Coarctation

• Please refer to the suprasternal section for examples of a normal arch.

• Parameterz offers a calculator of z-scores. Click here to access the calculator. 

• More information on coarctation accessible here.

• More of Fetal Coarctation here.

• See the Case of the Month of November 2023, which is on Coarctation of the Aorta

Case 2

Small aortic isthmus measuring 4 mm in diameter. Coarctation. Peak gradient at 42 mmHg into descending aorta by CW-Doppler. Abnormal flow patter in the abdominal aorta with extension of Doppler flow in diastole. 

Case 3

Added October 29, 2023

PDA view outlining that the PDA is closed

View of the arch outlining severe coarctation at the isthmus

Turbulence by Doppler (aliasing) in the context of the acceleration of flow through the obstruction

Measurement of the segment affected, as well as the diamether at the isthmus

Recommendations for measurements of the Aorta

Echocardiographic Assessment of Coarctation and Interrupted Aortic Arch (IAA) - theoretical concepts:

1. Anatomy

Coarctation of the Aorta (CoA)

Coarctation refers to a narrowing or stenosis of the aorta, typically located at or just distal to the left subclavian artery in the juxtaductal region, where the ductus arteriosus attaches. The severity of narrowing can range from mild to severe and may be discrete or involve diffuse arch hypoplasia.

• Potential Causes:

  • Thought to be due to ductal tissue extension into the aorta, which contracts and narrows the lumen.

  • Associated with a small/hypoplastic aortic arch, especially in neonates.

• Associated Cardiac Defects:

  • Bicuspid aortic valve (BAV).

  • Ventricular septal defect (VSD).

  • Single-ventricle defects in more complex cases.

  • Common in Turner syndrome.

Interrupted Aortic Arch (IAA)

IAA is a complete absence of a segment of the aortic arch, classified into three types based on the location of the interruption:

1. Type A: Interruption between the left subclavian artery and the descending aorta. (~30-40% of cases)

2. Type B: Interruption between the left subclavian and left common carotid artery. (~53% of cases, most common).

3. Type C: Interruption between the left common carotid artery and the innominate artery. (~4% of cases, least common).

• Associated Anomalies:

  • DiGeorge syndrome (22q11 deletion) (especially Type B IAA).

  • VSD with subaortic narrowing (posterior malalignment).

  • Truncus arteriosus (especially with PDA).

  • Aortopulmonary window (AP window).

  • DORV-Taussig-Bing anomaly.

  • Small aortic valve (d-malposed aorta).

• Diagnostic Clues for AP Window:

  • High RV pressures due to PDA and/or VSD can obscure typical Doppler findings.

  • Diagnosis relies on anatomic imaging rather than pressure gradients.

2. Pathophysiology

• Coarctation of the Aorta (CoA):

  • Increased left ventricular (LV) afterload due to the narrowing.

  • LV hypertrophy (LVH) may develop or, if severe, the LV may appear dilated and poorly contractile due to pressure overload.

• Interrupted Aortic Arch (IAA):

  • Oxygenated blood from the LV supplies only the proximal aortic arch.

  • The lower body is dependent on ductal flow (PDA) for perfusion.

  • If the PDA closes, severe shock and metabolic acidosis occur due to inadequate systemic circulation.

• Doppler Clues:

  • If the PDA remains open with prostaglandin therapy, the lower body is desaturated, which helps localize the site of the interruption.

  • Diastolic runoff into the PDA from affected brachiocephalic vessels can confirm the site of interruption.

  • In the presence of a VSD, left-to-right shunting increases pulmonary blood flow, leading to LA/LV dilation.

3. Echocardiographic Goals

Coarctation of the Aorta (CoA)

1. Evaluate Aortic Arch Anatomy:

   • Identify aortic arch sidedness.

   • Clearly visualize and document the entire length of the arch in 2D.

   • Measure:

     • LVOT diameter.

     • Aortic root, sinotubular junction (STJ), ascending aorta.

     • Transverse arch, isthmus, and coarctation site (measure at peak systole, inner-to-inner edge).

2. Doppler Evaluation of Aortic Flow:

   • Use color flow, pulsed-wave (PW), and continuous-wave (CW) Doppler in the descending aorta.

   • Measure peak and mean gradients across the coarctation.

   • Obtain PW Doppler in the abdominal aorta from the subcostal sagittal plane.

     • If severe obstruction is present, flow in the descending aorta will be blunted.

3. Assess for Associated Cardiac Defects:

   • Bicuspid aortic valve (BAV).

   • Anomalous subclavian artery.

   • VSD, ASD.

   • Mitral valve abnormalities.

4. Assess LV Function and Afterload:

   • Evaluate LV mass (indexed via M-mode and 2D measurements).

   • Use DTI (Doppler tissue imaging) to assess ventricular strain.

5. Evaluate PDA Status:

   • A closing PDA may worsen obstruction, leading to heart failure.

Interrupted Aortic Arch (IAA)

Diagnostic Clues:

• Suspect IAA in the presence of related defects:

  • VSD with subaortic narrowing (posterior malalignment).

  • Truncus arteriosus with PDA.

  • Aortopulmonary window (AP window).

  • DORV-Taussig-Bing anomaly with d-malposed aorta.

• Arch imaging is critical—missing the typical "candy cane" shape is a key clue.

Echocardiographic Approach:

1. Arch Imaging

   • Use suprasternal notch (SSN) arch view ("candy cane view") to identify the gap between the proximal arch and PDA/descending aorta.

   • If the transverse arch appears to head straight upward, suspect IAA.

2. Determine Aortic Arch Sidedness

   • Use SSN coronal view.

   • Identify the first head vessel posterior to the innominate vein.

   • The arch is contralateral to this first vessel.

   • If the first head vessel bifurcates, it represents the innominate, carotid, and subclavian arteries.

3. Doppler Assessment of Brachiocephalic Arteries

   • Use PW Doppler on each brachiocephalic vessel.

   • Any vessel with diastolic runoff is posterior to the interruption.

4. Patent Ductus Arteriosus (PDA) Evaluation

   • PDA will exhibit right-to-left shunting.

   • Measure PDA size and assess for restriction.

   • Obtain ductal cut views (high parasternal) to visualize the descending aorta and PDA.

   • Use PW Doppler to assess flow direction and restriction.

5. Descending Aorta Flow Analysis

   • Use PW Doppler in the descending abdominal aorta.

   • Flow is often normal but will be blunted if the PDA is closing.

6. Assess for Additional Intracardiac Defects

   • VSD, ASD.

   • Bicuspid aortic valve.

   • Mitral valve abnormalities (e.g., mitral stenosis).