The persistent changes in cardiac structure and function in children who survived twin-to-twin transfusion syndrome remain a matter of concern and controversy. Current fetal echocardiographic parameters and their postnatal evolution can help improve our understanding of the subject.

To describe the echocardiographic changes of monochorionic fetuses affected by twin-to-twin transfusion syndrome, the recipient and the donor, before and after laser photocoagulation and to determine their evolution in the third trimester and during their first year of life.

An observational study was conducted including 55 uncomplicated monochorionic diamniotic twins and 78 pairs with twin-to-twin transfusion syndrome, 44 stage I-II and 34 stage III-IV, prospectively enrolled from 2015 until 2018. Comprehensive echocardiography was performed at 4 time periods: before laser photocoagulation, at 24 to 72 hours after surgery, at 28 to 30 weeks of gestation, and at 6 to 12 months after birth. Echocardiographic parameters were transformed to z-scores or indexed for heart area, estimated fetal weight, or body mass surface.

At diagnosis, recipients in all stages presented larger hearts (cardiothoracic ratio z-score: 2.77 [0.8] vs controls: −0.03 [0.5]; P<.001) and signs of ventricular hypertrophy (left end-diastolic ventricle wall thickness: 2.68 [0.7] vs controls −0.03 [0.7]; P<.001), along with systolic (cardiac index recipients: 317 [114] mL/min/kg vs controls: 400 [120] mL/min/kg, P<.001) and diastolic impairment (isovolumetric relaxation time z-score: 2.76 [0.6] vs controls: 0.05 [0.6]; P<.001). Donors presented smaller ventricular areas and diameters when compared with controls (left end-diastolic ventricle area z-score: −1.48 [1] vs 0.03 [0.9]; P<.001), along with decreased longitudinal motion (tricuspid annular plane systolic excursion z-score: −0.9 [1] vs controls −0.04 [1]; P<.001) and shorter ejection time z-score (−1.5 [0.7] vs controls: 0.0 [0.7]; P<.001). After surgery, an improvement in functional parameters was observed in both fetuses, whereas most morphometric changes prevailed in donors and recipients in the prenatal period. Postnatally, cardiac remodeling persisted in recipients (left relative wall thickness: 0.34 [0.02] vs controls: 0.30 [0.02]; P<.001), whereas donors mainly presented a decreased longitudinal motion in infancy (tricuspid annular plane systolic excursion z-score: −0.72 [0.7] vs controls: 0.23 [0.9]; P<.05).

Cardiac remodeling is present in both fetuses at the twin-to-twin transfusion syndrome diagnosis, whereas diastolic dysfunction is only significant in the recipient. Fetal therapy improves most echocardiographic parameters, although postnatally, the echocardiographic changes persist in both fetuses.