Disclosure
Background: Coarctation of aorta is a common congenital cardiovascular defect characterized by upper-body hypertension due to varying degrees of constrictions of the aorta. These constrictions may occur at any point from the transverse arch to the iliac bifurcation. Pathophysiology: Coarctation of the aorta can occur as a discrete juxtaductal obstruction or as tubular hypoplasia of the transverse aorta starting at one of the head or neck vessels and extending to the ductal area (preductal or infantile-type coarctation. Often, both components are present. Aortic coarctation is most likely related to an abnormality in the pattern of ductus arteriosus blood flow in utero, which, in turn, may be the result of associated intracardiac anomalies. In fetal life, blood flow through the aortic isthmus constitutes only 12-17% of the total cardiac output, whereas blood flow through the ductus arteriosus exceeds that across the aortic valve. Coarctation is initiated by the presence of a cardiac abnormality that results in decreased blood flow anterograde through the aortic valve (eg, bicuspid aortic valve, ventricular septal defect [VSD]). In the first few days of life, the patent ductus arteriosus may serve to widen the juxtaductal area of the aorta and provide temporary relief from the obstruction. In these acyanotic infants, net left-to-right ductal shunting occurs. In contrast, with more severe juxtaductal coarctation or i transverse arch hypoplasia, right ventricular blood is ejected through the ductus to supply the descending aorta, as it does during fetal life. Perfusion of the lower body then depends on right ventricular output. In this situation, the femoral pulses are palpable, and differential blood pressures may not be helpful in making the diagnosis. The ductal right-to-left shunting is manifested as differential cyanosis, with the upper extremities being pink and the lower extremities being blue. Such infants may have severe pulmonary hypertension and high pulmonary vascular resistance. Signs of heart failure are prominent. Occasionally, severely hypoplastic segments of the aortic isthmus may become completely atretic, resulting in an interrupted aortic arch, with the left subclavian artery arising either proximal or distal to the interruption. Coarctation associated with arch hypoplasia was referred to as infantile type because it usually presented in early infancy due to its severity. Adult type referred to the isolated juxtaductal coarctation, which, if mild, usually does not present until later childhood. Blood pressure is elevated in the vessels that arise proximal to the coarctation; blood pressure and pulse pressure below the constriction are lower. Hypertension is not due to the mechanical obstruction alone but also involves neurohumoral mechanisms. Unless operated on in infancy, patients with coarctation of the aorta usually develop an extensive collateral circulation, chiefly from the branches of the subclavian, the superior intercostal, and the internal mammary arteries to create channels for arterial blood to bypass the area of coarctation. The vessels contributing to the collateral circulation may become markedly enlarged and tortuous by early adulthood. After pharmacologic interventions that dilate the ductus arteriosus (prostaglandin E1 infusion) are administered, the pressure difference may be obliterated across the site of coarctation because the fetal flow pattern is reestablished. The pathogenesis of juxtaductal coarctation already described explains the prevalence of associated intracardiac anomalies that foster reduced ascending aortic flow and augmented ductus arteriosus flow in utero, as well as the absence of associated intracardiac anomalies in which the converse flow conditions exist in utero. The dependence of aortic obstruction on constriction of the ductus arteriosus postnatally explains the variable onset after birth of the clinical manifestations of coarctation, as well as the dramatic alleviation of the obstruction produced pharmacologically by dilatation of the ductus arteriosus. Frequency:
Mortality/Morbidity: Abnormalities of the aortic valve are present in most patients. Bicuspid aortic valves are common but usually do not produce clinical signs unless the stenosis is significant. The association of a patent ductus arteriosus (PDA) with coarctation of the aorta is also common. VSDs and atrial septal defects (ASDs) may be suspected when signs of a left-to-right shunt are present. These are worsened by the increased resistance to flow through the left side of the heart. Mitral-valve abnormalities are also occasionally seen, as is subvalvular aortic stenosis. In rare cases, severe neurologic damage or even death may occur from associated cerebrovascular disease. Subarachnoid or intracerebral hemorrhage may result from rupture of congenital aneurysms in the circle of Willis, of other vessels with defective elastic and medial tissue, or of normal vessels; these accidents are secondary to hypertension. Abnormalities of the subclavian arteries may include involvement of the left subclavian artery in the area of coarctation, stenosis of the orifice of the left subclavian artery, and anomalous origin of the right subclavian artery. Untreated, the great majority of older patients with coarctation