DOI: 10.1111/echo.13578
Isolated coarctation of the aorta in the fetus: A diagnostic challenge Joshua A. Kailin MD
| Alexia B. Santos MD | Betul Yilmaz Furtun MD |
S. Kristen Sexson Tejtel MD, PhD, MPH | Regina Lantin-Hermoso MD Baylor College of Medicine, Texas Children’s Hospital, Houston, TX, USA Correspondence Joshua A. Kailin, Baylor College of Medicine, Texas Children’s Hospital, Houston, TX, USA. Email:
[email protected]
Isolated coarctation of the aorta (CoA) is estimated by the Centers for Disease Control and Prevention to account for 4%–6% of all congenital heart disease (CHD) in the United States, with a reported prevalence of ~4 per 10 000 live births. Prenatal recognition of coarctation is important as it may improve neonatal survival and reduce morbidity. However, despite advances in imaging and the trend toward detailed aortic arch assessment as part of a comprehensive fetal echocardiogram, isolated CoA may still elude prenatal detection, with potentially lethal consequences if the diagnosis is not suspected and the patent ductus arteriosus (PDA) closes spontaneously in postnatal life. The purpose of this review is to outline the methods of antenatal aortic arch evaluation in the current era, discuss “red flags” that raise the suspicion for CoA, including associated anomalies and serve as a repository of the most up to date information regarding its diagnosis in utero and its perinatal management. Other aortic arch abnormalities, such as interrupted aortic arch, or CoA associated with complex single ventricles, are not included in this review. KEYWORDS
aorta coarctation, echocardiography, fetal echocardiography
1 | INTRODUCTION
management. Other aortic arch abnormalities, such as interrupted aortic arch, or CoA associated with complex single ventricles, are not
Isolated coarctation of the aorta (CoA) is estimated by the Centers for
included in this review.
Disease Control and Prevention to account for 4%–6% of all CHD in the United States, with a reported prevalence of ~4 per 10 000 live births.1 Prenatal recognition of coarctation is important as it may improve
2 | ASSESSMENT OF THE AORTIC ARCH IN UTERO
neonatal survival and reduce morbidity.2 However, despite advances in imaging and the trend toward detailed aortic arch assessment as
A clinical suspicion or a risk factor for CoA must be identified during
part of a comprehensive fetal echocardiogram,3 isolated CoA may still
routine obstetric screening to prompt referral for fetal echocardiog-
elude prenatal detection, with potentially lethal consequences if the
raphy. Guidelines for sonographic screening of the fetal heart from
diagnosis is not suspected and the patent ductus arteriosus (PDA)
the International Society for Ultrasound in Obstetrics and Gynecology
closes spontaneously in postnatal life.4 The purpose of this review
include obtaining the four-chamber and outflow tract views in all
is to outline the methods of antenatal aortic arch evaluation in the
pregnancies as part of routine mid gestation evaluation for CHD.5 The
current era, discuss “red flags” that raise the suspicion for CoA, in-
addition of the three vessel and trachea view, which is increasingly
cluding associated anomalies and serve as a repository of the most up
possible to obtain as early as 11–14 weeks gestational age due to im-
to date information regarding its diagnosis in utero and its perinatal
provements in imaging technology, has allowed recognition of subtle
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wileyonlinelibrary.com/journal/echo
Echocardiography. 2017;34:1768–1775.
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differences in great vessel caliber in the late first trimester. This has consequently increased the number of women selectively referred for targeted fetal echocardiography.6,7 These evolving obstetric practice guidelines are likely to increase the prenatal detection rate of CHD, including CoA.8 The optimal time to perform a fetal echocardiogram is between 18 and 22 weeks’ gestation.3 After 33–34 weeks, it is possible, albeit more challenging, to obtain adequate cardiac and aortic arch images as the fetal bones become more ossified and the fetus becomes crowded within the amniotic cavity due to the decrease in the amniotic fluid:fetal mass ratio. Ultrasound systems that include two-dimensional, Mmode, color, and pulsed-wave Doppler capabilities with settings that allow for appropriate frame rates and dynamic zoom are ideal.3 The highest frequency transducer, preferably 5 MHz or greater, depending on maternal habitus, is recommended to provide adequate penetration to view fetal cardiac structures in trans-abdominal evaluations.9 A curvilinear probe may be helpful to increase the field of view. The aortic arch should be evaluated in multiple views. Care should
F I G U R E 1 Four-chamber (4Ch) view demonstrates size discrepancy between the right ventricle (RV) and left ventricle (LV) with relative hypoplasia of the LV [Colour figure can be viewed at wileyonlinelibrary.com]
be taken to distinguish the fetal aortic arch, which gives rise to the brachiocephalic vessels, from the ductal arch, as these are easily confused and lie side by side. Imaging techniques to demonstrate long- and short-axis sweeps of the fetal heart and great vessels that constitute a complete fetal cardiac evaluation have been described.
3
Qualitative assessment and quantitative measurements of all fetal cardiac structures, which are compared to norms based on gestational
2.3 | Assessment of the great arteries The great vessels may be measured in both the long- and short-axis views, when the walls of the vessels are perpendicular to the ultrasound beam. The vessel internal diameter, leading edge to leading edge, is measured in diastole when its respective semilunar valve is closed.
age, are essential in the assessment for CoA in utero. Its antenatal recognition may be improved by serial studies that evaluate growth of cardiac structures as pregnancy progresses, in comparison with normative data. There are several z-score packages available for evalua10–13
2.4 | Assessment of the aortic dimensions Aortic dimensions are obtained at the level of the aortic valve annulus,
When evaluating structures
ascending aorta (AAo), transverse aortic arch, isthmus, and descend-
for serial growth, consistently utilizing the same z-score package that
ing aorta (Figure 2A). The measurements are taken from leading edge
adjusts for gestational age is just as important as which one is used, as
to leading edge (internal vessel wall) at their maximal dimension ob-
the latter is institution specific.
tained in diastole, when the aortic valve is closed.
tion of measured cardiac dimensions.
