Pediatrics

Coarctation of the aorta

OVERVIEW: What every practitioner needs to know

Are you sure your patient has coarctation of the aorta? What are the typical findings for this disease?

The hallmark examination finding is decreased femoral pulses. More specifically, this is a discrepancy of the strength and timing of the upper extremity pulses compared with lower extremity pulses. This is because the most typical location of the coarctation is after the subclavian arteries.

Usually children with coarctation of the aorta outside of infancy are asymptomatic.

Hypertension in the upper extremities (above the obstruction) with decreased blood pressure in the lower extremities (below the obstruction) supports the diagnosis of coarctation of the aorta. The severity of obstruction may not be directly related to the degree of hypertension or the magnitude of blood pressure difference between the upper and lower extremities. Coarctation is felt to be the most common curable cause of hypertension in pediatrics.

Severe coarctation in the neonate usually presents after closure of the ductus arteriosus. A neonate with coarctation may present in cardiogenic shock with poor cardiac output and respiratory distress.

Coarctation of the aorta can be associated with other significant congenital heart defects. For the purposes of this chapter we will consider only isolated, discrete coarctation of the aorta.

Physical Examination Findings

Coarctation in the neonate usually presents within the first 2 weeks of life. Clinical symptoms occur with narrowing or closure of the ductus arteriosus and an acute increase in systemic vascular resistance (afterload) leading to heart failure. The neonate can have a clinical picture consistent with cardiogenic shock and respiratory distress:

Tachypnea

Retractions

Grunting

Poor global perfusion

Absent femoral pulses

Tachycardia

Hypotension

The electrocardiogram (ECG) in neonates with isolated coarctation usually suggests right ventricular hypertrophy or a right bundle branch block pattern. The chest radiograph can demonstrate cardiomegaly and pulmonary venous congestion.

Most children with coarctation of the aorta after infancy are asymptomatic. Usually the diagnosis is made during an evaluation for hypertension. Decreased or absent femoral pulses compared with simultaneous brachial palpation is essentially pathognomonic for coarctation.

Older patients may have several different murmurs on examination. There may be a systolic ejection murmur in the left infraclavicular, axillary, or intrascapular region of the back. Additional continuous murmurs may be heard in the chest and back secondary to development of significant collateral vessels. Up to 75% of patients with coarctation have a bicuspid aortic valve. An ejection click and/or systolic ejection murmur due to the bicuspid valve and aortic stenosis may be heard. Hypertension with a discrepancy in the upper to lower extremities is diagnostic of coarctation. There are rare circumstances in which the subclavian arteries may have anomalous origins at or below the obstruction and therefore all four extremity blood pressure measurements will be equal and low.

The ECG in patients after infancy can be normal but usually has increased voltages in the left precordial leads (left ventricular hypertrophy.) Chest radiography can demonstrate a prominent aortic knob.

The classic finding of "rib notching" is due to dilated intercostal arteries eroding into the ribs. This pathognomonic finding increases with age and is not usually present in young children.

What other disease/condition shares some of these symptoms?

A neonate with complex congenital cardiac conditions that have ductal dependent systemic blood flow can present in extremis as the ductus arteriosus closes. These defects include critical aortic stenosis, severe coarctation of the aorta, aortic atresia, interrupted aortic arch, and hypoplastic left heart syndrome. Other noncardiac conditions that can have a similar neonatal presentation are neonatal myocarditis with severe heart failure, various inborn errors of metabolism, and sepsis.

Outside the neonatal period, other causes of hypertension, for example, renovascular causes can have symptoms similar to those of coarctation. Middle aortic syndrome is a rare entity with segmental stenosis or narrowing of the distal descending aorta, which can present with hypertension and altered femoral pulses.

What caused this disease to develop at this time?

Ductal closure leads to the timing and severity of clinical presentation in the neonate.

Regardless of timing of presentation (neonatal period or after the neonatal period), coarctation of the aorta is a congenital defect.

