Intraamniotic Fetal Echocardiography
A New Fetal Cardiovascular Monitoring Approach During Human Fetoscopic Surgery
A 33-year-old pregnant women had been referred to our center at 28+1 weeks’ gestation. Maternal transabdominal fetal ultrasound imaging at that time revealed a fetal congenital diaphragmatic hernia with very hypoplastic lungs. Because of the poor prognosis of the fetal congenital diaphragmatic hernia, temporary fetoscopic balloon occlusion was performed as a potentially live-saving experimental treatment approach. Fetoscopic tracheal balloon removal was scheduled at 32+5 weeks’ gestation. At that time, fetal ultrasound imaging was more difficult because of the more advanced gestational age in combination with severe adipositas (body mass index = 43 kg/m2) and polyhydramnios (Figure 1). Therefore, the feasibility of intraamniotic fetal echocardiography (IFE) was assessed as a more suitable monitoring tool. The fetoscopic and ultrasound-guided procedure was performed with parental informed consent and approval from the local committee of human research, in accordance with the ethical standards for human experimentation established by the Declaration of Helsinki.
The procedure was performed under general maternofetal anesthesia using desflurane and remifentantil. An 11-F catheter sheath was percutaneously placed into the amniotic cavity.1 Then, a 10-F single-plane intravascular ultrasound catheter (AcuNav, Acuson-A-Siemens-Company, Erlangen, Germany) was inserted via the catheter sheath into the amniotic cavity and placed against the fetal chest (Figure 2). The catheter was tipped with a frequency-agile 5.5- to 10-MHz vector phased-array ultrasound transducer that permits high-resolution 2-dimensional real-time imaging as well as multimodal Doppler imaging in a single plane that extends parallel to the long axis of the catheter into the lateral direction. Sound penetration ranged from 2 mm to about 10 cm from the lens.
IFE permitted substantially clearer definition of fetal cardiac anatomy, lung hyperechogenicity, and fetoplacental blood flow than conventional maternal transabdominal fetal echocardiography. A variety of nonstandard cardiac views were achieved from various intraamniotic positions that allowed good-quality 2-dimensional imaging of all cardiac chambers, semilunar and atrioventricular valves, and supra- and infracardiac vessels (Figures 2 and 3⇓). Color and pulsed Doppler imaging permitted assessment of fetal cardiovascular flows and fetoplacental circulation.
After IFE, fetoscopic guidance was used to destroy the tracheal balloon, and the catheter sheath was removed. Mother and fetus tolerated the procedure well, and complications were not observed. The fetus was electively delivered at 34+5 weeks’ gestation at the University of Mannheim, a center specializing in the treatment of infants with congenital diaphragmatic hernia.
These images prove the potential of IFE during fetoscopic surgery in a human fetus. The novel technique provides a useful cardiovascular monitoring tool during fetoscopic procedures when conventional maternal transabdominal assessment of fetal hemodynamics is severely impaired by unfavorable imaging conditions or when gas insufflation of the amniotic cavity is performed.1 Intraamniotic placement of the ultrasound catheter is performed via the same port through which the fetoscopic procedure is performed. The intraamniotic positioning of the imaging catheter helps avoid the problems of sound attenuation and scattering from the adipose maternal abdominal wall and also helps overcome the large distance to the fetus that has severely impaired maternal transabdominal fetal imaging.
Fetal IFE permits 2-dimensional as well as color Doppler and pulsed-wave Doppler studies of the fetal heart and fetoplacental circulation from within the amniotic cavity. Because standard views (eg, 4-chamber view, short-axis view, aortic arch view, ductal arch view) may not be obtained by this technique, the intraamniotic imaging approach requires advanced expertise in fetal echocardiography.2 It may also prove difficult to achieve low incidence angles for all cardiac, great vessel, and fetoplacental flow regions during an individual study. Therefore, estimation of transvalvar pressure gradients, assessment of volume flow, and quantitation of valvar regurgitation may be impossible. Despite these limitations, pathological flow profiles such as retrograde flow with atrial contraction inside the ductus venosus, pulsatile flow inside the umbilical vein, absent or reversed end-diastolic flow inside the umbilical artery, or turbulent flow across a stenotic valve can be depicted.2
The development of percutaneous fetoscopic techniques for fetal cardiac interventions has been supported by educational and research grants (Ko 1484/1-1, Ko 1484/2-1, Ko 1484/3-1, Ko 1484/3-2, Ko 1484/3-3) from the Deutsche Forschungsgemeinschaft (DFG), Bonn, Germany.
Dr Kohl has received educational and research grants from the German Research Society for the development of fetoscopic techniques for fetal cardiac intervention. Dr Kohl has also received industrial support from and has been a consultant for Karl Storz GmbH, Tuttlingen, Germany, an endoscopic instrument company. The other authors report no potential conflicts of interest.
Kohl T, Hering R, Van de Vondel P, Tchatcheva K, Berg C, Bartmann P, Heep A, Franz A, Müller A, Gembruch U. Analysis of the step-wise clinical introduction of experimental percutaneous fetoscopic surgical techniques for upcoming minimally-invasive fetal cardiac interventions. Surgical Endosc. 2006; 20: 1134–1143.
Kohl T, Hartlage MG, Westphal M, Kienitz D, Aryee S, Achenbach S, Buller T, Kossobutzki C, Gogarten W, Vogt J, Scheld HH, Van Aken H, Gembruch U. Intraamniotic multimodal fetal echocardiography in sheep: a novel imaging approach during fetoscopic interventions and for assessment of high-risk pregnancies in whom conventional imaging methods fail. Ultrasound Med Biol. 2002; 28: 731–736.