Abstract 9167: Fetoscopic Placental Laser Photocoagulation Improves Right Ventricular Outflow Tract Obstruction in Twin-Twin Transfusion Syndrome

Abstract

Background: Twin-twin transfusion syndrome (TTTS) is a disease of monochorionic, diamniotic twin gestation associated with recipient twin cardiac manifestations, such as abnormal growth of the pulmonary artery (PA) and right ventricular outflow tract obstruction (RVOTO). Untreated, mortality is >80%, however fetoscopic placental laser photocoagulation (LP) improves survival. Objectives: To characterize the impact of LP on PA abnormalities and RVOTO in recipient TTTS twins. Methods: TTTS gestations with abnormal recipient PA growth and RVOTO that underwent LP between 1/1/2009 to 12/31/2010 were identified. We previously developed a comprehensive cardiovascular scoring system for TTTS (CHOP Score), which includes a domain grade for right-sided outflow abnormality (0 = no obstruction, 1 = PA equal in size to aorta, 2 = PA smaller than aorta, and 3 = frank RVOTO with pulmonary stenosis or atresia). Fetal echocardiograms were reviewed to determine the CHOP Score before, 1 day, 1 week, and 4 weeks after LP. Results: Of 76 twin pairs with TTTS who underwent LP at our center, 28 (36%) had right-sided outflow abnormality. Prior to LP, 15 had a PA equal in size to the aorta (group 1), 5 had a PA smaller than the aorta (group 2) and 8 had frank RVOTO (group 3). Median gestational age at LP was 20 wks (17 6/7-25 5/7 wks). The impact of LP is shown. All group 1 and group 2 fetuses had complete resolution by 4 wks after LP. In group 3, 1 patient with “functional” pulmonary atresia (no antegrade flow but with pulmonary insufficiency) had complete resolution 1 day after LP. Five patients (63%) with RVOTO at diagnosis did not respond to LP, of whom four required a catheter-based intervention after birth. All four remained biventricular repairs. There were 11 cases of fetal demise (6 donor, 5 recipient). Conclusions: Placental LP interrupts the pathophysiology of TTTS and leads to improvement in RVOTO. The disease model of TTTS provides an opportunity to study the unique plasticity of the human fetal heart.