Coarctation and Interrupted Aortic Arch

• 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

Review of Concepts related to Coarctation of the Aorta

Coarctation of the aorta (CoA) is a congenital cardiovascular anomaly characterized by a narrowing of the aortic lumen. This narrowing is typically located just beyond the origin of the left subclavian artery at the site where the ductus arteriosus inserts ("Isthmus"). CoA is considered a common congenital heart lesion, accounting for 4–7% of all congenital heart defects and approximately 4 per 10,000 births. It shows a male predominance.

Pathophysiology and Presentation in Neonates

In the neonatal period, the clinical presentation of CoA is highly variable, depending largely on the severity of the narrowing and the status of the ductus arteriosus (PDA). The narrowing creates an obstruction to blood flow. With severe CoA, adequate blood flow to the lower body is dependent on blood shunting from the pulmonary artery to the descending aorta through the patent ductus arteriosus. This makes severe CoA a critical congenital heart defect that is ductal-dependent for systemic flow. When the ductus arteriosus begins to constrict and close after birth (typically within the first 1 to 2 weeks of life), the obstruction at the coarctation site becomes manifest and can significantly impede systemic blood flow. This sudden increase in afterload on the left ventricle (LV) can lead to left ventricular dysfunction and shock. Collateral circulation is not developed at birth, so it cannot compensate for the obstruction in acutely presenting neonates. 

Left-sided obstructive lesions (such as hypoplastic left heart syndrome, coarctation of the aorta, interrupted aortic arch, or aortic/LVOT stenosis) that are ductal-dependent should always be high on the differential diagnosis in neonates who experience acute decompensation following a period of relative postnatal stability. The differential diagnosis should include septic shock, metabolic disorders, non-accidental trauma (e.g., shaken baby syndrome), and ductal-dependent congenital heart disease, among others. Other reasons for a decompensating newborn could include: Myocarditis or neonatal cardiomyopathy; Severe arrhythmias (e.g., supraventricular tachycardia, complete AV block); Acute neurologic events (e.g., seizures, intracranial hemorrhage); Adrenal crisis (e.g., congenital adrenal hyperplasia); Severe anemia, polycythemia, or blood loss; Inborn errors of metabolism presenting with encephalopathy or acidosis; Tension pneumothorax or severe pulmonary disease (e.g., pneumonia, aspiration), tamponade. Also think of you Hs & Ts (Hypoxia, Hypovolemia, Hydrogen ion (acidosis), Hypoglycemia, Hypothermia, Hyper/hypokalemia, and Tamponade (cardiac), Tension pneumothorax, Thrombosis (pulmonary or coronary), Toxins, and Trauma).

Neonates with severe CoA often present with symptoms of heart failure, including poor feeding, irritability, respiratory distress, and lethargy. They may present in extremis with cardiogenic shock. Key physical findings include weak or absent femoral pulses compared to brachial pulses, and a significant blood pressure gradient between the upper and lower extremities, with upper limb hypertension. A continuous murmur with systolic accentuation, often loudest over the back, may be present, although in low cardiac output, a murmur might be absent. Hepatomegaly may also develop with cardiac failure. Less severe coarctations may be asymptomatic for a longer period, presenting later in infancy or childhood with findings like hypertension.

Associated Conditions

CoA in neonates is frequently associated with other congenital heart defects. Common associations include: Bicuspid aortic valve (BAV), Ventricular septal defect (VSD), Patent ductus arteriosus (PDA) (often present at presentation, making it "duct-dependent"), Aortic valvular stenosis (AS), Aortic arch hypoplasia (of various degree), and less commonly, Interrupted Aortic Arch (IAA) (which is a more severe spectrum). CoA is also associated with genetic syndromes, notably Turner syndrome (in about 30% of cases) and, less frequently than IAA, DiGeorge syndrome (22q11.2 deletion).

Hemodynamics in perspective: A patient with a Coarctation and an atrial septal defect may be significantly more symptomatic than one with only a coarctation. Since the coarctation creates high resistance on the left side, the left ventricle may become stiffer (less compliant). Because atrial shunting is compliance-driven, the reduced LV compliance promotes shunting from the left atrium to the right atrium. This results in increased blood flow to the right side of the heart, increased QP (pulmonary blood flow) through two separate shunts (ASD and a PDA that is artifically maintained and may be bidirectional), and potentially severe lung congestion, compounded by reduced systemic cardiac output.

