Novel Technique for the Measurement of Fetal Right Modified Myocardial Performance Index Using Synchronized Images of Right Ventricular Inflow and Outflow and Clinical Application to Twin‐to‐Twin Transfusion Syndrome

Abstract

ObjectiveTo evaluate the reproducibility of the fetal right modified myocardial performance index (Mod‐MPI) obtained by synchronizing the inflow and outflow images of the right ventricle (RV) and to evaluate its feasibility through clinical application to twin‐to‐twin transfusion syndrome (TTTS).MethodsWe prospectively evaluated 77 normal fetuses. Two experienced operators individually measured the right Mod‐MPI using two different methods: (1) separate recording of the RV inflow and outflow using pulsed‐wave Doppler (conventional method) and (2) synchronization of RV inflow and outflow images using the MPI + ™ function based on the closure click of the pulmonary valve (new method). To evaluate the clinical utility of the new method, we measured the right Mod‐MPI in 33 TTTS fetuses using the new method before and after the fetoscopic laser coagulation (FLC).ResultsThere was no statistical difference in Mod‐MPI values between the two methods (p = .242). For both operators, the intra‐ and interoperator reproducibility of Mod‐MPI was high with both methods (ICCs >0.950). Among the components of Mod‐MPI measured using the new method, ejection time showed the highest reproducibility, whereas isovolumetric relaxation time demonstrated the lowest reproducibility. In TTTS fetuses, the Mod‐MPI significantly decreased after FLC in recipients, and there was no difference in MPI values before and after FLC in donors.ConclusionRight Mod‐MPI measurement after the synchronization of RV inflow and outflow images is a reliable technique for evaluating fetal right cardiac function. This novel method can also independently evaluate the systolic and diastolic functions of the right heart.