Fetal 4D flow MRI of the great thoracic vessels at 3 Tesla using Doppler-ultrasound gating: a feasibility study.

OBJECTIVES: To evaluate the feasibility of Doppler-ultrasound (DUS)-gated 4D flow MRI of the fetal great thoracic vessels at 3T in a clinical setting. METHODS: Sixteen consecutive fetuses (range 30+4-38+5 weeks) with (n = 11) and without (n = 5) cardiovascular anomalies underwent 4D flow MRI of the great thoracic vessels at 3T. Direct fetal cardiac gating was obtained using a MR-compatible DUS device. 4D flow MRI-based visualisation and quantification of four target regions (ascending aorta (AAo), descending aorta (DAo), main pulmonary artery (MPA), and ductus arteriosus (DA)) were performed using dedicated software. RESULTS: Fetal 4D flow MRI of the great thoracic vessels was successful in 12/16 fetuses (75%) by adopting clinical 4D flow MR protocols in combination with direct fetal cardiac DUS-gating. Four datasets were excluded due to artefacts by fetal movement or maternal breathing. 4D flow MRI-derived time-velocity curves revealed typical arterial blood flow patterns in the aorta. 4D flow quantification was achieved for the pre-defined target regions. Average velocity and flow volume were 21.1 ± 5.2 cm/s and 6.0 ± 3.1 mL/s in the AAo, 24.3 ± 6.7 cm/s and 8.4 ± 3.7 mL/s in the DAo, 21.9 ± 6.4 cm/s and 7.8 ± 4.2 mL/s in the MPA, and 23.4 ± 4.7 cm/s and 5.9 ± 3.6 mL/s in the DA, respectively. CONCLUSIONS: Combination of DUS-gating of the fetal heart and 4D flow MRI allows comprehensive visualisation and quantification of haemodynamics in the fetal great thoracic vessels. DUS-gated fetal 4D flow MRI may provide a new diagnostic approach for prenatal assessment of blood flow haemodynamics. KEY POINTS: • Fetal cardiac Doppler-ultrasound (DUS) gating and 4D flow MRI can be successfully combined. • DUS-gated fetal 4D flow MRI allowed visualisation and evaluation of streamline directionality, illustration of blood flow variations, and pulsatile arterial waveforms in the target vessels. • 4D flow MRI-based visualisation and quantification of the fetal great thoracic vessels were successful and flow metrics agreed with echocardiographic reference values.

First-trimester intervention in twin reversed arterial perfusion sequence.

OBJECTIVE: To report the outcome of monochorionic twins with twin reversed arterial perfusion (TRAP) sequence following interstitial laser therapy in the first trimester. METHODS: This was a retrospective cohort study of all consecutive cases of TRAP that underwent interstitial laser therapy at ≤ 14 + 3 weeks' gestation between January 2014 and April 2016. Interstitial laser treatment was performed under ultrasound guidance using a 400-nm Nd:YAG laser fiber. Hospital records were reviewed to ascertain perinatal survival and morbidity. RESULTS: Twelve monochorionic twin pregnancies underwent interstitial laser treatment of the umbilical artery of the acardiac fetus, at a median gestational age of 13 + 5 (interquartile range (IQR), 13 + 4 to 14 + 0) weeks. In all cases, one treatment was sufficient to achieve complete interruption of the perfusion of the acardiac twin. There were no procedure-related complications during or within 48 h after the procedure. In one (8.3%) case, intrauterine death of the pump twin occurred 2 weeks after the intervention. All other cases (91.7%) resulted in a live birth at a median gestational age of 39 + 6 (IQR, 37 + 1 to 41 + 2) weeks and with a median birth weight of 3370 (IQR, 2980-3480) g. No neonatal mortality or serious morbidity occurred. CONCLUSIONS: Our results support the use of interstitial laser therapy in the first trimester of pregnancy complicated by TRAP sequence, showing a live birth rate of 92%. The results of a randomized controlled trial, evaluating early vs late intervention in pregnancy with TRAP sequence, are awaited. © 2019 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Fetal dynamic phase-contrast MR angiography using ultrasound gating and comparison with Doppler ultrasound measurements.

