Effect of Fetal Cardiac Bypass on Fetal Cardiovascular System: Fetal Lamb Study

Choi, Jung Yun; Huh, June; Kim, Yong Jin; Kim, Won Gon; Lee, Jeong Ryul; Kim, Chong Sung

Abstract

PURPOSE: This study was aimed to evaluate the feasibility of echo-Doppler study on fetal lamb, analyse the distribution of blood flow before and after fetal cardiac bypass, and consequently assess the effect of fetal cardiac bypass on the fetal cardiovascular system.
METHODS
Ten fetal lambs at 120 to 150 days of gestation which underwent cardiac bypass for 30 minutes were studied by echocardiography and Doppler study. Five fetuses survived after bypass. Blood flow volume was measured if possible in aorta, main pulmonary artery, ductus and branch pulmonary arteries before and after bypass.
RESULTS
Echocardiographic evaluation was successful in 5 of 9 studied in utero, and all 3 exteriorized cases before bypass and all 5 post-bypass cases. Before bypass cardiac output and combined vascular resistance tended to increase according to body weight, but was not significant. After cardiac bypass, cardiac output decreased significantly(P<0.05). The ratios of main pulmonary artery to aorta blood flow volume were 1.40(1.16-1.58) at pre-bypass and 1.47(0.644- 2.34) at post-bypass(P>0.05). Combined vascular resistance was 188unit(92-340unit) at pre-bypass and 341 unit(128-533 unit) at post-bypass. There was no significant difference in combined vascular resistance in 3 cases of which both pre-bypass and post-bypass studies were completed. Doppler study demonstrated systolic forward flow and diastolic reverse flow in ductus and aorta after cardiac bypass.
CONCLUSION
Echocardiography and Doppler study are feasible methods for the evaluation of blood flow after fetal cardiac bypass. This study suggests that cerebral and pulmonary vascular resistance may elevate less compared with that of placenta after cardiac bypass.