This article reviews recent attempts to develop interventional procedures to treat certain prenatally detected fetal cardiac anomalies. No feasible prenatal interventions are available for the majority of major congenital heart defects. Over 20 years ago, it was observed that some forms of cardiac obstructive valve disease progressed in severity with fetal growth during gestation and therefore might be candidates for surgical intervention. Development of minimally invasive catheter techniques in children led to early attempts (1989–1992) at echocardiographic interventional techniques using a balloon or stent to open the aortic valve in fetal life and prevent the progression of cardiac obstructive valve disease. However, the results of prenatal valvuloplasty were poor, and the introduction of an alternative postnatal surgical approach (the Norwood procedure) for many patients led to abandonment of these efforts.
Attempts at prenatal valvuloplasty were abandoned for nearly 10 years, but were revisited in the early years of this century as a result of advances in catheter technology and experience with innovative catheter techniques. A program for prenatal intervention was started in 2000 at Boston Children’s Hospital. The primary focus of investigators at this hospital has been the treatment of critical aortic stenosis (AS), although they have also attempted treatment of both pulmonary valve and atrial septum obstruction in a smaller number of cases. Although there was technical success among the 70 patients reported after in utero treatment for AS, only 24% (17/70) achieved a biventricular repair. Despite the overall disappointing results of intervention for AS, the authors believe this work has led to modification of the techniques to improve the outcome and to improve the criteria for selection of suitable patients.
Prenatal intervention has also been investigated as possible treatment for 2 other fetal cardiac conditions, pulmonary valve obstruction and intact atrial septum. There is a less compelling rationale for balloon valvuloplasty on the right side of the heart during gestation. An alternative, postnatal balloon valvuloplasty, is usually successful in cases with patency of the pulmonary valve at birth. With respect to intact atrial septum, left ventricular outflow tract obstruction occurs in a subgroup of fetuses with the hypoplastic left heart syndrome (HLHS) or with critical AS. Using a balloon or stent to open and maintain patency of the atrial septum in such cases has proved technically challenging. In a study of 21 cases where an attempt was made to open the atrial septum, 10% of fetuses treated in utero died, and 42% of newborns died soon after birth.
Prenatal valvuloplasty is feasible for only a few, rare conditions. Candidates for intervention must fulfill strict selection criteria. These techniques remain experimental and will require convincing evidence of benefit before they become an accepted management option. At present, they should be performed only in the few dedicated centers with expert and experienced practitioners, including a fetal medicine specialist, an interventional cardiologist, and a fetal cardiologist.