Aort Koarktasyonu

The aorta is the main artery that arises from the left ventricle and distributes oxygenated blood to the whole body. A congenital narrowing of the aorta distal to the aortic valve is called coarctation of the aorta. The narrowing is usually located beyond the origin of the arteries supplying the head and the arms, in the segment where the aorta turns downward, close to the insertion site of the ductus arteriosus — the region known as the ligamentum arteriosum.

When the aorta narrows beyond the valve, the afterload of the left ventricle increases, exactly as it does in aortic valve stenosis, and the left ventricle responds by working harder and increasing its muscle mass. If the narrowing goes unrecognised and the pressure overload persists, however, left ventricular failure may develop.

The principal mechanism responsible for the signs and symptoms of aortic coarctation is a marked rise in blood pressure in the segment between the narrowing and the ventricle — that is, upper-extremity hypertension affecting the arteries that supply the brain and the arms. Distal to the narrowing, blood pressure is reduced, particularly in the arteries supplying the legs. Because of this, growth and strength are normal in the arms, whereas growth retardation and weakness may be seen in the legs.

The narrowing may be completely asymptomatic and may come to light incidentally, when a murmur is heard over the back during examination or when elevated blood pressure is detected. In a healthy person the blood pressure measured in the leg arteries is higher than the blood pressure measured in the arms; in a patient with aortic coarctation the reverse is found — the blood pressure measured in the arms is higher than that measured in the legs. Frequent nosebleeds (epistaxis) and headaches may occur as a consequence of the elevated blood pressure.

Three types of the disease are described: preductal, ductal and postductal.

• Preductal type: the narrowing lies in the region of the ligamentum arteriosum, the remnant of the ductus arteriosus — the connection between the left pulmonary artery and the aorta.
• Ductal type: the narrowing lies exactly at the insertion site of the ductus arteriosus.
• Postductal type: the narrowing lies distal to the ductus.

Other cardiac abnormalities may coexist with aortic coarctation, such as a bicuspid aortic valve, valvular or subvalvular aortic stenosis, ventricular septal defect (VSD), patent ductus arteriosus (PDA) and congenital anomalies of the mitral valve. An adult patient with aortic coarctation may also have cerebral artery aneurysms, ocular disorders, haemangiomas, hypospadias — a condition in which the urethra opens on the undersurface of the penis, in a more proximal position than normal — or polycystic kidney disease.

How is the diagnosis made?

The condition is usually suspected when a murmur is detected over the back on physical examination, or when a difference in blood pressure between the arms and the legs is found. In adulthood the diagnosis can today be established without difficulty using echocardiography, a highly advanced ultrasound technique. The best method both for establishing the diagnosis and for localising the coarctation, however, is aortic angiography (aortography), performed in the angiography laboratory by injecting contrast medium into the aorta. Although computed tomography and magnetic resonance imaging also give very good results, aortography readily demonstrates the site, the type and the length of the coarctation. In addition, the pressure gradient across the narrowing is measured in the catheterisation laboratory, proximal and distal to the stenosis, and the treatment strategy is determined accordingly.

In our clinic, echocardiography is performed in every patient in whom aortic coarctation is suspected, and the diagnosis is confirmed by computed tomography. Once the diagnosis has been established, aortography and pressure measurement proximal and distal to the narrowing are carried out, specifically in order to define the treatment strategy.

How is the closed (percutaneous) procedure performed?

The femoral artery in the groin is one of the main vessels through which we reach the aorta. In the angiography laboratory this artery is punctured with a small needle and a single sheath is placed in it.

Through the sheath placed in the femoral artery, the coarctation site is reached with a dedicated tube (catheter) and with specially designed, biocompatible guidewires. Once the coarcted segment has been crossed, a supportive extra-stiff guidewire is advanced through the catheter. A dedicated balloon is then passed over this guidewire and inflated gently at the level of the coarctation. Because the coarctation site in adult patients is prone to rupture, the balloon must not be inflated fully to high pressure in adults, as it is in children. After the segment has been dilated to a modest degree with the balloon, a balloon-expandable stent (a metal mesh scaffold) is implanted at that site to secure adequate patency, and the procedure is completed.

Are there any risks associated with the closed method or with the devices used?

The complication rate of this closed-method treatment is far lower than that of open surgery. In adults the coarctation has been present for a long time, and numerous collateral branches develop in an attempt to support blood flow around the narrowed segment. The presence of these collaterals increases the risk of bleeding during surgery, and undesirable complications such as stroke, paraplegia or intestinal ischaemia may arise while some of these collateral branches are being ligated.

For this reason, whereas surgical treatment takes first place in the neonatal period and in early childhood, in adulthood the closed method — balloon dilatation of the segment followed by the implantation of a stent to secure full patency — is regarded as the ideal treatment. Even when open surgical operations are indicated because of other accompanying cardiac lesions, treatment without open surgery remains the preferred approach to the coarctation itself, and it can be performed successfully, with a very low complication rate, in the majority of adults.

Complications that may arise during open surgery — major bleeding, the complications of prolonged anaesthesia, and injury to vessels and adjacent structures — are not commonly seen with the closed treatment. The cosmetic advantage of this procedure is also clear, since it is carried out without opening the chest, using only a small needle and a sheath placed in the femoral artery. After stent implantation, recurrent narrowing (recoarctation) or aneurysm formation may rarely develop at the site of the stenosis. If recurrent narrowing occurs, balloon dilatation can be repeated. Compared with open surgery, however, the occurrence of these complications is extremely rare.