LONG-TERM FETAL-OUTCOME AFTER FETAL CARDIAC BYPASS - FETAL SURVIVAL TO FULL-TERM AND ORGAN ABNORMALITIES

Background: Earlier work suggests that fetal cardiac bypass is technic ally feasible but results in significant placental dysfunction. Many o f the stimuli that initiate this placental dysfunction have been ident ified in the past several years and these involve fetal stress, extrac orporeal surfaces, priming substances (maternal blood), and flow chara cteristics. Fetal survival with conventional methods of bypass has bee n far less than optimal, A novel fetal bypass circuit requiring no pri ming volume was designed incorporating an in-line axial flow pump (Hem opump, Johnson & Johnson Interventional Systems, Rancho Cordova, Calif ,) and was demonstrated to have a marked beneficial effect on placenta l function, Objective: The purpose of this study was to investigate th e effect of this newly developed customized fetal bypass circuit on fe tal survival and developing fetal organs, Methods and results: Nine fe tuses at 122 to 126 days of gestation were subjected to fetal cardiac bypass via a transsternal approach, with a 16F single right atrial ven ous cannula and a 12F arterial cannula, Normothermic cardiac bypass wa s continued for 30 minutes at how rates of 320 +/- 32 ml/kg, Of the ni ne fetuses? one Fetus was stillborn 4 days after bypass and eight (89% ) were delivered alive after progressing to term gestation, One lamb d ied of blunt trauma 1 day after birth, All other lambs (n = 7) thrived normally, and at 1 week of age they: were subjected to autopsy, No gr oss hemorrhagic or thromboembolic lesions were detected in the organs examined including the brain, Microscopic examination of representativ e sections from all organs revealed mild pleural reaction in two lambs , and in two other lambs the hepatocytes showed evidence of mild incre ase in glycogen content, the significance of which is unknown in relat ion to fetal bypass, In one fetus that was aborted there was evidence of mild to moderate neuronal loss in the cerebral cortex, Conclusion: This study demonstrates that with improvements in fetal extracorporeal circuitry and techniques very favorable fetal outcome can be achieved , Further studies are necessary to evaluate the effects of bypass on f etal brain in an appropriate animal model, Advances in extracorporeal circuitry to suit the unique fetal physiology increase the possibility of future clinical application.