Tiruvarur medical centre, No 5, Javulikara street, Tiruvarur, Tamil Nadu-610001, India.

Following images show a case of aortic coarctation that was seen in a 34-week old fetus.

Images 1, 2: Image 1 shows four-chamber-view of the heart with narrow left ventricle and large right ventricle (right ventricular to left ventricular width ratio is 1.98). Image 2 shows three-vessel-trachea view with tiny aorta and large pulmonary artery.

Images 3, 4: The images show grayscale (image 3) and color Doppler (image 4) scans of the aortic arch with striking narrowing of the aortic isthmus - aortic coarctation.

Images 5, 6: Image 5 shows intact ventricular septum of the heart. Image 6 shows turbulent flow within the aortic root.

Image 7: The image shows bicuspid aortic valve.

Definition

By definition coarctation of the aorta is narrowing of the aortic arch, typically located at the level of aortic isthmus between the left subclavian artery and ductus arteriosus.

Incidence

Coarctation of the aorta makes up about 5% of all congenital heart defects with prevalence of about 4 per 10,000 live births [1, 2].

Prenatal sonographic findings

Prenatal detection of the aortic coarctation is difficult with high rate of false positive and false negative diagnoses [3].

Findings at the level of the four-chamber view of the heart:

Narrow left ventricle in comparison with the right ventricle (right ventricular to left ventricular width ratio 1.69 in coarctation; in normal fetuses the ratio is reported to be about 1.19).

Differential diagnoses - hypoplastic left heart syndrome, interruption of the aorta, physiologic RV/LV size discrepancy after 32 weeks.

Normal ventricular contractility and flow across mitral valve helps to differentiate hypoplastic left heart syndrome. Flow across the aortic arch in color Doppler helps to differentiate interrupted aortic arch.

Three-vessel-trachea view:

Transverse aortic arch is narrow when compared to pulmonary artery (this sign is more specific than ventricular disproportion).

Longitudinal view of the aortic arch:

Power Doppler is preferred mode to examine the longitudinal view of the aortic arch. Narrowing of the isthmus can be demonstrated at the level of the arch, between the left subclavian artery and ductus arteriosus. A tortuosity of the aorta called "shelf sign" can be seen at the junction between ductus arteriosus and descending aorta, and may be a hint to the presence of the coarctation [3] .

Associated cardiac abnormalities:

Ventricular septal defect is the most common associated cardiac abnormality. Bicuspid aortic valve, aortic stenosis at the valvular or subvalvar level, mitral stenosis, multiple left sided cardiac obstructive lesions with the coarctation of the aorta (Shone syndrome), and persistent left superior vena cava are other possible associated cardiac abnormalities [3].

Associated extracardiac abnormalities:

Turner syndrome, and intracranial berry aneurysms [3].

References

1. Hoffman JI, Kaplan S. The incidence of congenital heart disease. J Am Coll Cardiol. 2002 Jun 19;39(12):1890-900. Review. PubMed PMID: 12084585.
2. Reller MD, Strickland MJ, Riehle-Colarusso T, Mahle WT, Correa A. Prevalence of congenital heart defects in metropolitan Atlanta, 1998-2005. J Pediatr. 2008 Dec;153(6):807-13. doi: 10.1016/j.jpeds.2008.05.059. Epub 2008 Jul 26. PubMed PMID: 18657826; PubMed Central PMCID: PMC2613036
3. Alfred Abuhamad Rabih Chaoui ,A practical guide to Fetal Echocardiography,Normal and Abnormal Hearts,Second edition 2010