the fetal head, neck, and upper torso to permit access as needed Fetal injection of intramuscular vecuronium, fentanyl, and atropine Fetal peripheral intravenous access, pulse oximeter, and cardiac ultrasound Following procedure, umbilical lines placed prior to cord clamping Uterotonic agents administered as needed
Data from Moldenhauer, 2013.
also been performed. Of37 cases of atrial septostomy, survival to hospital discharge was almost 50 percent (Moon-Grady, 2015).
Fetal pulmonary valvuloplasty has been ofered in cases of pulmonary atresia with intact interventricular septum to prevent development of hypoplastic right heart syndrome. Although success is achieved in approximately two thirds of cases, it is not yet clear whether outcomes are improved compared with standard postnatal repair (Arzt, 2011; McElhinney, 2010).