of the aorta succumb to the disease at age 20-40 years. Some live well into mid life without serious disability. The common serious complications are related to systemic hypertension, which may result in premature coronary artery disease, heart failure, hypertensive encephalopathy, or intracranial hemorrhage. Heart failure may be worsened by associated anomalies. Infective endocarditis or endarteritis is a significant complication in adults. Aneurysms of the descending aorta or of the enlarged collateral vessels may develop. In infants with severe coarctation, heart failure and hypoperfusion may be life threatening and require immediate medical intervention. Race: No particular racial predilection is described. Sex: This left-sided obstructive lesion occurs most frequently in males, with a male-to-female ratio approaching 3:1. Age:
Anatomy: Coarctation of the aorta is a narrowing usually in the region of the ligamentum arteriosum. It may be discrete or associated with hypoplasia of the aortic arch and isthmus. The specific anatomy, severity, and degree of hypoplasia proximal to the coarctation are highly variable. Complex coarctation is used to describe coarctation in the presence of other important intracardiac anomalies (eg, VSD, left ventricular outflow tract obstruction [LVOTO], and mitral stenosis) and is usually detected in infancy. Simple coarctation refers to coarctation in the absence of such lesions. It is the most common form detected de novo in adults. Associated abnormalities include bicuspid aortic valve in 50-85% of cases, intracranial aneurysms (most commonly of the circle of Willis), and acquired intercostal artery aneurysms. One definition of significant coarctation is one with a gradient of greater than 20 mm Hg across the coarctation site at angiography with or without proximal systemic hypertension. A second definition of significant coarctation requires the presence of proximal hypertension in the company of echocardiographic or angiographic evidence of aortic coarctation. Of note, if extensive collateral circulation is present, the patient may have minimal or no pressure gradient and acquired aortic atresia. The conventional anatomic and clinical divisions into preductal (infantile) and postductal (adult) coarctation are misleading because the anatomical localization is inaccurate and the age-dependency of the clinical presentation does not always hold true (ie, the adult type often is seen in the first weeks of life). A spectrum of anatomic lesions exists, causing obstruction of the aortic arch or proximal portion of the descending aorta. These range from a localized coarctation or constriction of the lumen, most commonly located just distal to the origin of the left subclavian artery and closely related to the attachment of the ductus arteriosus with the aorta, to diffuse narrowing or interruption of a portion of the aortic arch. In this article, aortic arch obstruction is divided into 3 types: (1) localized juxtaductal coarctation, (2) hypoplasia of the aortic isthmus, and (3) aortic arch interruption. Pseudocoarctation is used synonymously with kinking or buckling of the aorta, which is a subclinical form of localized juxtaductal coarctation of the aorta. Pathologic anatomy About 98% of coarctations occur immediately beneath the origin of the left subclavian artery at the site of attachment of the ductus arteriosus (juxtaductal coarctation). Coarctation of the aorta may be a feature of Turner syndrome. Aortic coarctation is associated with a bicuspid aortic valve in more than 70% of patients. Mitral valve abnormalities, such as a supravalvular mitral ring or parachute mitral valve, and subaortic stenosis are potential associated lesions. When these left-sided obstructive lesions occur together, they are referred to as the Shone complex. Coarctation often occurs in infancy associated with other major cardiovascular anomalies, including hypoplastic left heart, severe mitral or aortic valve disease, transposition of the great arteries, and variations of double-outlet or single ventricle. Severe coarctation may also be associated with endocardial fibroelastosis. The clinical manifestations depend on the effects of the associated malformations and on the coarctation itself. Clinical Details: The clinical findings are highly variable and range from left ventricular failure in infancy to systemic hypertension in otherwise asymptomatic adult patients, depending on the site and severity of the coarctation and the presence of associated abnormalities. The classic sign of coarctation of the aorta is a disparity in pulsations and blood pressures of the arms and legs. The femoral, popliteal, posterior tibial, and dorsalis pedis pulses are weak (or absent in up to 40% of patients), in contrast to the bounding pulses of the arms and carotid vessels. The radial and femoral pulses should always be palpated simultaneously for the presence of a radial-femoral delay. Normally, the femoral pulse occurs slightly before the radial pulse. A radial-femoral delay occurs when blood flow to the descending aorta is dependent on collaterals, in which case the femoral pulse is felt after the radial pulse. In healthy persons, the systolic blood pressure in the legs obtained by the cuff method is 10-20 mm Hg higher than that in