What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?

Coarctation of the aorta is a clinical diagnosis.

There are no laboratory studies that are specific for a diagnosis of coarctation.

In a critically ill neonate, laboratory studies that may assist with acute management include arterial blood gas measurements, complete blood count, and a chemistry panel.

Would imaging studies be helpful? If so, which ones?

Chest radiograph

Usually low cost, easily obtainable, minimal radiation exposure

May demonstrate mild cardiomegaly, prominent ascending aorta, prominent aortic knob

Classic board question regarding chest radiographic findings

A "3" sign along left mediastinal margin

Rib notching along undersurface of ribs

Echocardiogram

Noninvasive imaging modality, moderate cost, no radiation exposure

Usually diagnostic; however, if suspicion for coarctation is high, a pediatric/congenital cardiology consultation is necessary to interpret study results and guide therapy

Can define any associated intracardiac defects

Evaluates left ventricular function and hypertrophy

Magnetic resonance imaging (Figure 1)

Figure 1.

Cardiac MRI demonstrating discrete coarctation at base of left subclavian artery.

Small children/infants require sedation and/or anesthesia

Inferior when compared with echocardiography due to costs, operator involvement and patient risks

Excellent for defining specifics of anatomy before intervention especially if there are plans for percutaneous catheterization intervention

Angiography (Figure 2 and Figure 3)

Figure 2.

Angiography of discrete coarctation.

Figure 3.

Poststent angioplasty of discrete coarctation.

Angiography would be obtained and performed in conjunction with cardiac catheterization and balloon/stent angioplasty.

Confirming the diagnosis

Neonates presenting in cardiogenic shock with poor perfusion and decreased pulses should have prostaglandin infusion started immediately. This should be accompanied by appropriate resuscitation as dictated by the clinical picture. After initial stabilization, transthoracic echocardiography should be performed to evaluate for the presence of other congenital cardiac defects. If echocardiography is not available, the neonate should be transferred to a congenital cardiac center.

Non-neonatal patients being evaluated for hypertension should have a thorough examination performed. Patients with decreased/absent femoral pulses or discrepancy of blood pressure in the upper and lower extremities should have an echocardiogram performed. Because of the high association with bicuspid aortic valve and coarctation, a finding of an ejection click requires further evaluation to prove that the patient does not have a coarctation.

If you are able to confirm that the patient has a coarctation, what treatment should be initiated?

Coarctation in a neonate

Prostaglandin infusion can be lifesaving in coarctation and other left-sided obstructive cardiac congenital lesions. Begin infusion at 0.1 µg/kg/min. Prostaglandin allows dilation of the ductus arteriosus, which permits blood flow past the coarctation through the ductus arteriosus.

Appropriate resuscitation as warranted based on degree of decompensation (e.g, airway management, fluid bolus, inotropic agents).

Coarctation after the neonatal period

Usually no urgent or emergent therapies/interventions are required.

If a patient presents with poor cardiac output associated with heart failure, treatment should be guided as appropriate by the clinical picture.

Although there may be no urgency, all patients will require surgical or percutaneous intervention for therapy. There is no benefit to delaying therapy and most advocate for timely intervention at the time of diagnosis.

What are the adverse effects associated with each treatment option?

The two treatment options for coarctation are surgical repair with coarctectomy or percutaneous aortic balloon angioplasty or stent angioplasty. Both therapies are acceptable and effective; each has its own risks and benefits. Overall acute mortality for surgical repair, balloon angioplasty, and stent angioplasty is expected to be less than 1%-2%.

The first surgical repair of coarctation was in 1944. Several different techniques have been developed and used: coarctectomy with end-to-end anastomosis, subclavian flap aortoplasty, patch aortoplasty, and placement of an interposition graft. Resection with end-to-end anastomosis is the most commonly used method in most patients with discrete coarcation in the current era.