OBJECTIVES: To investigate the feasibility of fetal phase-contrast (PC)-MR angiography of the descending aorta (AoD) using an MR-compatible Doppler ultrasound sensor (DUS) for fetal cardiac gating and to compare velocimetry with Doppler ultrasound measurements. METHODS: In this prospective study, 2D PC-MR angiography was performed in 12 human fetuses (mean gestational age 32.8 weeks) using an MR-compatible DUS for gating of the fetal heart at 1.5 T. Peak flow velocities in the fetal AoD were compared with Doppler ultrasound measurements performed on the same day. Reproducibility of PC-MR measurements was tested by repeated PC-MR in five fetuses. RESULTS: Dynamic PC-MR angiography in the AoD was successfully performed in all fetuses using the DUS, with an average fetal heart rate of 140 bpm (range 129-163). Time-velocity curves revealed typical arterial blood flow patterns. PC-MR mean flow velocity and mean flux were 21.2 cm/s (range 8.6-36.8) and 8.4 ml/s (range 3.2-14.6), respectively. A positive association between PC-MR mean flux and stroke volume with gestational age was obtained (r = 0.66, p = 0.02 and r = 0.63, p = 0.03). PC-MR and Doppler ultrasound peak velocities revealed a highly significant correlation (r = 0.8, p < 0.002). Peak velocities were lower for PC-MR with 69.1 cm/s (range 39-125) compared with 96.7 cm/s (range 60-142) for Doppler ultrasound (p < 0.001). Reproducibility of PC-MR was high (p > 0.05). CONCLUSION: The MR-compatible DUS for fetal cardiac gating allows for PC-MR angiography in the fetal AoD. Comparison with Doppler ultrasound revealed a highly significant correlation of peak velocities with underestimation of PC-MR velocities. This new technique for direct fetal cardiac gating indicates the potential of PC-MR angiography for assessing fetal hemodynamics. KEY POINTS: • The developed MR-compatible Doppler ultrasound sensor allows direct fetal cardiac gating and can be used for prenatal dynamic cardiovascular MRI. • The MR-compatible Doppler ultrasound sensor was successfully applied to perform intrauterine phase-contrast MR angiography of the fetal aorta, which revealed a highly significant correlation with Doppler ultrasound measurements. • As fetal flow hemodynamics is an important parameter in the diagnosis and management of fetal pathologies, fetal phase-contrast MR angiography may offer an alternative imaging method in addition to Doppler ultrasound and develop as a second line tool in the evaluation of fetal flow hemodynamics.

Role of fetal intertwin difference in middle cerebral artery peak systolic velocity in predicting neonatal twin anemia-polycythemia sequence.

OBJECTIVES: To evaluate the relationship between the fetal intertwin difference in middle cerebral artery peak systolic velocity (MCA-PSV) and intertwin difference in hemoglobin (Hb) concentration at birth in monochorionic diamniotic (MCDA) twin pregnancies in order to assess its potential role in the prediction of twin anemia-polycythemia sequence (TAPS). METHODS: This was a retrospective cohort study of MCDA twin pregnancies delivered between January 2012 and January 2018. All pregnancies with measurements of MCA-PSV within 7 days prior to delivery and in which neonatal Hb concentration was available were included. The correlation between fetal intertwin difference in MCA-PSV, expressed in multiples of the median (MoM), and neonatal intertwin difference in Hb concentration was investigated. Receiver-operating characteristics (ROC) curve analysis was used to assess the performance of fetal intertwin difference in MCA-PSV for predicting intertwin difference in Hb > 90th centile at birth. RESULTS: A total of 154 out of 256 MC twin pregnancies fulfilled the inclusion criteria. Fetal intertwin difference in MCA-PSV MoM correlated positively with neonatal intertwin difference in Hb concentration (r = 0.79; P < 0.001). The 90th centile for intertwin difference in Hb was 7.25 g/dL. There were 15 (9.7%) cases with a Hb difference ≥ 7.25 g/dL at birth. ROC curve analysis showed a high accuracy of fetal intertwin MCA-PSV MoM difference for the prediction of neonatal intertwin Hb difference ≥ 7.25 g/dL at birth (area under the ROC curve, 0.976 (95% CI, 0.935-0.993); P = 0.012). The optimal cut-off for intertwin MCA-PSV MoM difference was 0.373, with a sensitivity of 93.3% (95% CI, 68.1-99.8%) and a specificity of 95.7% (95% CI, 90.8-98.4%). The positive predictive value was 70% (95% CI, 45.7-88.1%) and the negative predictive value was 99.3% (95% CI, 95.9-100%). CONCLUSION: Our findings show that fetal intertwin MCA-PSV MoM difference is a good predictor of neonatal intertwin Hb concentration difference > 90th centile and potentially of TAPS. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Dynamic fetal cardiac magnetic resonance imaging in four-chamber view using Doppler ultrasound gating in normal fetal heart and in congenital heart disease: comparison with fetal echocardiography.