the arms. In coarctation of the aorta, the blood pressure in the legs is lower than that in the arms; frequently, it is difficult to obtain. This differential in blood pressures is common in patients with coarctation who are older than 1 year of age, about 90% of whom have systolic hypertension in an upper extremity greater than the 95th percentile for age. It is important to determine the blood pressure in each arm; a pressure higher in the right than the left arm suggests involvement of the left subclavian artery in the area of coarctation. Occasionally, the right subclavian may arise anomalously from below the area of coarctation, resulting in a left arm pressure that is higher than the right. With exercise, there is a more prominent rise of systemic blood pressure and the upper-to-lower extremity pressure gradient increases. The precordial impulse and heart sounds are usually normal; the presence of a systolic ejection click or thrill in the suprasternal notch suggests the presence of a bicuspid aortic valve (present in 70% of cases). A short systolic murmur is often heard along the left sternal border at the third and fourth intercostal spaces. The murmur is well transmitted to the left infrascapular area and occasionally to the neck. Often, the typical murmur of mild aortic stenosis can be heard in the third right intercostal space. Occasionally, more significant degrees of obstruction across the aortic valve are present. The presence of a low-pitched mid-diastolic murmur at the apex suggests the presence of mitral valve stenosis. Among older patients with well-developed collateral blood flow, systolic or continuous murmurs may be heard over the left and right sides of the chest laterally and posteriorly. In these patients, a palpable thrill can occasionally be appreciated in the intercostal spaces on the back. Age-related considerations Coarctation of the aorta recognized after infancy is rarely associated with significant symptoms. Some children or adolescents complain about weakness or pain (or both) in the legs after exercise, but in many instances, even patients with severe coarctation are asymptomatic. Older children are frequently brought to the cardiologist's attention when they are found to be hypertensive on routine physical examination. Neonates or infants with more severe coarctation, usually including some degree of transverse arch hypoplasia, present with signs of lower-body hypoperfusion, acidosis, and severe heart failure. This presentation may be delayed days or weeks until after closure of the ductus arteriosus. If identified before ductal closure, patients may exhibit differential cyanosis, which is best demonstrated by simultaneous oximetry of the upper and lower extremities. On physical examination, the heart is large, and a systolic murmur is heard along the left sternal border with a loud second heart sound. Associated anomalies The most common associated anomaly is a bicuspid aortic valve, which occurs in as many as 85% of patients with coarctation of the aorta. Other associated anomalies include the following: VSD, stenosis or atresia of the left subclavian artery, PDA, Turner syndrome PDA, and mitral valve prolapse. Preferred Examination: The diagnosis can be made by a careful evaluation of the pulses in all major accessible peripheral arteries and by comparative blood pressure determinations in the arms and legs. Electrocardiography The electrocardiogram is usually normal in young children but reveals evidence of left ventricular hypertrophy in older patients. Neonates and young infants display right or biventricular hypertrophy. Radiography The findings on radiographic examination depend on the age of the patient and on the effects of hypertension and collateral circulation. Infants with severe coarctation have cardiac enlargement and pulmonary congestion. During childhood, the findings are not striking until after the first decade, when the heart tends to be mildly or moderately enlarged because of left ventricular prominence. The enlarged left subclavian artery commonly produces a prominent shadow in the left superior mediastinum. Notching of the inferior border of the ribs from pressure erosion by enlarged collateral vessels is common by late childhood. In most instances, an area of poststenotic dilatation of the descending aorta is present. Echocardiography The segment of coarctation can usually be visualized by 2-dimensional echocardiography; associated anomalies of the mitral and aortic valve can also be demonstrated. The descending aorta is hypopulsatile. Color Doppler imaging is useful for demonstrating the specific site of the obstruction. Pulsed and continuous-wave Doppler study can be used to determine the pressure gradient directly at the area of coarctation. However, in the presence of a patent ductus arteriosus, the severity of the narrowing may be underestimated. Cardiac catheterization Cardiac catheterization with selective left ventriculography and aortography is useful in evaluating selected patients with additional anomalies and as a means of visualizing collateral blood flow. In cases that are well defined by echocardiography, diagnostic catheterization is usually not required prior to surgery. Limitations of Techniques: Radiographs have limitations. CT or MRI may be helpful.
