Coarctation of the aorta

Synonym: CoA, aortic coarctation

What is coarctation of the aorta?¹

This is defined as a narrowing of the aorta, usually just distal to the origin of the left subclavian artery, close to the ductus arteriosus/ligamentum arteriosum. It may affect the abdominal aorta very rarely.

It is nearly always a congenital lesion but may very rarely be acquired through trauma causing aortic dissection, reducing the diameter of the true lumen of the aorta.

Coarctation of the aorta is a cause of secondary hypertension and should be considered in its differential diagnosis.

It results in hypertension in the upper body and hypoperfusion of the lower body. Severe cases may present in the neonatal period, or it may go unnoticed and be diagnosed in childhood or later, with the development of collateral circulation of blood to the lower body. It can be particularly problematic for the pregnant woman.

It is often associated with other cardiovascular malformations such as bicuspid aortic valve and ventriculoseptal defect (VSD). It may be associated with another syndrome - eg, Turner syndrome.

Pseudo-coarctation of the aorta is due to excessive tortuosity of the aortic arch, but does not obstruct flow and there is no collateral circulation. It does not usually require active management after diagnosis.

Causes of coarctation of the aorta (embryology)¹

A coarctation of the aorta is a shelf of tissue extending from the postero-lateral aortic wall towards the ductus arteriosus. The shelf is near the patent ductus arteriosus, sometimes above or below it (juxtaductal). A sling of ductus muscle passes around the shelf, and more ductus muscle extends into the aortic wall above and below the shelf. Unlike most other smooth muscle, ductus smooth muscle tends to contract when exposed to high oxygen concentrations.

The arch is often hypoplastic and when present, an associated intracardiac shunt should be suspected. Most often this is an isolated ventricular septal defect, but almost any form of complex congenital heart disease can be associated. About 50 to 70% of the patients have a bicuspid aortic valve. The left subclavian artery is often hypoplastic, and in approximately 5% of these patients arises distal to the shelf.

How common is coarctation of the aorta? (Epidemiology)²

• There are no reliable figures for population incidence, estimated at 1 in 2,500 births.

• It is possibly more common in Caucasians and males.

• Affected parents have a higher risk of the abnormality affecting their child.

• Age at detection is determined by severity and whether there are other associated abnormalities.

Symptoms of coarctation of the aorta (presentation)^{2 3}

Antenatal presentation

It can be diagnosed with ultrasound in utero. However, it is difficult to diagnose antenatally.⁴

Neonatal presentation

• If severe, it usually presents in the first three weeks of life with poor feeding, lethargy, tachypnoea or overt congestive cardiac failure and shock. Initially the baby may be well, depending on whether other anomalies are also present and how long the ductus arteriosus remains patent. However, the infant becomes ill, often abruptly, with closure of the ductus arteriosus. The presence of a VSD will accelerate development of symptoms.

• Pulses may be reduced in amplitude and delayed between upper and lower limbs.

• Blood pressure (BP) is higher in the upper limbs compared with the lower limbs.

• Differential cyanosis can occur with flow across the patent ductus from the right to the left side of the circulation. The upper body appears pink and the legs cyanotic.

• A systolic murmur in the left infraclavicular area is typical but a range of murmurs may be heard depending on collateral circulation and the presence of other cardiac abnormalities.

Late presentation

• Patients are usually asymptomatic and the diagnosis is usually made on examination, prompted often by the presence of, for example, a murmur or hypertension.

• It can cause headache, nosebleeds and leg cramps, particularly with exercise, although claudication is unusual.

• If the left subclavian circulation is affected the left arm may be smaller.

• Lower-limb muscle weakness, cold feet or neurological symptoms in the legs (poor blood supply to the spinal cord) may be the presenting feature.

• There may be physical features of Turner syndrome when associated with this condition.

• Pulses distal to the obstruction are diminished and delayed. Simultaneous palpation of upper and lower limb pulses reveals the clinical hallmark of radiofemoral delay with reduced pulse amplitude in the lower limbs.

• BP may be higher in the upper limbs, but the left arm BP can be normal or low if coarctation involves the origin of the left subclavian artery.