In coarctation, pre-ductal (right arm / ascending aorta) diastolic pressure best reflect coronary perfusion, because coronaries arise from the ascending aorta. If the LV begins to fail due to the high afterload (high pre-ductal pressure), the LVEDP will rise. If the pre-ductal diastolic pressure is too low, the coronary perfusion pressure / "driving pressure" into the coronaries becomes inadequate, leading to a vicious cycle of myocardial ischemia and further LV dysfunction - more on coronary perfusin pressure here.

Diagnosis

A high index of suspicion is crucial for diagnosing CoA in infants presenting with circulatory collapse.

• Clinical Evaluation: Assessment of peripheral pulses (especially femoral vs. brachial) and measurement of blood pressure in upper and lower limbs are fundamental.

• Echocardiography (see below for more details on echocardiography assessments): This is the primary diagnostic tool and the gold standard in neonates and infants. Echocardiography allows visualization of the aortic arch anatomy, including the site and severity of the narrowing, which often appears as a posterior "shelf". It can assess the size of the aortic arch segments, the morphology of the aortic valve (e.g., bicuspid), and the presence of associated intracardiac anomalies like VSD or atrial septal defect (ASD). Doppler flow studies can evaluate flow patterns and velocities across the coarctation site (typically high-velocity systolic flow with diastolic decay) and in the descending aorta (often a damped or flat profile with severe obstruction). Fetal echocardiography can suspect or diagnose CoA antenatally. Notably, the diagnosis might be missed in neonates with a large, widely patent PDA until the duct begins to close. Colour Doppler flow at the coarctation is often highly suggestive, showing systolo-diastolic prolongation (continuous flow, not just systolic). In severe coarctation with no PDA, the flow in the abdominal aorta can be very low (<40 cm/s) and almost venous-like (non-pulsatile), indicating poor perfusion of the descending aorta.

  • Of note, Doppler gives instantaneous peak gradient; cuff/line comparison is peak-to-peak and location-dependent. With PGE and a PDA, ductal flow can partially “bypass”/equalize descending aortic pressure, reducing the measured arm–UAC gradient. UAC position (low), damping/line factors, and changing flow patterns (R→L in systole) also affect measured gradients.

  • The primary reason for the discrepancy between a Doppler gradient and a blood pressure gradient (pre- and post-ductal limb) is the distinction between maximum instantaneous gradients and peak-to-peak gradients,. Doppler echocardiography uses the modified Bernoulli equation (4V 2 ) to calculate the maximum instantaneous gradient, which is the pressure difference between two points at the exact moment the blood reaches its highest velocity,. Conversely, the peak-to-peak gradient, typically measured via cardiac catheterisation or limb BP cuffs, represents the numerical difference between the absolute peak systolic pressure in the proximal aorta and the absolute peak systolic pressure in the distal aorta,. These two peak pressures do not occur simultaneously during the cardiac cycle; because the peak pressure in the proximal segment occurs before the peak pressure in the distal segment, the peak-to-peak value is mathematically smaller than the maximum instantaneous value measured by Doppler,,. Another significant factor is the pressure recovery phenomenon. As blood flow accelerates through the narrow coarctation, its kinetic energy (velocity) increases while its potential energy (pressure) drops,. Doppler measures the pressure at the point of maximum velocity, but as the blood continues downstream into a wider area, the flow slows down, and some of that kinetic energy is converted back into potential energy (pressure),. A distal BP measurement—such as one taken from the leg—captures the pressure after this recovery has occurred, which results in a smaller measured gradient compared to the initial drop at the site of the obstruction,. Furthermore, the BP gradient between limbs is affected by peripheral systolic amplification. In the systemic arterial tree, systolic pressure naturally increases as the pressure wave travels farther from the heart toward the extremities due to the interaction of reflected waves. This means the BP measured in the right arm (pre-ductal) may be significantly higher than the central aortic pressure, especially in children with reactive arteries or in vasoconstricted states like heart failure,. While Doppler focuses strictly on the site of the coarctation, limb BP gradients incorporate these peripheral wave dynamics, which can vary based on systemic vascular resistance and the degree of collateral circulation,. Finally, clinical conditions such as sedation during catheterisation or the use of mechanical ventilation can lower the measured invasive gradients compared to those obtained in an awake, physiologically stressed infant during an echocardiogram,. Because of these various factors, the Doppler-derived gradient is generally expected to be approximately 20% higher than the peak-to-peak gradient.