Aorta, Dissection
Turner syndrome
Findings: The diagnosis of coarctation of the aorta can be established from the posteroanterior (PA) chest image alone in up to 92% of patients. Widening of the left subclavian artery border is the most common finding, but the most useful radiographic sign is an abnormal contour of the aortic arch, which may appear as a double bulge above and below the usual site of the aortic knob. This pattern has been described as a figure-3 sign. The upper arc of the 3 is the dilated arch proximal to the coarctation and/or a dilated left subclavian artery. The lower arc or bulge represents poststenotic dilatation of the aorta immediately below the coarctation. The indentation between the 2 bulges is the coarctation itself. When the esophagus is filled with barium, a reverse 3 or E sign is often seen and represents a mirror image of the areas of prestenotic and poststenotic dilatation. The 3 sign is variable in that the upper arc may be small and the lower arc large or vice versa. Superior mediastinal widening or sternal scalloping caused by large internal mammary collateral arteries is visible in some patients. A prominent left ventricular border often occurs with coarctation, particularly when a bicuspid aortic valve is associated with aortic stenosis. Bilateral symmetrical rib notching, readily appreciated on the chest image, is diagnostic of aortic coarctation. It is due to obstructed blood flow at the narrowed aortic segment with collateral blood flow through the intercostal arteries. Rib notching is unusual in infancy, but becomes more frequent with increased age and is present in 75% of adults with coarctation. Rib notching occurs along the inferior margin of the third to the eighth ribs and is caused by pulsation of dilated intercostal arteries. The major pathways of collateral flow include the following: (1) subclavian artery to the internal mammary artery to the intercostal arteries, (2) subclavian artery to the costovertebral trunk to the intercostal arteries, and (3) transverse cervical and suprascapular arteries to the intercostal arteries. The findings on radiographic examination depend on the age of the patient and on the effects of hypertension and collateral circulation. In infants with severe coarctation, cardiac enlargement and pulmonary congestion are present. During childhood, the findings are not striking until after the first decade, when the heart tends to be mildly or moderately enlarged because of left ventricular prominence. The enlarged left subclavian artery commonly produces a prominent shadow in the left superior mediastinum. Notching of the inferior border of the ribs from pressure erosion by enlarged collateral vessels is common by late childhood. In most instances, an area of poststenotic dilatation of the descending aorta is present. Degree of Confidence: The diagnosis of coarctation of the aorta can be established from the PA chest image alone in up to 92% of patients. |
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Findings: CT scanning does not play a significant role in the evaluation of aortic coarctation.
Findings: MRI vividly portrays the anatomy of the coarctation and also demonstrates the bicuspid valve and the state of left ventricular function, as well as restenosis following angioplasty or surgical repair. Degree of Confidence: The degree of confidence is very high.
Findings: The segment of coarctation can usually be visualized by means of 2-dimensional echocardiography. Associated anomalies of the mitral and aortic valve can also be demonstrated. The descending aorta is hypopulsatile. Color Doppler imaging is useful for demonstrating the specific site of the obstruction. Pulsed and continuous wave Doppler study can be used to determine the pressure gradient directly at the area of coarctation. Degree of Confidence: In the presence of a patent ductus arteriosus, the severity of the narrowing may be underestimated.
