Abstract Body (Do not enter title and authors here): Background: Fetal anemia can lead to high cardiac output (CO) failure, fetal hydrops and fetal demise. Intrauterine transfusion (IUT) is the standard of care, but carries risks of premature delivery and fetal death; therefore, it is critical to identify the most affected fetuses prior to intervention. Elevation of the peak systolic velocity in the middle cerebral artery (MCA-PSV) is routinely used to indicate intervention; however, the reported false positive rate is as high as 12 to 14%.
Aim: Assess whether measured CO by fetal echocardiography (FE) can be used as a complementary screening tool to predict fetal anemia.
Methods: We identified all pregnancies referred for FE from 2009-2023 with suspected fetal anemia (n=49). We reviewed FEs (n=88) to measure ventricular function, combined CO (aortic and pulmonary outflows), and measured ventricular dimensions. Percentiles for CO were used based on published normative data. The MCA-PSV was measured and reported as multiples of the median (MoM). Where available, pre-transfusion fetal hemoglobin (Hb) readings were reported as a MoM, with temporally matched FE studies performed prior to IUT included for analysis (n=8).
Results: Overall, MCA-PSV was positively associated with left ventricular (LV) CO, but not with right ventricular (RV) or combined (CCO) (LV CO p=0.037, Figure 1A; RV CO p=0.790; CCO p=0.290). The LV CO correlated with z-scores for LV and RV end diastolic dimensions (EDD) (LVEDD p<0.001; RVEDD p=0.018). The RV CO and CCO also were positively associated with LVEDD (p=0.004 and p<0.001, respectively), and RVEDD (p=0.009 and p=0.003, respectively). However, the MCA-PSV did not correlate with ventricular dimensions (LVEDD p=0.524 and RVEDD p=0.689). Fetal Hb was negatively correlated with the MCA-PSV, which approached statistical significance (Figure 1B). Fetal Hb negatively correlated with the LV CO (Figure 1C), but not with RV CO or CCO (Figure 1D).
Conclusion: Preliminary results suggest that fetal LV CO may confer additive value to current MCA-PSV measurement in predicting the severity of fetal anemia. Larger studies are warranted to explore the relationship of fetal LV CO and MCA-PSV with fetal Hb and prognosis in high output cardiac failure.