Extracorporeal circulation in ewe's foetus: towards a reliable foetal cardiac surgery protocol - A comparison of two cases

Foetal cardiac surgery is the ultimate goal in the treatment of congenital cardiac malformations. The aim of our research is to elucidate some of the features of the necessarily invasive experimental protocol to be used in an animal model of foetal cardiac surgery. In particular we assessed the foetal placentar reactivity to prolonged cardiac bypass in steady-flow conditions. Methods. Two cases were selected to show the outcome of prolonged (> 30 minutes) extracorporeal circulation (ECC) instituted without oxygenator under steady-flow assistance. Following the instrumentation of the animal (placement of pressure, flow and myocardial fiber length transducers) and the baseline recordings, a 60-minute bypass period was established with an axial turbopump (Hemopump 14 Fr), after systemic heparinisation and artero-venous cannulation. At the end of the circulatory assistance, the cannulae were removed and a 90 minute observation period followed. The cardiac function was assessed by means of indirectly obtained P-V loops. Results. Case A showed a marked reduction in the end-systolic pressure-volume relationship (ESPVR) during ECC, corresponding to a rightward shift of the P-V loop, with a gradual recovery after the assisted circulation. On the contrary case B was subjected to progressive placental dysfunction, as evidenced by haemogasanalytical data. Consequently, the haemodynamic data also outlined a negative outcome, with high ESPVR values after bypass. Conclusions. The present study, while confirming the possibility of cardiac intervention in the foetus, underlines the critical role of minimally invasive protocol to limit both foetal stress and placental dysfunction.