Coarctation of the Aorta: Pathophysiology, Clinical Features, Diagnosis, Management

Coarctation of the Aorta

~Introduction

Coarctation of the aorta (CoA) is a congenital cardiovascular defect characterized by the narrowing of the aortic lumen, which leads to obstruction of blood flow from the left ventricle to the systemic circulation. This condition accounts for approximately 5–8% of all congenital heart diseases and is more common in males than females, with a male-to-female ratio of about 2:1. The narrowing typically occurs just distal to the origin of the left subclavian artery, near the site of the ductus arteriosus, in the region known as the aortic isthmus.

The condition can present in various forms, ranging from mild cases that remain undetected until adulthood to severe neonatal presentations associated with heart failure and shock. Coarctation of the aorta has significant implications for systemic blood pressure regulation, cardiac workload, and long-term cardiovascular health if untreated.

~Normal Anatomy of the Aorta

The aorta is the main artery that carries oxygenated blood from the left ventricle of the heart to the rest of the body. It has several segments:

1. Ascending Aorta – arises from the left ventricle and gives rise to the coronary arteries.

2. Aortic Arch – curves posteriorly and gives rise to three major branches:

   • Brachiocephalic trunk

   • Left common carotid artery

   • Left subclavian artery

3. Descending Thoracic Aorta – continues downward, supplying the thoracic wall and visceral organs.

4. Abdominal Aorta – supplies the abdominal organs and bifurcates into the common iliac arteries.

In coarctation, the narrowing usually occurs in the descending thoracic aorta, distal to the origin of the left subclavian artery.

~Pathophysiology

Coarctation of the aorta produces an obstruction to left ventricular outflow, causing an increased afterload. The left ventricle must generate higher pressure to overcome the resistance caused by the narrowed segment, leading to left ventricular hypertrophy (LVH).

Blood pressure proximal to the narrowing (upper body and arms) becomes elevated, while pressure distal to the coarctation (lower body and legs) is reduced. Over time, collateral circulation develops through the intercostal, internal thoracic, and scapular arteries to bypass the obstruction. These collateral vessels can become dilated and tortuous, sometimes eroding the undersurface of the ribs—a classic radiologic sign.

Depending on the severity of narrowing, the condition can lead to systemic hypertension, cardiac failure, aortic rupture, or intracranial hemorrhage if left untreated.

~Etiology and Embryology

Congenital Causes

The exact embryologic mechanism is not completely understood, but several theories have been proposed:

• Ductal tissue theory: Suggests that ductal tissue extends into the aortic wall. When the ductus arteriosus closes after birth, it constricts the adjacent aortic wall, producing a coarctation.

• Hemodynamic theory: Abnormal blood flow during fetal life leads to underdevelopment of the aortic segment, resulting in narrowing.

Associated Conditions

Coarctation often occurs in association with other congenital cardiac anomalies, including:

• Bicuspid aortic valve (most common, in 50–85% of cases)

• Ventricular septal defect (VSD)

• Patent ductus arteriosus (PDA)

• Mitral valve anomalies

• Turner syndrome (45,X karyotype) – where coarctation is a common cardiovascular defect

• Shone complex – a combination of left-sided obstructive lesions

~Classification

Coarctation of the aorta can be classified based on the relationship to the ductus arteriosus:

1. Preductal (Infantile Type):

   • The narrowing occurs proximal to the ductus arteriosus.

   • Blood flow to the descending aorta is often dependent on a patent ductus arteriosus (PDA).

   • Typically presents in neonates with severe symptoms and heart failure once the PDA closes.

2. Postductal (Adult Type):

   • The narrowing occurs distal to the ductus arteriosus.

   • Often presents later in childhood or adulthood with hypertension and differential pulses between upper and lower limbs.

~Clinical Features

Neonatal Presentation

In severe preductal coarctation, the neonate may appear healthy at birth but deteriorates rapidly when the ductus arteriosus closes. Symptoms include:

• Tachypnea and dyspnea

• Poor feeding

• Lethargy

• Pallor or cyanosis (especially of lower body)

• Oliguria or anuria (due to renal hypoperfusion)

• Signs of congestive heart failure and shock

Childhood and Adult Presentation

In less severe or postductal forms, symptoms may not appear until later in life:

• Headaches and epistaxis due to upper body hypertension

• Leg fatigue or cramps during exercise due to poor lower body perfusion

• Cold feet and delayed wound healing

• Differential cyanosis (in cases associated with PDA)

• Weak or delayed femoral pulses (radio-femoral delay)

Physical Examination Findings

• Blood Pressure Difference: Higher in arms than legs (systolic gradient >20 mmHg)

• Pulse Delay: Delayed femoral pulse compared to radial pulse

• Cardiac Murmur: Systolic murmur best heard over the left infrascapular area or left upper sternal border

• Collateral Circulation: May cause continuous murmurs over the chest or back

• Left Ventricular Heave: Due to hypertrophy

~Diagnosis

1. Blood Pressure Measurement

A marked difference between upper and lower extremity pressures suggests coarctation. Normally, leg pressures are slightly higher, but in CoA, upper extremity pressure is significantly elevated.

