Methods: Women carrying a fetus with suspected CoA on echocardiography were referred for MRI assessment between 26-36 weeks gestation, including high-resolution motion-corrected 3D volumes of the fetal heart and phase-contrast flow sequences gated with metric optimized gating. The relationship between aortic geometry and vascular flows was then analyzed and compared to postnatal outcome.
Results: 72 patients (51 with suspected fetal CoA and 21 healthy controls) underwent fetal MRI with motion-corrected 3D vascular reconstructions. Vascular flow measurements from phase contrast sequences were available in 53 patients. In the CoA group, 25/51 (49%) required surgical repair of coarctation after birth; the remaining 26/51 (51%) were discharged without neonatal intervention. Reduced blood flow in the fetal ascending aorta and at the aortic isthmus were associated with increasing angulation (p = 0.005) and proximal displacement (p = 0.006) and was seen in both true positive and false positive cases. A multivariate logistic regression model including aortic flow and isthmal displacement explained 78% of the variation in outcome and correctly predicted the need for intervention 93% of cases.
Conclusions: Reduced blood flow though the left heart is associated with important configurational changes at the aortic isthmus in fetal life, predisposing to CoA when the arterial duct closes after birth. Novel fetal MRI techniques may have a role in both understanding and accurately predicting severe neonatal CoA.
|Accepted/In press - 14 Apr 2021