Coarctation of the aorta

What is Coarctation of the Aorta?

Coarctation of the aorta is a congenital heart defect characterized by the presence of segmental aortic narrowing of any localization.

Embryology

In the embryo the aortic isthmus normally is narrowed, as no more than 1/3 of the whole blood flow passes into the descending aorta, and 2/3 get there through the PDA from the pulmonary artery. Development of the aortic isthmus depends even more on the function of the arterial duct, in case of concomitant heart defects that create an imbalance between the outflow tracts of the right and left ventricles. Increased ductal function leads to pathological narrowing of the isthmus.

Coarctation of the aorta may be the result of the fetal abnormal blood circulation in cases where is an obstacle to the ejection of blood into the ascending aorta. In the presence of a stenosing bicuspid aortic valve, blood flow from right to left through the PDA increases during prenatal development, which contributes to the migration of ductal tissues into the adjacent aortic wall. Ductal tissues along with smooth muscle cells spread throughout the aortic perimeter. Ductal tissue contracts and fibroses, leading to a narrowing of this aortic segment. 

Anatomy

Morphologically, an accumulation of smooth muscle cells and myxomatous tissue in the coarctation area is found. There is a theory that these cells migrate into the aorta from the ductus arteriosus. The most common location of coarctation is the descending aorta after the left subclavian artery ostium. In rare cases, segmental narrowing of the aorta can be in any part of it. There are 3 anatomical types of coarctation of the aorta: preductal (child type), postductal (adult type), and juxtaductal. Juxtaductal type (neonatal) - ductus arteriosus opens in the coarctation area. The closure of PDA leads to the rapid development of heart failure, as the coarctation area simultaneously narrows. In addition to narrowing of the aorta in isolated coarctation, hypertrophy and impaired contractility of the left ventricle can be found. 

Frequent concomitant anomalies are: aortic arch hypoplasia, bicuspid aortic valve, HLHS, single ventricle with obstruction of systemic blood flow, etc.

Classification

1. Preductal;
2. Ductal;
3. Postductal.

Hemodynamics

In the presence of critical neonatal coarctation during the prenatal period, blood supply to the lower body occurs through the ductus arteriosus, which is maintained by high pulmonary resistance. When the duct is closed after birth, heart failure develops rapidly. Clinically manifested by the absence of pulsation in the femoral arteries, the child becomes lethargic. At the same time, pulmonary blood flow increases, which leads to the development of pulmonary edema. 

Over time, acidosis progresses, multiple organ failure develops, which ultimately leads to death. With a slow closure of the preductal coarctation, hemodynamic disturbances consist in a decrease in the perfusion of the lower body; as a rule, there is no sharp development of severe organ disturbances. In the adult type of coarctation of the aorta, collateral vessels form, through which blood supply to the descending aorta occurs. With this type of defect, the diagnosis is often not made in time; clinically, one can observe the difference in pressure on the arms and legs and a slight lag in physical development.

Diagnostics

• Echocardiography, CT. Visualization of the defect.
• ECG. Signs of an overload of the right heart predominate in the first months of life. From 6-12 months, signs of an overload of the left parts of heart prevail.
• Chest X-ray. Mild venous congestion in the lungs, an increased heart shadow.
• Cardiac catheterization with aortography. Used to clarify the accompanying CHD or there is a suspicion of an aortic arch interruption.

Clinical presentation

The clinical presentation depends on the patient's age, the presence of concomitant heart abnormalities and the anatomical features of the defect. The majority of newborns with this heart defect have insufficient weight and length of the body, and a disproportionately large head. Obvious pulsation of the carotid and subclavian arteries can be detected upon examination. The skin color of the upper and lower extremities may be different: the so-called differential cyanosis. It is characteristic for the preductal coarctation, because the blood supply to the lower part of the body is carried out by venous blood from the arterial duct. Pulsation of collateral vessels is detected on the upper parts of the chest. The pulsation of the abdominal aorta and femoral arteries is significantly weakened or absent. There is a pressure gradient between the upper and lower limbs. 

Blood pressure is increased on the upper limbs. Intense systolic murmur is heard in the ІІ – ІІІ intercostal space on the left sternal border. It extends to the vessels of the neck and in interscapular space, more on the left side. This murmur is created by a blood stream passing through the narrowing part and collateral vessels, and vibrations of the aortic wall. Particular attention should be paid to the function of the PDA among newborns with preductal coarctation, as the closure of the duct leads to acute hypoperfusion of the lower half of the body, the development of heart failure, impaired renal function.

Treatment

Conservative therapy is aimed at reducing the metabolic needs of the body, treating heart failure, symptomatic therapy.

The lack of effect of conservative therapy, a high probability of severe complications of an uncorrected defect, good immediate and long-term results of elimination of coarctation of the aorta made the surgical method of treatment generally accepted. Most authors agree on the “surgical age” of patients, preferring early intervention.

More often, several fundamentally different types of surgery are used, namely: narrowing resection with end-to-end anastomosis, extended anastomosis in the presence of concomitant hypoplasia of the aortic arch, options for plasty using the subclavian artery and, in rare cases, expansion with a patch or prosthetics. To reduce the risk of aortic recoarctation, it is necessary to completely resect the narrowed area, because the myxomatous tissue located in it will lead to the development of coarctation in the long-term period.



Endovascular correction methods are also used: balloon dilation and stenting. Endovascular balloon dilation is more commonly used for re-coarctation. Its primary use is limited due to the high frequency of recoarctations. Stenting of the coarctation zone is also rarely used.

In the presence of concomitant heart anomalies, attacks of cardiac decompensation often occur in the systemic circulation (peripheral edema, hepatomegaly) or in the small circle (pulmonary edema, cyanosis). In such cases, the correction must be performed according to vital indications.