• Other Imaging: Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) are sometimes used for detailed delineation of aortic arch anatomy, particularly for surgical planning, but echocardiography is usually sufficient and preferred for initial diagnosis in this age group.

• Cardiac Catheterization: Rarely needed for diagnosis alone in the current era, but used for interventions like balloon angioplasty.

Management

Initial management in neonates presenting with severe symptoms or shock is focused on stabilization.

• Immediate cardiorespiratory support is initiated.

• Prostaglandin E1 (PGE1) infusion is critical to reopen or maintain the patency of the ductus arteriosus, restoring systemic blood flow to the lower body. PGE1 can also potentially relax tissue at the coarctation site.

• Medical support may help improve LV function.

• In neonates with duct-dependent systemic circulation (like severe CoA, HLHS, IAA), avoiding supplemental oxygen is advisable as it can cause the ductus arteriosus to constrict, worsening the obstruction. However, this is unlikely to occur with PGE1 infusion, but O2 is a pulmonary vasodilator and will "steal" from the flow that must be sent to the systemic circulation. As such, in presence of oxygen, the PVR/SVR ratio may not favour the necessary right to left shunt towards the systemic circulation.

Definitive treatment typically involves surgical repair in neonates and young infants. Techniques include extended end-to-end anastomosis, which is currently preferred due to lower rates of re-coarctation compared to older methods.

Outcomes and Long-Term Implications

Short-term outcomes with timely surgical repair are generally excellent. However, CoA is a lifelong condition, and lifelong follow-up is mandatory. Patients remain at risk for long-term complications, including recoarctation, formation of aortic aneurysms, and importantly, persistent systemic hypertension, even after anatomically successful repair.

Understanding the unique pathophysiology and presentation of CoA in the neonatal period, and leveraging echocardiography for accurate and timely diagnosis, are fundamental aspects of providing optimal care for these vulnerable patients.

Etiology

The exact cause (etiology) of aortic coarctation is not completely understood. Associated factors:

1. Abnormal Ductal Tissue: It is attributed to the abnormal extension or ingrowth of tissue from the wall of the ductus arteriosus (PDA) into the aortic wall at the site of arterial duct insertion. Histologically, the ductus arteriosus has different muscle fibers (longitudinally and spirally arranged) and a thick, irregular intima with intimal cushions compared to the aorta's circumferentially arranged elastic fibers. Following birth, when the ductus arteriosus constricts and closes (triggered by increased arterial oxygen levels), this misplaced ductal tissue within the aortic wall also contracts and can progressively narrow the aortic lumen. If not treated in infancy, intimal growth over time can worsen the narrowing. This theory, sometimes called the "ductal tissue theory" or Skodaic hypothesis, is supported by histological findings of ductus tissue extending into the aortic wall and the fact that the obstruction often isn't evident in utero but develops after birth with ductal closure. The posterior aortic shelf seen in CoA is often continuous with the muscular tissue of the arterial duct wall.

2. Hemodynamic Factors / Flow-Related Lesion: This theory, known as the "form follows flow" theory, suggests that abnormalities decreasing the antegrade blood flow across the aortic isthmus during fetal development lead to failure of the isthmus to grow, resulting in hypoplasia and coarctation. This is particularly relevant in cases where CoA is associated with other congenital heart defects (like VSDs, aortic stenosis, mitral valve abnormalities, Shone complex, or Hypoplastic Left Heart Syndrome), where upstream obstructions or shunting patterns can impair fetal blood flow through the left ventricular outflow tract and ascending aorta. For example, abnormalities encouraging flow into the pulmonary pathway rather than the aortic pathway during fetal life are frequently associated with coarctation. Increased flow through the ductus arteriosus and decreased flow through the aortic isthmus can make the junction of these two vessels act as an exaggerated branch point, contributing to the formation of the aortic shelf characteristic of coarctation.

3. Embryological Disturbances: Beyond the ductal tissue theory, other primary embryological disturbances have been considered. One relates to the migration of the left seventh intersegmental artery (which forms the left subclavian artery). However, there is no evidence to support this as a cause, and it's equally possible another factor causes both. Abnormalities in endothelial rearrangement, as suggested by studies in zebrafish, might also play a role in forming the obstruction.