• Auscultation reveals a systolic or continuous murmur, usually heard in the left infraclavicular area and under the left scapula. An ejection click may signify associated bicuspid aortic valve (present in about 85% of cases). A thrill or hum due to flow in aberrant collateral vessels may be present over the chest or abdominal wall.

Association with cerebral aneurysms

• Coarctation of the aorta is associated with berry aneurysms (estimated at approximately 10%).⁵

• These aneurysms can rupture leading to subarachnoid haemorrhage and its complications, including death.

• A subarachnoid haemorrhage can be the presenting feature of coarctation of the aorta.

• There are also case reports of non-aneurysm-related subarachnoid haemorrhage in coarctation of the aorta.⁶

Differential diagnosis

Neonatal disease has a wide differential, including hypoplastic left heart, septal defects and valvular lesions. Coarctation of the aorta may co-exist with many other cardiovascular malformations and expert evaluation is necessary to detect any associated abnormality. The differential diagnosis in adults includes:

• Aortic stenosis.

• Cardiomyopathies (dilated cardiomyopathy and hypertrophic cardiomyopathy).

• Endocardial fibroelastosis.

• Primary hypertension.

• Hypoplastic left heart syndrome.

• Viral myocarditis.

• Circulatory collapse due to hypoadrenalism.

Investigations^{3 7}

Transthoracic echocardiography is mainstay of making initial diagnosis and routine follow-up. Cardiac magnetic resonance imaging (MRI) and computed tomography (CT) are very useful for imaging of the aortic arch in complex cases.⁸

Blood tests

• U&Es, creatinine, FBC, and blood glucose are performed when hypertension is discovered. They are likely to be normal.

• However, when adults or neonates present ill with shock, they should be checked to assess metabolic status and search for other causes of circulatory collapse. Tests in these circumstances will include, for example, arterial blood gases and septic workup (blood cultures along with other specimens for culture).

Imaging

• CXR may show signs of congestive cardiac failure, indentation of aortic shadow at the site of coarctation, or notching on the underside of the ribs due to pressure from collateral blood vessels.

• Echocardiography allows estimation of the pressure gradient caused by the abnormality. This may help in determining severity and the need for intervention. Echocardiography is also used to delineate the coarctation and to help identify any associated abnormalities.

• MRI scan is again used to delineate the nature of the coarctation and any associated abnormalities fully.

ECG

• In adults the ECG usually shows left ventricular hypertrophy and signs of ischaemia (often with strain).

• In neonates the ECG may show initial evidence of right ventricular hypertrophy.

Cardiac catheterisation

• To confirm the diagnosis when this is not clear at ultrasound.

• To determine the gradient across the coarctation (with a gradient in excess of 20 mm Hg considered to be significant).

• To assess other abnormalities and the overall haemodynamic picture when considering therapeutic options in more detail.

• Therapeutically using balloon angioplasty with or without stent implantation.

Management of coarctation of the aorta ^{3 7}

The first surgical repair of aortic coarctation was described in 1944, and since then, several other surgical techniques have been developed and modified. Additionally, transcatheter balloon angioplasty and endovascular stent placement offer less invasive approaches for the treatment of coarctation of the aorta for some patients.

Drug

• Prostaglandin E1 is used in neonates to open the ductus and achieve improved haemodynamic stability when the patient presents acutely.

• Diuretics and inotropes are used to treat congestive cardiac failure affecting neonates and adults alike.

• Beta-blockers are used to treat hypertension in adults before physical correction of the coarctation, and may be used afterwards for persisting hypertension.

• Angiotensin-converting enzyme (ACE) inhibitors and angiotensin-II antagonists may be used alongside beta-blockers to treat post-correction hypertension if the aortic arch obstruction is eliminated.

• Patients are at risk of infective endocarditis and the level of risk is increased if the coarctation is associated with other conditions (for example, bicuspid aortic valve). Guidance on antibiotic prophylaxis has changed and is covered in the separate article Prevention of Infective Endocarditis.

Surgery or balloon angioplasty

Angioplasty, with or without stenting, may be used to correct the coarctation. The decision on which technique to use will depend upon the severity of the coarctation, any associated abnormalities and the acuteness of the presentation.