The following parameters are included in the comprehensive evaluation for CoA prenatally.
2.1 | Assessment of ventricular dimensions and chamber disproportion
2.5 | Doppler flow patterns Color and spectral Doppler examination is performed at the level of the aortic valve, transverse aortic arch, isthmus, descending aorta, and ductal arch. The aortic valve should demonstrate antegrade flow and
The maximum width of the right ventricle (RV) and left ventricle (LV) is
the velocity time integral and peak velocity recorded. Antegrade flow
measured in the four-chamber (4Ch) view, just below the atrioventric-
by color Doppler throughout the entire aortic arch, isthmus, and de-
ular (AV) valve orifice at end-diastole, when the AV valves are closed
scending aorta as well as right to left shunting across the PDA should
but before the onset of systole. It may also be obtained in the short-
be demonstrated (Figure 2B; Movie S2). A step-up in velocity, con-
axis views, at the level of the papillary muscles. RV predominance is
tinuous flow, or flow reversal across the aortic isthmus all warrant
common in the third trimester, but generally should not exceed an
more detailed evaluation for the possibility of CoA (Figures 3 and 4;
RV:LV ratio >1.5 (Figure 1; Movie S1).
Movies S6 and S7).
2.2 | Assessment of the AV valves
2.6 | Need for serial evaluations
The mitral and tricuspid valve annuli (MV and TV) are evaluated in the
An important echocardiographic predictor for CoA is progression in
four-chamber view, in diastole when the valves are open. Color and
the degree of hypoplasia of the LV and aortic dimensions during serial
pulse Doppler interrogation to assess for stenosis and regurgitation
evaluations. Development of all cardiac structures is highly dependent
is essential.
on adequate blood flow for growth during fetal life. A decrease in the
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(A)
(B)
F I G U R E 2 A. Two-dimensional image of a normal fetal aortic arch as compared to a fetus with transverse arch hypoplasia and coarctation of the aorta: 1—ascending aorta; 2—transverse arch; 3—aortic isthmus. The brachiocephalic vessels are indicated by the arrow. B. Color Doppler imaging illustrates normal prograde laminar flow across the entire aortic arch (blue flow) with no color aliasing suggestive of flow turbulence, continuous diastolic flow, or flow reversal [Colour figure can be viewed at wileyonlinelibrary.com] overall volume ejected from the LV can result in underdevelopment of the aortic arch and CoA. Fetuses with size discrepancy between the RV and LV, aortic arch dimensions that are borderline small, or those with concerning arch configurations or Doppler flow patterns, should be monitored with serial fetal echocardiograms to document interval growth of the left heart structures or progression of the initial findings. The need for frequency and intervals of serial assessment is determined by the nature and severity of the lesion, presence of heart failure, anticipated timing and mechanism of progression, and the options available for prenatal and postpartum intervention.3 Depending on the gestational age at the time of initial suspicion, fetal echocardiograms may be performed every 4–6 weeks, with the last evaluation obtained after 30 weeks. At the very least, one follow-up evaluation in the third F I G U R E 3 Two-dimensional and color Doppler image of an abnormal aortic arch, illustrating flow turbulence at the aortic isthmus. Note the elongated narrowed appearance of the aortic isthmus [Colour figure can be viewed at wileyonlinelibrary.com]
trimester is reasonable to assess for progression of abnormalities or to detect those that may not have been evident on the initial scan. This will enable the clinician to reasonably predict postnatal expectations and plan for delivery.
3 | RED FLAGS THAT RAISE THE SUSPICION FOR COA The prenatal diagnosis of CoA remains a diagnostic challenge. Imaging of the aortic arch during fetal life is often limited by technical difficulties that impair visualization. Furthermore, the normal PDA may make the anatomic narrowing less evident and limits the ability to detect any pressure gradients at the CoA site. Given the challenges of this diagnosis and fears of missing a postnatal CoA, there is often a low diagnostic threshold, which leads to a high false-positive rate. Additional anatomic correlates are often present on fetal echocardiogram and are helpful at improving accuracy of diagnosis. Fetal echocardiographic findings in isolated CoA have been described and are detailed in Table 1.
F I G U R E 4 Color Doppler image of an abnormal aortic arch illustrating retrograde diastolic flow (blue) through the aortic isthmus and distal transverse arch [Colour figure can be viewed at wileyonlinelibrary.com]
3.1 | Ventricular disproportion Ventricular disproportion is most sensitive for coarctation before 25 weeks’ gestation, but is a less reliable indicator in the third
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T A B L E 1 Fetal echocardiographic “red flags” for coarctation of the aorta
3.3 | Great vessel disproportion
Ventricular disproportion
Coarctation of the aorta is very often associated with a discrepancy
RV/LV size discrepancy
in the size of the great vessels,14 with a marked size difference be-
Dilated RV (Z-score >2)
tween the AAo and pulmonary artery (PA). A ratio between the PA
Hypoplastic LV (Z-score 28 weeks’ gestation.17 These size differences likely are a reflection of a redistribution of blood flow secondary to increased resistance in the left ventricular outflow tract with reduced blood flow through the AAo and a compensatory increase in blood flow through the right outflow tract across the PA and PDA in cases of CoA.14,18
Main pulmonary artery/ascending aorta ratio ≥1.7 Abnormal aortic valve Bicuspid or dysplastic Abnormal aortic arch dimensions and anatomy
3.4 | Abnormal aortic valve Abnormal aortic valve morphology (thickened or bicuspid aortic valve)
Aortic isthmus Z-score
