STIC imaging of arterial valve morphology in congenital heart disease
Mani Ram Krishna and Usha Nandhini Senniyan
Tiny Hearts Fetal and Pediatric Cardiac Clinic
R.K. Hospital for Women and Children
Thanjavur, India
Correspondence to
Dr Mani Ram Krishna
Dr R.K. Hospital for Women and Children
No 7, V.O.C. Nagar
Thanjavur-613007
Tamil Nadu, India
E-mail: mann_comp@hotmail.com
Data availability statement: Additional data regarding the case is available with the authors and will be provided on request
Abstract
Spatio-temporal imaging correlation (STIC) technology has been employed to visualize the fetal heart for close to two decades, but the additional value of the technology remains debatable. The value of the technology in identifying the morphology of the cardiac valves is being recognized. We report a 21-week gestational age fetus with common arterial trunk where STIC imaging enabled us to identify a bicuspid arterial valve.
Introduction
The introduction of spatio-temporal image correlation technique (STIC) was considered a breakthrough in imaging of the fetal heart(1). Advancements in technology has resulted in a steady improvement in the image quality. However, despite two decades of its existence, the clinical utility of the technique remains a topic of debate. Experts in congenital heart diseases recognize that the technique offers very little additional diagnostic date over two-dimensional ultrasound and Doppler techniques in the hands of a skilled operator(2).
The authors believe that the greatest utility of STIC imaging is the ability to better visualize the morphology of the cardiac valves. This provides important diagnostic and prognostic information in congenital heart diseases (CHD) where valve morphology is a key determinant of outcomes after intervention(3).
We report a fetus with common arterial trunk identified at 21 weeks gestational age. A bicuspid arterial valve was suspected on two-dimensional ultrasound and confirmed by reconstruction of the STIC dataset.
Clinical Details
A primi-gravida mother was referred to us at 21 weeks of gestation for evaluation of a suspected CHD. The growth of the fetus was appropriate for gestational age and there were no major extra-cardiac anomalies.
There was usual arrangement of the abdominal organs and the atria. The heart was in the left hemithorax with the apex pointing to the left. The systemic and pulmonary venous drainage were normal. There was an adequate atrial communication in the oval fossa shunting right to left. The atrio-ventricular connections were concordant. The ventricles were balanced with normal ventricular function. There was a large mal-aligned peri-membranous ventricular septal defect (VSD). A common arterial trunk arose from the ventricular mass over-riding the VSD (Fig 1A and Video 1). This was an aortic dominance type of common trunk with the pulmonary arteries arising from the postero-lateral surface of the common trunk (Fig 1B and Video 1). The aortic arch was left sided, and an arterial duct was not visualized.
There was mild stenosis and mild incompetence of the valve of the common trunk (Fig 2A and 2B). The 2D appearance raised the suspicion of a bicuspid valve. Hence three-dimensional datasets were obtained by STIC both with and without color Doppler (Video 2). Reconstruction of the three-dimensional datasets confirmed a functionally bicuspid valve with fusion of two of the three leaflets (Fig 3A and B, Video 3).
Discussion
STIC imaging permits surface rendering and multi planar visualization of cardiac anatomy in the fetus. The value of STIC imaging in permitting offline expert analysis of cardiac abnormalities as well as a powerful teaching tool by creating libraries of fetal congenital heart diseases has been recognized for some time(2). Increasingly, the value of STIC imaging for visualization of the morphology of the atrio-ventricular and semilunar valves(4-6). Authors have focused on measurement of the valve area as well as counting the number of leaflets. However, such efforts appear to be limited to a handful of high-volume centers with long standing expertise in STIC imaging technology.
Nomograms have been published for the measurement of semilunar valve dimensions from multi-planar datasets obtained by STIC imaging(7). Adriaanse and colleagues attempted to measure the semilunar valve area and count the number of valve leaflets from more than 200 fetal datasets at various gestational ages(6). They reported a greater than 90% feasibility of measuring the area. When attempting to count the number of leaflets, they noticed that success was linked to the gestational age of the fetus with a higher probability at 19-24 weeks of gestation. The difficulty at advanced gestational ages was likely related to increased rib shadowing. When they extended their attempts to fetuses with CHD, they reported a similar high success rate in measuring valve area but did not attempt to count the number of leaflets. Our case highlights the feasibility of counting the number of leaflets and the valve morphology in fetuses with CHS
As short- and medium-term outcomes after congenital cardiac surgery has improved over the recent decades, the focus has shifted to very long-term outcomes extending into adulthood. It is being recognized that most re-interventions in adult survivors of congenital heart disease involve operations of the cardiac valves(8). This is best exemplified by common arterial trunk in which long term outcomes appear to be directly related to the degree of arterial valve dysfunction(9). The imaging of the valve morphology hence represents a very important prognostic information for counseling the expectant members and is likely best achieved in the 19–24-week gestational age period.
Our case illustrates the ability to demonstrate the semilunar valve morphology in fetuses with congenital heart disease. The quality of the dataset remains a major impediment to widespread use of this technique. Even in the best centers, only around 80% of datasets were found to be of adequate quality for analysis(6). It is likely that the numbers will be much lower in most centers performing fetal echocardiography. Improvement in technology to reduce noise during data acquisition could result in better datasets from less experienced operators and result in wider acceptance of this technology.
Compliance with ethical standards
Funding: This work did not involve any external funding
Conflict of Interest: The authors report no conflict of interest with regards to this work
Ethical approval: This article does not contain any studies with human participants or animals performed by any of the authors. Informed consent was obtained
References
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Figure Legends
Figure 1A – Two-dimensional ultrasound image of the fetus from a modified outflow tract view. The ventricles are balanced and there is a large mal-aligned ventricular septal defect. A single outflow tract (star) is seen over-riding the septal defect (LA – left atrium, LV – left ventricle, RV- right ventricle)
Figure 1B – Two-dimensional ultrasound image of the fetus. The branch pulmonary arteries (arrows) are seen bifurcating from a common trunk
Figure 2A – multi-planar rendered image of the heart obtained by spatio-temporal image correlation (STIC) technology with color Doppler demonstrating aliasing of flow across the arterial valve (star) which suggests stenosis of the valve
Figure 2B - multi-planar rendered image of the heart obtained by spatio-temporal image correlation (STIC) technology with color Doppler demonstrating regurgitation of flow across the arterial valve (arrow)
Figure 3A – A reconstructed image from a three-dimensional dataset of the fetal heart in diastole demonstrating the arterial valve leaflets (stars)
Figure 3B – A reconstructed image from a three-dimesnional dataset of the fetal heart in systole demonstrating a functionally bicuspid valve due to fusion of the two anterior leaflets(arrow)
Video 1 – A cine echocardiogram loop demonstrating the arterial trunk arising from the ventricular mass with the branch pulmonary arteries arising from the lateral surface of the common trunk
Video 2 – A reconstructed three-dimensional dataset using STIC technology with color Doppler demonstrating stenosis and regurgitation of the arterial valve
Video 3- A reconstructed three-dimensional dataset using STIC technology demonstrating the functionally bicuspid arterial valve with fusion of the two anteriorly located leaflets