REAL TIME ECHOCARDIOGRAPHIC DEMONSTRATION OF INTRACARDIAC AND EXTRACARDIAC RIGHT TO LEFT SHUNT RESPIRATORY DISTRESS SYNDROME

Abstract

It is not clear whether intracardiac or extracardiac (PDA) Rt to Lt shunt exists in respiratory distress syndrome. The purpose of this study is to use contrast echocardiography to demonstrate Rt to Lt shunt, if any, through foramen ovale (FO) and patent ductus arteriosus (PDA) in infants with RDS. ATL Mark III Real Time Ultrasound with 5 mHz scan head was used. The scan head was placed under xyphoid process to obtain a 4 chamber view. Two ml of normal saline was shaken before injecting into umbilical venous catheter placed at inferior vena cava (10 cases) or scalp vein when UV line was not available. The study was positive when both Rt and Lt atrium were opacified simultaneously. To study Rt to Lt PDA shunt, scan head was placed at lateral abdomen to visualize descending aorta. The study was positive when echodensity was visualized moving along aorta caudally. Twelve infants (m GA 30.3 wks, m BW 1607 gms) were studied. All were mechanically ventilated with FiO2 higher than 40%. Each patient was studied daily until shunt no longer existed. F.O. shunt was evident in all 12 patients who needed more than 40% of O2. Only 2 out of 12 patients had positive FO shunt at FiO2 of 30%, below which no shunt was visualized. PDA Rt to Lt shunt was visualized in 3 of 5 patients who required FiO2 >60%. No PDA shunts were seen below FiO2 of 60%. This study indicates that Rt to Lt shunting via FO and PDA exists in RDS.