Acquired right ventricular outflow tract obstruction in the recipient twinin twin-twin transfusion syndrome

OBJECTIVES The goal of this study was to determine the prevalence and evolu tion of acquired right ventricular outflow tract obstruction (RVOTO) in the recipient twin in twin-twin transfusion syndrome (TTTS). BACKGROUND Twin-twin transfusion syndrome complicates 4% to 26% of diamniot ic monochorionic twin gestations and is associated with high fetal morbidit y and mortality. Cardiac dysfunction and biventricular hypertrophy may deve lop in the recipient twin with the potential for RVOTO. METHODS This was a retrospective review of a two-center experience of TTTS to describe the prevalence and evolution of acquired RVOTO in the recipient twin. Right ventricular outflow tract obstruction was diagnosed or exclude d by, fetal or postnatal echocardiography or clinical assessment. RESULTS Of 73 twin pregnancies with TTTS identified between 1994 to 1998, a total of seven (9.6%) were complicated by RVOTO in the recipient twin: two subvalvar/muscular, four valvar and one combined. Of 44 pregnancies with f etal echo, six had in utero RVOTO with antegrade flow diagnosed at gestatio nal ages ranging from 19 to 27 weeks. In utero progression occurred in four cases over a period of four to eight weeks, with the development of RVOT a tresia by delivery. Postnatal progression of RVOTO occurred in two cases, o ne of which required pulmonary balloon valvuloplasty at age two years. Post natal regression of subvalvar RVOTO occurred in two cases in early infancy. Death related directly or indirectly to the RVOTO occurred in all four pat ients who developed complete RVOT obliteration. CONCLUSIONS Right ventricular outflow tract obstruction may occur in the re cipient twin of at least 9% of pregnancies complicated by TTTS. Right ventr icular outflow tract obstruction progression is common in utero and may, wo rsen neonatal outcome. (J Am Coll Cardiol 2001;38:1533-8) (C) 2001 by, the American College of Cardiology.