2. Chest X-Ray

• “Figure 3 sign” – due to pre- and post-stenotic dilatation of the aorta

• Rib Notching – seen in older children and adults due to enlarged intercostal arteries eroding the undersurface of ribs

• Cardiomegaly – if heart failure is present

3. Electrocardiogram (ECG)

• Left ventricular hypertrophy (LVH) is common.

• Neonates may show right ventricular hypertrophy if pulmonary hypertension coexists.

4. Echocardiography

• The primary diagnostic tool for infants and children.

• Demonstrates the site and severity of coarctation.

• Assesses associated cardiac anomalies such as bicuspid aortic valve or VSD.

5. MRI and CT Angiography

• Provide detailed visualization of the aorta and collateral vessels.

• Useful in preoperative planning and postoperative follow-up.

6. Cardiac Catheterization

• Used when non-invasive imaging is inconclusive or when intervention is planned.

• Measures pressure gradients across the coarctation site.

~Differential Diagnosis

Conditions that may mimic CoA include:

• Takayasu arteritis (especially in young women)

• Supravalvular aortic stenosis

• Peripheral arterial disease

• Interrupted aortic arch

• Mid-aortic syndrome

~Management

Treatment aims to relieve the obstruction, normalize blood pressure, and prevent complications. The choice of therapy depends on age, anatomy, and severity.

1. Medical Management (Initial Stabilization)

• In neonates with critical coarctation, Prostaglandin E1 infusion is given to maintain ductal patency and ensure systemic perfusion.

• Inotropes (e.g., dopamine, dobutamine) to support cardiac output.

• Diuretics and oxygen therapy for congestive heart failure.

• Antihypertensive therapy (beta-blockers, ACE inhibitors) pre- and postoperatively.

2. Surgical Management

Surgery is the treatment of choice, especially in infants and young children.

Surgical Techniques:

• Resection with End-to-End Anastomosis: Removal of the narrowed segment with direct rejoining of aortic ends (most common approach).

• Subclavian Flap Aortoplasty: The left subclavian artery is used to enlarge the narrowed area.

• Patch Aortoplasty: Enlargement using a synthetic patch.

• Interposition Graft: Replacement of the narrowed section with a graft.

3. Catheter-Based Intervention (Balloon Angioplasty & Stenting)

• Balloon Angioplasty: Used for recurrent or discrete coarctations, especially in older children or adults.

• Stent Placement: Effective in adolescents and adults to prevent elastic recoil and restenosis.

~Complications

Even after successful repair, patients remain at risk for several complications:

1. Re-Coarctation: Re-narrowing at the repair site, particularly in infants.

2. Aneurysm Formation: At or near the repair site, potentially leading to rupture.

3. Persistent Hypertension: Despite anatomical correction.

4. Aortic Dissection or Rupture

5. Endarteritis or Endocarditis

6. Cerebrovascular Events: Due to long-standing hypertension.

7. Premature Coronary Artery Disease

~Long-Term Follow-Up

Patients with repaired coarctation require lifelong surveillance, including:

• Annual blood pressure monitoring in both arms and legs.

• Periodic echocardiography or MRI to detect re-coarctation or aneurysm.

• Management of hypertension with beta-blockers, ACE inhibitors, or ARBs.

• Endocarditis prophylaxis in high-risk cases.

• Counseling regarding physical activity—competitive sports may be restricted until postoperative evaluation confirms normal gradients.

~Prognosis

Without treatment, the natural history of coarctation is poor—most patients die by the fourth decade of life due to complications like heart failure, aortic rupture, or intracranial hemorrhage.
However, with early diagnosis and appropriate surgical or interventional treatment, long-term survival exceeds 90%, and quality of life is excellent. Persistent hypertension remains the most common late complication, emphasizing the need for lifelong follow-up.

~Recent Advances

Recent developments in imaging, interventional cardiology, and surgical techniques have significantly improved outcomes:

• 3D echocardiography and MRI enhance preoperative planning.

• Covered stents reduce the risk of aneurysm formation during angioplasty.

• Hybrid approaches combining surgery and catheter-based interventions are increasingly employed in complex cases.

Gene studies and fetal echocardiography also aid in early detection, particularly in syndromic cases such as Turner syndrome.

~Conclusion

Coarctation of the aorta represents a critical yet treatable congenital cardiovascular anomaly. Timely diagnosis and intervention are vital to prevent long-term complications such as hypertension, heart failure, and cerebrovascular disease. Advances in imaging, surgical, and catheter-based therapies have transformed outcomes, allowing affected individuals to lead healthy, productive lives with appropriate follow-up and blood pressure control. Despite successful repair, vigilance for recurrence and secondary hypertension remains essential throughout life.