The highest risk of increased mortality is in patients less than 1 year of age. Current surgical mortality is less than 1%. Overall complications associated with surgery are infrequent. These complications include; recurrent laryngeal nerve injury, bleeding (intraoperative and postoperative), chylothorax resulting from injury to the thoracic duct, mesenteric arteritis (postcoarctectomy syndrome), paradoxical postoperative hypertension, and spinal cord ischemia with transient or permanent neurologic impairment. Higher rates of recurrent coarctation are related to age less than 1 year and technique used.

Percutaneous intervention with balloon angioplasty was first successfully performed in 1982. Initially angioplasty was applied in postoperative recoarctation. However, it has since been used as primary therapy in native coarctation, with varying results. Balloon angioplasty for native coarctation in the neonate has a limited role because of decreased overall efficacy and risk for vascular injuries. In general, the risk for vascular complications has decreased in the past 30 years with improvement in endovascular equipment.

Although balloon angioplasty can be effective, the decreased gradient may not be sustained, with recurrence rates up to 27% and the development of aortic aneurysm as high as 20% in some series. More recently, stent angioplasty for recurrent and native coarctation has been advocated by most interventionalists. This therapy is limited to older children and adults to minimize peripheral vascular complications. Stent angioplasty has the advantage of greater immediate gradient reduction, more sustained results, and fewer aortic vascular events (dissection, aneurysm, or rupture).

What are the possible outcomes of coarctation of the aorta?

Natural history studies all demonstrate that coarctation of the aorta always progresses and worsens over time. Mortality rates for unoperated isolated coarctation range from 45%-84%. The largest series in unoperated coarctation after the first year of life demonstrates a mean age of death of 34 years (compared with 71 years in controls) and a 90% mortality by age 50 years. In this patient population, the most common causes of death were heart failure (25%), aortic dissection (21%), bacterial endocarditis (18%), and intracranial hemorrhage (12%).

Long-term studies have demonstrated persistent late hypertension in as many as 30% of patients. Other studies have demonstrated that this risk is highest when relief of obstruction is performed after 1 year of age with an incidence of only 4% when corrected before 1 year. This low incidence is contrasted to an incidence of 27% in those treated after the age of 1 year. These data underscore the importance of early diagnosis, intervention and long-term follow-up.

What causes this disease and how frequent is it?

Coarctation of the aorta is a common congenital cardiovascular defect caused by abnormal development of the aortic arch. Coarctation is commonly associated with significant complex intracardiac congenital heart defects. Isolated coarctation accounts for approximately 5%-8% of congenital defects.

There is a male predominance with most series composed of nearly two-thirds male patients. Twelve to 17% of patients with Turner syndrome have coarctation of the aorta.

There is no specific genetic event that has been identified as causative for coarctation of the aorta. However, high recurrence rates of left ventricular outflow obstructive lesions (aortic valve stenosis, bicuspid aortic valve, coarctation, hypoplastic left heart syndrome) have been noted in families. The presence of bicuspid aortic valve in first-degree relatives of children with aortic stenosis, coarctation or hypoplastic left heart syndrome has been reported as high as 50% and sibling recurrence rates for these three defects as high as 30%. Linkage analysis of these families have identified three separate areas on chromosomes 2, 10, and 16 that may contribute to increased susceptibility for development of a left ventricular outflow tract obstructive lesion.

How do these pathogens/genes/exposures cause the disease?

Currently the role of these regions is unclear. However, there are areas of overlap that may contribute to an increased susceptibility for the development of a left ventricular outflow tract obstructive lesion (aortic stenosis, bicuspid aortic valve, coarctation, hypoplastic left heart syndrome).

What complications might you expect from the disease or treatment of the disease?

