Aortic coarctation overview

# Overview
Aortic coarctation is a localized narrowing or abrupt constriction of the aortic arch anywhere along its length. It is most common distal to the origin of the left subclavian artery, near the area where the ductus arteriosus (ligamentum arteriosum after its regression) inserts. Less commonly, the obstruction can occur in the abdominal aorta.  Coarctation may be associated with a bicuspid aortic valve.
There is a dilation of the aorta immediately above the narrowing, but especially just below. Therefore the latin term coarctatus, which means contracted or tightened.

# Historical Perspective
Aortic coarctation has been on historical record since as early as 1760. In the 1900s, researchers such as Bonnett and Johnson would later further classify the anatomical configurations associated with aortic coarctation.

# Classification
An aortic coarctation can be classified in three ways depending on the anatomical configuration. These include: preductal coarctation, ductal coarctation, and postductal coarctation. All classifications involve narrowings of the aorta that directly impact the aortic hemodynamics.

# Pathophysiology
An aortic coarctation results from both, congenital and acquired means. Factors directly influencing the pathophysiology include defect location and sites of secondary dilation.

# Causes
Like many congenital heart diseases, the cause of aortic coarctation is not clear. The etiology of coarctation of the aorta may be explained by multifactorial inheritance hypothesis. Clinical studies suggest that genetic, familial influence and environmental factors both play an important role during pregnancy. It has been found to be associated more with patients with Turner syndrome. Additional research suggests a possible link between other congenital heart diseases and an aortic coarctation, indicating that those with congenital heart disease are more likely to have an accompanying secondary defect.

# Differentiating Aortic Coarctation from other Diseases
A thorough examination is necessary to truly diagnose an aortic coarctation. Conditions with similar symptoms to an aortic coarctation include: aortic stenosis, cardiomyopathies (dilated cardiomyopathy and hypertrophic cardiomyopathy), endocardial fibroelastosis, primary hypertension, hypoplastic left heart syndrome, viral myocarditis, congenital adrenal hyperplasia, patent ductus arteriosus, polyarteritis, sepsis, and shock from a variety of causes.

# Epidemiology and Demographics
Coarctation of the aorta is a common malformation. It occurs in about 7% of patients with congenital heart defects.  It is more common in males than females with a ratio of 2:1. Up to 25% of patients with Turner syndrome have coarctation of the aorta. It is more common in caucasians with approximately 7 times more cases in caucasians versus asian.

# Risk Factors
Although the cause of aortic coarctation is not definitively known, certain factors have been associated with a potential risk increase. These include genetic anomalies such as Turner Syndrome, familial history, environmental factors (viral infections during pregnancy), and neonatal care.

# Screening
Arterial hypertension in the right arm with normal to low blood pressure in the lower extremities should prompt consideration of the diagnosis of aortic coarctation.

# Natural History, Complications and Prognosis
An aortic coarctation is generally symptomatic enough during childhood to prompt evaluation, and approximately 80% of cases are diagnosed during childhood.  The remaining 20% of cases are often less symptomatic with less severe narrowing, but will ultimately require correction or irreversible organ damage can occur. Common complications, when left untreated, include: aortic rupture, infective endocarditis, congestive heart failure, and calcification of the aorta.

# Diagnosis

## History and Symptoms
Common symptoms include dizziness, fainting (or frank syncope), shortness of breath (dyspnea), severe headache most likely due to hypertension, chest pain (angina), cold feet/legs, nosebleed, leg cramps with exercise, high blood pressure (hypertension) with exercise, decreased ability to exercise, and poor growth.

## Physical Examination
Physical examination acts as an important tool in the diagnosis of coarctation of aorta. Differential hypertension (depending on the location of coarctation) is often present with increased blood pressure in the upper extremities and relative hypotension in the lower extremities. The difference is usually in systolic blood pressure whereas the diastolic blood pressures are typically similar.  Similarly, the pulses in upper extremities are bounding whereas the femoral pulses are often diminished (brachial-femoral delay]). There are 3 potential sources of a murmur: multiple arterial collaterals (continuous murmur), an associated bicuspid aortic valve (systolic ejection click), and the coarctation itself which can be heard over the left infraclavicular area and under scapula. Murmurs due to associated cardiac abnormalities such as VSD or aortic valve stenosis, may also be detected. Neonates may present with discrepancies in blood pressure and pulses between the limbs, differential cyanosis or reversed differential cyanosis (depending on associated lesions), murmur, congestive heart failure, and shock. Older children and adolescent may be referred due to agitated behavior, headache, vision problems, and hypertension.

## Electrocardiogram
Electrocardiogram may be used as a diagnostic tool in the evaluation of an aortic coarctations. ECG findings associated with an aortic coarctation depend on the severity of the coarctation. Milder cases may show signs of a normal ECG. However, more severe coarctations will have abnormal ECGs showing evidence of left ventricular hypertrophy.

## Chest X Ray
Aortic coarctation on chest X ray presents with irregular notching of the inferior margins of the posterior ribs resulting from collateral flow through dilated and pulsatile intercostal arteries. An inverted "3" sign of the barium-filled esophagus or a "3" sign on a highly penetrated chest radiograph may be visualized. There are often signs of congestive heart failure including cardiomegaly, pulmonary edema, and prominent pulmonary vasculature on the chest X ray.

## MRI
Magnetic resonance imaging (MRI) can define the location and severity of a coarctation. MRI can also detect associated cardiac abnormalities and is  used for serial follow-up after surgical repair or balloon angioplasty. MRI  is recommended to look for aneurysm formation following repair of a coarctation.  MR angiography has almost completely replaced invasive catheter based techniques for evaluating re coarctation. In adults with untreated coarctation blood often reaches the lower body through collaterals, eg. internal thoracic arteries via the subclavian arteries. These can be visualized on MR or angiography.

## CT
CT is useful in older or postoperative patients as it helps in to assessing residual obstruction, hypoplasia, aneurysms, multiple surgical clips or a stent present in the area of coarctation. 

## Echocardiography
Echocardiography is an useful diagnostic tool for coarctation of aorta. The 2 D echocardiography helps in the evaluation of the aortic arch to assess the transverse aortic arch, isthmus, severity of coarctation, and other associated cardiac abnormalities.  Doppler echocardiography determines the gradient across the coarctation and guides decisions regarding treatment.

# Treatment

## Medical Therapy
The treatment choice depends on the patients age of presentation, severity, the location of the coarctation and other associated anomalies. For children who present early, the role of medical management lies in stablizing the patient for surgery. However, in older kids and adolescent presenting with hypertension treatment is guided towards correction of hypertension and other associated anomalies. Beta blocker is treatment of choice for both pre and post operative hypertension.

## Surgery
Therapy/Treatment is conservative if asymptomatic, but may require surgical resection of the narrow segment if there is arterial hypertension. The first operations to treat coarctation were carried out by Clarence Crafoord in Sweden in 1944. In some cases angioplasty can be performed to dilate the narrowed artery. If the coarctation is left untreated, arterial hypertension may become permanent due to irreversible changes in some organs (such as the kidney).

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