4. Genetic Factors: CoA is frequently seen in patients with Turner syndrome (45,X or 45,XO), suggesting a genetic predisposition. Karyotype screening is recommended for females diagnosed with CoA. About half of patients with Turner syndrome who have congenital heart disease have CoA. Mutations in specific genes, such as NOTCH1, have been identified and associated with left-sided obstructive lesions, including CoA. NOTCH1 is important for endothelial cell development and migration. There is an increased risk for first-degree relatives of individuals with obstructive left-sided heart lesions. CoA is also associated with DiGeorge syndrome (chromosomal deletion in 22q11), although this deletion is much more frequently associated with Interrupted Aortic Arch, particularly Type B.

Vital signs (shared by Dr Michael-Andrew Assaad): Marked pre-ductal hypertension (92/58 mmHg) with a large pre-/post-ductal blood pressure gradient (post-ductal 53/22 mmHg), consistent with coarctation in the setting of a restrictive ductus arteriosus. On pulse oximetry, the pre-ductal limb shows a markedly higher waveform amplitude (pulsatility), whereas the lower limbs demonstrate a low-amplitude signal, reflecting altered distal perfusion.

Prolonged diastolic tail / Diastolic Extension

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

Case 4

Added December 3rd, 2025

Case 4

Added December 7, 2025

Case 6

Added December 7, 2025

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)

   1. Berry Syndrome: This is a specific, rare combination of cardiovascular anomalies that includes IAA (usually Type A), a distal AP window, and an intact ventricular septum, along with the origin of the right pulmonary artery from the ascending aorta.

   2. While exceedingly rare, an IAA with an intact ventricular septum (IVS) can occur (most often seen in Type A interruptions). In these cases, the fetal RV still successfully perfuses the descending aorta via the DA without any ventricular-level shunt.

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).

Beyond these primary types, variations can exist, including the persistence of a fibrous cord connecting the segments or a total absence of development in the interrupted segment.

• 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.

4. 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).

Classification of Interrupted Aortic Arch

Celoria and Patton - 1959

References

• Dipchand AI, et al., editors. Manual of Cardiac Care in Children. Springer Nature Switzerland AG; 2024. ISBN: 978-3-031-70973-9. DOI: 10.1007/978-3-031-70973-9. https://doi.org/10.1007/978-3-031-70973-9.

• Law MA, Collier SA, Sharma S, et al. Coarctation of the Aorta. [Updated 2024 Dec 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Bookshelf ID: NBK430913. PMID: 28613663. https://www.ncbi.nlm.nih.gov/books/NBK430913/.

• Coarctation: A Review. US Cardiology Review. 2019;13(2):99–104. DOI: https://doi.org/10.15420/usc.2019.15.2.

• Park IS, editor. An Illustrated Guide to Congenital Heart Disease: From Diagnosis to Treatment – From Fetus to Adult. Springer Nature Singapore Pte Ltd.; 2019. ISBN: 978-981-13-6977-3 (Print), 978-981-13-6978-0 (eBook). DOI: 10.1007/978-981-13-6978-0. https://doi.org/10.1007/978-981-13-6978-0.

• Rudolph AM. Congenital Diseases of the Heart: Clinical-Physiological Considerations. 3rd ed. John Wiley & Sons, Ltd. / Wiley-Blackwell; 2009. ISBN: 978-1-405-16245-6. https://onlinelibrary.wiley.com/doi/book/10.1002/9781444301549.

• Salciccioli KB, Zachariah JP. Coarctation of the Aorta: Modern Paradigms Across the Lifespan. Hypertension. 2023;80(10):1970-1979. DOI: 10.1161/HYPERTENSIONAHA.123.21102. PubMed ID: 37476999.

• Celoria, Guillermo C., and Roy B. Patton. "Congenital absence of the aortic arch." American heart journal 58.3 (1959): 407-413.

• Van Mierop LH, Kutsche LM. Interruption of the aortic arch and coarctation of the aorta: pathogenetic relations. Am J Cardiol. 1984 Oct 1;54(7):829-34. doi: 10.1016/s0002-9149(84)80215-5. PMID: 6486034.