One small randomised controlled trial (RCT) reported an 86% reduction in peak systolic pressure gradient in both the balloon angioplasty group and the surgery group. A non-randomised study comparing balloon angioplasty with and without stent placement reported a statistically significant reduction in peak systolic gradient of 83% in the angioplasty alone group and 96% in the angioplasty with stent group (p <0.001).⁹

• Surgery has been the standard treatment (for native coarctation and recoarctation) and involves open chest surgery. The surgery used depends on the anatomy of the lesion and preference of the surgeon, but may include resection of the coarctation site and end-to-end anastomosis repair, patch aortoplasty, left subclavian flap angioplasty, or bypass graft repair. More complex lesions require tailored reconstructive approaches.

• Balloon angioplasty and stenting may be carried out as a first treatment (in native coarctation) or if previous surgery or angioplasty fails and coarctation recurs (recoarctation):
  

  • For symptomatic neonates, balloon angioplasty is usually used as a preliminary procedure to buy time before surgery. Outcome appears to be better in neonates following formal reconstructive surgery compared with angioplasty, with fewer complications and better resolution of hypertension.^{10 11}

  • Angioplasty is preferred to treat recurrence of the coarctation following surgery in neonates.¹⁰

  • In adults, balloon angioplasty ± stenting are becoming increasingly favoured. The National Institute for Health and Care Excellence (NICE) has issued guidance on the use of balloon angioplasty ± stenting, compared with surgical reconstruction.⁹ The procedure is considered to be safe in expert multidisciplinary centres, with lower risk of immediate complications such as haemorrhage, but higher rates of later complications such as aneurysm formation and hypertension.

  • Balloon angioplasty ± stenting are becoming increasingly preferred to treat coarctation that recurs after surgery.¹¹

  • An economic analysis suggests that balloon angioplasty is cost-effective as first-line treatment when compared with surgery in children.¹²

Prognosis

Early diagnosis and treatment are important as long-term data consistently demonstrate that patients with coarctation of the aorta have a reduced life expectancy and increased risk of cardiovascular complications.¹³

• If untreated, outlook is poor with less than a fifth surviving beyond the age of 50 years. Even after angioplasty or surgical treatment there are significant morbidity and mortality.¹⁴

• The main determinants of long-term survival include factors such as age at operation and degree and duration of hypertension.

• Long-term follow-up studies have shown mean life expectancy of around 35-38 years of age for those treated in late childhood or early adulthood.^{14 15}

• Principal problems are recoarctation, late aneurysm formation, hypertension and/or premature coronary and cerebrovascular disease.

• Long-term follow-up (with careful monitoring for development of complications and possible ongoing pharmacological therapy) is needed.

• Patients need to avoid excessively vigorous physical activity, contact sports and exercise that involves straining, such as weightlifting. Those with good repair and BP control can improve their outlook by taking regular gentle aerobic exercise.

• Maternal mortality is high (3-8%) in pregnancy, particularly if coarctation is not repaired. However, whether repaired or not, such pregnancies are high-risk.¹¹

Complications of coarctation of the aorta³

• Recoarctation after repair.

• Impaired left ventricular systolic/diastolic function progressing to congestive cardiac failure.

• Thoracic aortic aneurysm.

• Aortic dissection - high risk in pregnancy.

• Cerebral aneurysm rupture - high risk in pregnancy.

• Hypertension.

• Infective endocarditis.

• Paralysis due to spinal cord ischaemia.

• Recurrent laryngeal nerve palsy.

• Endocardial fibroelastosis.

• Hypertrophic cardiomyopathy.

• Postoperative chylothorax due to thoracic duct damage.

• Postoperative mesenteric arteritis due to sudden increase in visceral perfusion (post-coarctectomy syndrome).

Prevention

The condition may be suggested by prenatal ultrasound scanning but is difficult to detect.⁴ It may be suspected when there is unexplained enlargement of the right ventricle, difficulty identifying the aortic arch or the presence of other frequently associated anomalies.

Early detection after birth is important to avoid complications. Careful screening of babies at the newborn examination is very important.