Findings: Cardiac catheterization with selective left ventriculography and aortography is useful in selected patients with additional anomalies and in visualizing collateral blood flow. In cases that are well defined by echocardiography, diagnostic catheterization is usually not required prior to surgery.
Intervention: In neonates with severe coarctation of the aorta, closure of the ductus often results in hypoperfusion, acidosis, and rapid deterioration. These patients should be given an infusion of prostaglandin E1 to reopen the ductus and reestablish adequate lower extremity blood flow. Once a diagnosis has been confirmed and the patient stabilized, surgical repair should be performed. Older infants who present with heart failure but with good perfusion should be managed with anticongestive measures to improve their clinical status prior to surgical intervention. Older children with significant coarctation of the aorta should be treated relatively soon after diagnosis. Delay is unwarranted, especially after the second decade of life, when the operation may be less successful because of decreased left ventricular function and degenerative changes in the aortic wall. Nevertheless, if cardiac reserve is sufficient, satisfactory repair is possible well into midadult life. Associated valvular lesions increase the hazards of late surgery. The procedure of choice for isolated juxtaductal coarctation of the aorta is controversial. This operation remains the procedure of choice, and several surgical techniques are used. The area of coarctation can be excised, and a primary reanastomosis performed. Often, the transverse aorta is splayed open and an extended end-to-end anastomosis is performed to increase the effective cross-sectional area of the repair. The subclavian flap procedure, which involves division of the left subclavian artery and its incorporation into the wall of the repaired coarctation, is used by some, often in the younger age group. Others favor a patch aortoplasty, in which the area of coarctation is enlarged with a roof of prosthetic material. After operation, a striking increase in the amplitude of pulsations occurs in the lower extremities. In the immediate postoperative course, rebound hypertension is common and requires medical management. This exaggerated hypertension gradually subsides, and, in most patients, antihypertensive medications can be discontinued. Residual murmurs are common and may be due to associated cardiac anomalies, to a residual flow disturbance across the repaired area, or to collateral blood flow. Rare additional operative problems include spinal cord injury due to aortic cross-clamping if poorly developed collaterals, chylothorax, diaphragm injury, or laryngeal nerve injury occurs. If a left subclavian flap is used, the radial pulse and blood pressure in the left arm are diminished or absent. In some centers, balloon angioplasty has been used for the treatment of a native or unoperated-on coarctation. Early reports of results in these patients indicate good relief of the obstruction. However, several have reported the subsequent development of aortic aneurysms. Revised techniques have reduced the incidence of this complication, although the use of angioplasty in native coarctation remains controversial. Substantial controversy exists regarding the role of balloon angioplasty with or without the use of stents, in the treatment of native coarctation, especially among younger patients. After angioplasty, remain strongly concerned about the presence of residual pressure gradients, aneurysm formation, aortic dissection and rupture, and femoral arterial complications. Although angioplasty can effectively reduce obstruction in many patients, the late outcome is often unpredictable. Repair of coarctation in the second decade of life or beyond may be associated with a higher incidence of premature cardiovascular disease, even in the absence of residual cardiac abnormalities. There may be early onset of adult hypertension, which has occurred even in patients with adequately resected coarctation. Although restenosis in older patients after coarctectomy is rare, a significant number of infants operated on before 1 year of age require revision later in childhood. All patients should be followed carefully for the development of re-coarctation and aortic aneurysm. Should re-coarctation occur, balloon angioplasty is the procedure of choice. In these patients, scar tissue from prior surgery makes repeat operation more difficult, yet makes balloon angioplasty safer because of the lower incidence of aneurysm formation. Relief of obstruction with this technique is usually excellent. Intravascular stents have been used in some patients. Coarctation of the aorta associated with severe mitral and aortic valve disease may have to be treated within the context of the hypoplastic left heart syndrome even if the left ventricular chamber is not severely hypoplastic. Such patients usually have a long segment of narrow transverse aortic arch with or without an isolated coarctation at the site of the ductus arteriosus. Coarctation of the aorta with transposition of the great arteries or single ventricle may be repaired alone or in combination with other palliative measures. Medical/Legal Pitfalls:
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