Challenges for prenatal diagnosis of congenital heart disease 

 

The clinical gold standard for prenatal diagnosis of congenital heart disease is fetal echocardiography which is the number one choice for diagnosis and treatment decisions. For significant congenital heart defects (CHD), occurring with an incidence of 6 to 1 in 1000 live births worldwide (1), cardiac imaging is particularly important. 

The challenge

The challenges in fetal echocardiography is to obtain good acoustic windows especially in cases of maternal obesity and oligohydramnios. Moreover, the visualisation of the fetal heart is challenging in the third trimester due to fetal position and increased shadowing from calcified ribs which limits the acoustic window of ultrasound (2). Hence, a diagnosis of CHD is especially challenging when the patients have the first suspicion of CHD in late gestational week.  Depending on training, equipment, examination practice and the screened population the sensitivity varies widely. As an example the prenatal detection rate of CHD which require surgery is only 42% (3)  in the United States.   

 

What imaging modality can be used as alternative? 

In patients in which there is uncertainty about the cardiac morphology after echocardiography, the combination of fetal cardiac Magnetic Resonance has been shown to provide additional diagnostic information over ultrasound alone (4). 

 

Use of magnetic resonance imaging 

As an alternative to fetal echocardiography the MRI is the method of choice. The MRI provides imaging without radiation with a relatively high spatial resolution and independence from acoustic windows limiting the ability to image important structures. The use of MRI for cardiac imaging is highly adopted for adults and neonates in clinical routine. However, the translation of conventional cardiac MR imaging for prenatal examinations is difficult as the cardiac rhythm needs to be synchronized with the cardiac cycle. Normally ECG surface electrodes are used that can not be used for this case. 

 

Why is smart-sync important? 

In order to be able to translate conventional cardiac MR imaging for the prenatal examination of the fetus, we have developed smart-sync in cooperation with the University Medical Center Hamburg-Eppendorf. Cardiac MR sequences can be normally gated using the heartbeat, enabling the use of a standard cardiac MR sequences to achieve an comprehensive analysis of cardiac anatomy (5,6) and functional assessment of the heart including important measurements of the blood flow in the great vessels (7).

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"The application of smart-sync for fetal cardiac MRI allows the translation of standard cardiac examination to the prenatal examination"

Prof. Dr. Jin Yamamura, University Medical Center Hamburg-Eppendorf.

 

How does fetal cardiac MRI with smart-sync work? 

The ultrasound transducer is placed on the belly above the fetal heart and is fixed with an elastic belt. The heartbeat is then detected with Doppler ultrasound and is shown on the screen of the display. The gating signal is sent wirelessly to the MR system for cardiac gating.

Locate the fetal heart and fix the transducer with the belt

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The fetal heartbeat is detected and send wirelessly to the MR System

"The fetal cardiac gating enables us to achieve MR images of the fetal heart with improved diagnostic quality."

Dr. Vanessa Berger-Kulemann, Radiology specialist

The prototype of the product version smart-sync has been used in multiple studies to evaluate safety and performance 

The early prototype and predecessor of smart-sync was developed at the department of diagnostic and interventional radiology and nuclear medicine at the University Medical Center in Hamburg-Eppendorf, Germany. Since 2018 the laboratory prototype was used in several feasibility studies and early clinical studies.

 

Evaluation of cardiac anatomy

The studies showed that high-quality dynamic fetal cardiac images can be acquired (5) in four chamber and short axis view that allow the evaluation of cardiac anatomy and diagnosis of CHD in agreement with fetal echocardiography (8). Moreover, one feasibility study showed that dynamic MR imaging of the fetal aorta has the potential to serve as a complementary imaging tool in cases where echocardiography is inconclusive (2).

Dr. Björn Schönnagel (Radiologist), Dr Manuela Tavares de Sousa (Gynecologist)  and Prof. Dr. Jin Yamamura (Radiologist) from the University Medical Center Hamburg-Eppendorf

Evaluation of blood flow

The measurement of 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.  

The gating with ultrasound allowed the measurement of intrauterine phase-contrast MR angiography of the aorta with a significant correlation to Doppler ultrasound (7). The gating with Doppler ultrasound was successfully applied to perform intrauterine phase-contrast MR angiography of the fetal aorta, which revealed a highly significant correlation with Doppler ultrasound as well the quantification of blood flow in the umbilical vein (9).

More recently a preliminary study showed the applicability of 4D phase-contrast angiography to visualize the blood flow and hemodynamics of the great vessels. The application may be beneficial for quantification of complex congenital cardiovascular malformations (10).

"smart-sync provides the cardiac gating signal that is necessary to run standard cardiovascular MR sequences with diagnostic quality."

Dr. Björn Schönnagel, Radiology specialist

2D SSFP CINE 

Four Chamber View: Typically used to assess cardiac function and morphology

4D PC Angiography:

Typically used to visualize the blood flow and hemodynamics 

2D SSFP CINE:

Short Axis Stack: Typically used to assess cardiac function and morphology

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References:

  1. Hoffman, J. I. & Kaplan, S. The incidence of congenital heart disease. J Am Coll Cardiol 39, 1890–1900 (2002).

  2. Tavares de Sousa M, Hecher K, Kording F, Yamamura J, Lenz A, Adam G, et al. Fetal dynamic magnetic resonance imaging using Doppler ultrasound gating for the assessment of the aortic isthmus: A feasibility study. Acta Obstet Gynecol Scand 2020:1–7.

  3. Hendler, I. et al. The impact of maternal obesity on midtrimester sonographic visualization of fetal cardiac and craniospinal structures. International journal of obesity and related metabolic disorders: journal of the International Association for the Study of Obesity 28, 1607–1611, https://doi.org/10.1038/sj.ijo.0802759 (2004)

  4. Marini D, Xu J, Sun L, Jaeggi E, Seed M. Current and future role of fetal cardiovascular MRI in the setting of fetal cardiac interventions. Prenat Diagn 2020;40:71–83.

  5. Kording F, Yamamura J, Tavares De Sousa M, Ruprecht C, Hedström E, Aletras AH, et al. Dynamic fetal cardiovascular magnetic resonance imaging using Doppler ultrasound gating. J Cardiovasc Magn Reson 2018;20:1–10.

  6. Roy CW, Seed M, van Amerom JFP, Al Nafisi B, Grosse-Wortmann L, Yoo S-J, et al. Dynamic imaging of the fetal heart using metric optimized gating. Magn Reson Med 2013;70:1598–607.

  7. Schoennagel BP, Yamamura J, Kording F, Fischer R, Bannas P, Adam G, et al. Fetal dynamic phase-contrast MR angiography using ultrasound gating and comparison with Doppler ultrasound measurements 2019.

  8. Tavares de Sousa M, Hecher K, Yamamura J, Kording F, Ruprecht C, Fehrs K, et al. 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. Ultrasound Obstet Gynecol 2019;53:669–75.

  9. Salehi D, Sun L, Steding-Ehrenborg K, Bidhult S, Kording F, Ruprecht C, et al. Quantification of blood flow in the fetus with cardiovascular magnetic resonance imaging using Doppler ultrasound gating: Validation against metric optimized gating. J Cardiovasc Magn Reson 2019;21:1–15.

  10. de Sousa MT, Schoennagel B, Kording F, Yamamura J, Adam G, Hecher K. VP15.13: Fetal cardiac 4D phase contrast MRI using Doppler ultrasound gating to visualise fetal hemodynamics in utero: preliminary results. Ultrasound Obstet Gynecol 2020;56:115–6.