1354417 - Feasibility assessment of fetal 4D Flow CMR

4D Flow cardiovascular magnetic resonance (CMR) is increasingly utilised clinically for comprehensive hemodynamic assessment, especially in congenital heart disease (CHD). Developments in acceleration of both acquisition and post-processing, as well as in Doppler ultrasound (DUS) based fetal cardiac gating (Smart-sync, Northh Medical, Hamburg, Germany) have recently improved the practical feasibility of performing this technique prenatally. However, there has yet been little adoption or reporting of this in fetal patients with CHD. Especially in later gestation echocardiographic views can be limited and fetal CMR can add valuable information to aid perinatal care.

This pilot study therefore aims to demonstrate the feasibility and assess the potential clinical utility of easily accessible fetal 4D Flow CMR. 

Methods:

11 pregnant women were prospectively recruited from fetal cardiology clinics and underwent fetal CMR at a median gestation 34+5weeks (range 31+6–37+1 weeks) on a 3T clinical scanner (MAGNETOM Prisma 3T, Siemens Healthineers, Erlangen, Germany). For safety, scanning was limited to 30min with the lowest available gradient mode used. DUS was used for cardiac gating. Bright blood stacks for planning, gradient echo cine imaging for valve tracking and compressed sensing (CS) 4D Flow CMR (acquired resolution 1.5mm) for flow assessment were acquired. The CS 4D Flow CMR sequence used is extensively validated in neonates(1). Analysis was completed with commercially available analysis software (PIE medical imaging software, CASS, The Netherlands).

Results:

The CMR scan was well tolerated by all 11 women. 4D Flow CMR assessment was successful in 8/11 fetuses(Figure 1+2). Two failed due to fetal movement (polyhydramnios in one) and one due to maternal movement (twin pregnancy). Median CS 4D Flow CMR acquisition time was 3min58 sec(range: 3min24sec–4min49sec). Analysis took < 15min in all cases.

2 fetuses had no cardiac abnormalities. In the remaining 6 fetuses CS 4D Flow CMR added extra information in 5/6 cases.

In 3 cases fetal CS 4D Flow CMR assessment added quantification of tricuspid regurgitation which was validated with postnatal CS 4D Flow CMR quantification in one case(Figure 3). Tricuspid regurgitation fraction was 10% on fetal and 15% on postnatal CS 4D Flow CMR.

In 2 TGA cases with aneurysmal septum, 4D Flow CMR assessment showed that the atrial septum was not restrictive which was confirmed on postnatal echocardiogram and clinical picture using previously published fetal 2D flow cut off values as guide(2). 

4D Flow CMR was unable to visualise the VSD seen on echocardiography prenatally in one case and did not add any extra information. 

 

Conclusion:

4D flow CMR using commercially available equipment and analysis platforms is feasible with a success rate of around 70%. It has the potential to provide valuable haemodynamic quantification in a number of congenital heart diseases. However, case selection is important as it does not add relevant information in all cases.