OBJECTIVES: To investigate the diagnostic performance of dynamic fetal cardiac magnetic resonance imaging (MRI), using a MR-compatible Doppler ultrasound (DUS) device for fetal cardiac gating, in differentiating fetuses with congenital heart disease from those with a normal heart, and to compare the technique with fetal echocardiography. METHODS: This was a prospective study of eight fetuses with a normal heart and four with congenital heart disease (CHD), at a median of 34 (range, 28-36) weeks' gestation. Dynamic fetal cardiac MRI was performed using a DUS device for direct cardiac gating. The four-chamber view was evaluated according to qualitative findings. Measurements of the length of the left and right ventricles, diameter of the tricuspid and mitral valves, myocardial wall thickness, transverse cardiac diameter and left ventricular planimetry were performed. Fetal echocardiography and postnatal diagnoses were considered the reference standards. RESULTS: Direct cardiac gating allowed continuous triggering of the fetal heart, showing high temporal and spatial resolution. Both fetal cardiac MRI and echocardiography in the four-chamber view detected pathological findings in three of the 12 fetuses. Qualitative evaluation revealed overall consistency between echocardiography and MRI. On both echocardiography and MRI, quantitative measurements revealed significant differences between fetuses with a normal heart and those with CHD with respect to the length of the right (P < 0.01 for both) and left (P < 0.01 for both) ventricles and transverse cardiac diameter (P < 0.05 and P < 0.01, respectively). Tricuspid valve diameter on cardiac MRI was found to be significantly different in healthy fetuses from in those with CHD (P < 0.05). CONCLUSIONS: For the first time, this study has shown that dynamic fetal cardiac MRI in the four-chamber view, using external cardiac gating, allows evaluation of cardiac anatomy and diagnosis of congenital heart disease in agreement with fetal echocardiography. Dynamic fetal cardiac MRI may be useful as a second-line investigation if conditions for fetal echocardiography are unfavorable. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Twin anemia-polycythemia sequence in a case of monoamniotic twins.

Twin anemia-polycythemia sequence (TAPS) complicates up to 6% of monochorionic diamniotic twin pregnancies, typically in the late second or third trimester. The presence of only a few and very small arteriovenous vascular anastomoses characterizes the underlying angioarchitecture at the chorionic plate in cases of TAPS. In monoamniotic twins, large vascular anastomoses can usually be seen at the placental vascular equator, and therefore one would not expect the development of TAPS in monoamniotic twins. We report a case of TAPS in a monoamniotic pregnancy at 26 + 5 weeks' gestation which responded favorably to fetoscopic laser coagulation of the small placental anastomoses, resolving severe anemia in one twin and polycythemia in the other. The pregnancy continued until 32 + 5 weeks, when worsening cord entanglement with increased resistance and the development of postsystolic notches in the umbilical artery of one twin prompted delivery by Cesarean section. There was only a moderate difference in neonatal hemoglobin concentrations, with the former polycythemic twin needing a single partial volume exchange transfusion. The postnatal course of the neonates was uneventful, according to their gestational age at birth. To our knowledge this is the first case report describing successful laser therapy for TAPS in monoamniotic twins.