Is There a Measurable Difference between the Left and Right Modified Myocardial Performance Indices, and Does This Change to Reflect Unilateral Myocardial Dysfunction in Pathology?

ABSTRACT

INTRODUCTION: Fetal cardiac dysfunction may manifest itself unilaterally as right and left ventricles differing in design, function and load, measurable as differing in myocardial performance indices (MPIs). We wished to define this difference ('delta-MPI' or DMPI), present its normal range and pilot its use in pathological pregnancy. MATERIAL AND METHODS: Prospective cross-sectional study of 324 normal singleton fetuses (16-38 weeks of gestation). Left and right modified MPI (LMPI and RMPI) were performed during a single examination using the 'peak' valve click technique. Thirty-seven pathological singleton and monochorionic diamniotic twin pregnancies were compared as pilot data. RESULTS: Modified MPIs (mean ± SD) were 0.45 ± 0.06 (LMPI) and 0.47 ± 0.09 (RMPI), being similar at 18 weeks' gestation with DMPI increasing slightly throughout pregnancy (0.02 ± 0.08). Both singleton intrauterine growth restriction (IUGR) and recipient twin-twin transfusion syndrome (TTTS) showed significantly elevated RMPI, LMPI and DMPI, most pronounced for DMPI (450 and 500% increase, respectively; p < 0.01). DMPI acquisition rates were 83.3% normal and 87.0% pathological. DISCUSSION: We demonstrate for the first time differing intrafetal LMPI and RMPI in a large gestational cohort, with this difference increasing with gestational age. Pilot data confirm the potential for DMPI as a tool to assess unilateral myocardial function in singleton IUGR and recipient twins in TTTS, and further studies are under way to evaluate its clinical utility.