Coarctation of the aorta always progresses and worsens over time. Patients with unrepaired coarctation experience early cardiovascular disease in the form of ventricular dysfunction, cardiomyopathy, bacterial endocarditis, aortic rupture and dissection, or cerebral hemorrhage/stroke associated with berry aneurysms. Late hypertension requiring medical therapy despite adequate relief of obstruction is common in patients who undergo repair after 1 year of age.

How can coarctation be prevented?

Coarctation of the aorta is a congenital defect.

What is the evidence?

Tanous, D, Benson, LN, Horlick, EM. "Coarctation of the aorta: evaluation and management". Curr Opin Cardiol. vol. 24. 2009. pp. 509-15.

(Good general review of coarctation, including therapies, risks associated with therapy, and long-term outcomes.)

Shaddy, RE, Boucek, MM, Sturtevant, JE. "Comparison of angioplasty and surgery for unoperated coarctation of the aorta". Circulation. vol. 87. 1993. pp. 793-99.

(Small study evaluating the acute and early results in patients prospectively randomized to either balloon aortic angioplasty or surgical repair.)

Cowley, CG, Orsmond, GS, Feola, P. "Long-term, randomized comparison of balloon angioplasty and surgery for native coarctation of the aorta in childhood". Circulation. vol. 111. 2005. pp. 3453-56.

(Follow-up on previously randomized patients [see Shaddy et al above] for long-term outcomes.)

Holzer, RJ, Qureshi, S, Ghasemi, A. "Stenting of aortic coarctation: acute, intermediate, and long-term results of a prospective multi-institutional registry—Congenital Cardiovascular Interventional Study Consortium (CCISC)". Catheter Cardiovasc Interv. vol. 76. 2010. pp. 553-63.

(Review of large multi-institutional congenital interventional database of patients who underwent stent angioplasty for coarctation. Good discussion of immediate outcomes as well as risks and complications associated with stent angioplasty. Some limited intermediate and long-term data are available and are comparable to previously published data.)

Egan, M, Holzer, RJ. "Comparing balloon angioplasty, stenting and surgery in the treatment of aortic coarctation". Expert Rev Cardiovasc Ther. vol. 7. 2009. pp. 1401-12.

(A good discussion/review of the three treatment strategies and the problems inherent in direct comparisons.)

Seirafi, PA, Warner, KG, Geggel, RL. "Repair of coarctation of the aorta during infancy minimizes the risk of late hypertension". Ann Thorac Surg. vol. 66. 1998. pp. 1378-82.

(A large retrospective analysis of the long-term risk of late hypertension related to timing of repair.)

Campbell, M. "Natural history of coarctation of the aorta". Br Heart J. vol. 32. 1970. pp. 633-40.

(Largest and most comprehensive review of the natural history of coarctation.)

McBride, KL, Zender, GA, Fitzgerald-Butt, SM. "Linkage analysis of left ventricular outflow tract malformations (aortic valve stenosis, coarctation of the aorta, and hypoplastic left heart syndrome)". Eur J Hum Genet. vol. 17. 2009. pp. 811-19.

(A genetic analysis of family members of patients with left ventricular outflow obstructive lesions that demonstrates common linkage for these lesions.)

Ongoing controversies regarding etiology, diagnosis, treatment

There is little debate that surgical repair with resection in the neonate is considered the preferred treatment method at most institutions. However, there does exist some controversy regarding the actual surgical approach in this patient population. In the case of a discrete shelf-like stenosis, a lateral thoracotomy with coarctectomy and end-to-end anastomosis is adequate. However, if there is any degree of proximal arch hypoplasia, a mediastinal approach with a more extended arch reconstruction is required. If arch hypoplasia is underestimated or not recognized, and thoracotomy with resection only is performed, there is a higher risk of recoarctation.

As alluded to in the previous discussion on treatment modalities, there is some controversy regarding preferred intervention of angioplasty, stent angioplasty, and surgery. Direct comparison of the three options is difficult given the different "generation" of surgical outcomes data compared with current percutaneous interventions. Additionally, there are limited data from randomized controlled trials.

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