Makindo Medical Notes

Related Subjects: |Aortic Anatomy |Acute Coronary Syndrome (ACS) General |Aortic Dissection |Acute Heart Failure and Pulmonary Oedema |Aortic Regurgitation (Incompetence) |Aortic Stenosis |Aortic Sclerosis |Transcatheter aortic valve implantation (TAVI)

Coarctation of the aorta typically occurs just distal to the origin of the left subclavian artery, leading to higher blood pressure in the arms compared to the legs (opposite of the normal situation). Blood pressure should always be measured in the legs as well as both arms due to this gradient. Weaker pulses are found in the lower extremities compared to the upper extremities. Intercostal collaterals may produce bruits on examination and cause rib notching on chest radiographs. Coarctation can be treated with surgical repair or balloon angioplasty with stenting.

About

• Definition: Coarctation of the Aorta (CoA) is a congenital narrowing of the aorta, typically at or just distal to the left subclavian artery.
• Prevalence: Accounts for about 5% of all congenital heart diseases.
• Nature: Often involves a generalized aortopathy, which means the aorta may have areas of stiffness and reduced compliance.

Associations

• Gender: More common in males (2-5 times) compared to females.
• Genetic Conditions: Frequently associated with Turner syndrome.
• Bicuspid Aortic Valve: Present in approximately 50% of patients with CoA.
• Berry Aneurysms: Increased risk of intracranial aneurysms and subarachnoid hemorrhage (SAH).

Aetiology and Pathophysiology

• Anatomical Defect: CoA is usually caused by a shelf-like or ridge-like narrowing within the aortic arch, typically distal to the left subclavian artery, but it can occur anywhere along the descending aorta.
• Haemodynamic Effects: The narrowing creates a pressure gradient across the constriction, leading to increased pressure proximal (above) and decreased pressure distal (below) the coarctation site.
• Collaterals: Extensive collateral circulation develops through the intercostal arteries to bypass the obstruction, which can cause rib notching on imaging.
• Aortic Stiffness: The aorta in patients with CoA may be stiff and non-compliant, contributing to long-term risks of hypertension even after repair.

Clinical Presentation

• Infants: Severe CoA can present with heart failure in infancy, especially if the ductus arteriosus closes early.
• Children and Adults: Often present with:
  • Upper body hypertension, headaches, and nosebleeds.
  • Weak or delayed femoral pulses (radial-femoral delay).
  • Cold legs or feet due to reduced circulation to the lower extremities.
  • A continuous or systolic murmur between the shoulder blades due to turbulent flow through the narrowed segment.
  • Exercise intolerance and leg claudication in older children and adults.
• Complications: Increased risk of aortic dissection, heart failure, and premature coronary artery disease.

Investigations

• Basic Bloods: FBC, U&E, LFTs for general health assessment.
• ECG: Left ventricular hypertrophy (LVH) due to increased afterload.
• Echocardiography: Useful for evaluating the extent of LV hypertrophy, identifying bicuspid aortic valves, and visualizing the site and severity of the coarctation.
• Chest X-ray: Shows the "reversed 3" sign or "figure 3" sign due to pre- and post-stenotic dilation, as well as rib notching from dilated collateral intercostal arteries.
• MRI/MRA or CT Angiography: Preferred in older children and adults for detailed visualization of the coarctation and collateral vessels.
• Cardiac Catheterization: May be used for hemodynamic assessment, measuring pressure gradients across the coarctation (significant if >20 mmHg).

Complications

• Post-repair Complications: Risk of aortic aneurysms at the site of repair, and re-coarctation, especially in younger children.
• Long-term Risks: Hypertension, even after successful repair, due to altered baroreceptor response and persistent aortic stiffness.
• Aortic Valve Disease: Increased incidence of aortic stenosis or regurgitation, especially if associated with a bicuspid aortic valve.
• Coronary Artery Disease: Premature atherosclerosis can develop due to chronic hypertension.

Management

• Medical Management:
  • Control hypertension with beta-blockers, ACE inhibitors, or ARBs, especially in the pre- and post-operative period.
  • Monitor and manage heart failure symptoms in infants with severe coarctation.
• Surgical Repair: Indicated for significant coarctation with a pressure gradient >20 mmHg or symptoms. Techniques include resection with end-to-end anastomosis, patch aortoplasty, or subclavian flap repair.
• Balloon Angioplasty and Stenting: A less invasive option that can be performed as primary treatment or for recurrent coarctation after surgery. It is particularly useful in older children and adults.
• Long-term Follow-up: Regular follow-up is essential to monitor for re-narrowing, persistent hypertension, or development of aneurysms. Annual or biannual echocardiograms and blood pressure monitoring are standard.

Long-term Risks

• Neurological Risks: Higher risk of berry aneurysms and subsequent subarachnoid hemorrhage (SAH), which requires screening with brain imaging.
• Hypertension: Persistent hypertension even after repair, due to changes in aortic compliance and baroreceptor function.
• Aortic Dissection: Increased risk, particularly in young adults, due to weakened aortic walls.
• Coronary Artery Disease: Early-onset coronary atherosclerosis is common, necessitating aggressive management of risk factors.