Aortic coarctation

December 31, 2014

Synonyms

Overview

A rare inherited birth defect where the heart blood vessel called the aorta has a narrowed area which affects blood flow. It is in the area where the ductus arteriosus (ligamentum arteriosum after regression) inserts. The word "coarctation" means narrowing. Coarctations are most common where the aorta—the major artery leading away from the heart—arches toward the abdomen and legs (the aortic arch). The arch may be small in babies with coarctations. Other heart defects may also occur when coarctation is present, typically occurring on the left side of the heart. When a patient has a coarctation, the left ventricle has to work harder. Since the aorta is narrowed, the left ventricle must generate a much higher pressure than normal in order to force enough blood through the aorta to deliver blood to the lower part of the body. If the narrowing is severe enough, the left ventricle may not be strong enough to push blood through the coarctation, thus resulting in lack of blood to the lower half of the body. Physiologically its complete form is manifested as interrupted aortic arch. The degree of constriction is variable which mild cases asymptomatic until adulthood. The poor blood flow to the lower body gives results in it appearing less developed than that upper body.

Symptoms

In mild cases, children may show no signs or symptoms at first and their condition may not be diagnosed until later in life. Some children born with coarctation of the aorta have other heart defects too, such as aortic stenosis, ventricular septal defect, patent ductus arteriosus or mitral valve abnormalities.
Coarctation is about twice as common in boys as it is in girls. It is common in girls who have Turner syndrome.
Symptoms may be absent with mild narrowings (coarctation). When present, they include: difficulty breathing, poor appetite or trouble feeding, failure to thrive. Later on, children may develop symptoms related to problems with blood flow and an enlarged heart. They may experience dizziness or shortness of breath, faint or near-fainting episodes, chest pain, abnormal tiredness or fatigue, headaches, or nosebleeds. They have cold legs and feet or have pain in their legs with exercise (intermittent claudication).
In more severe cases, where severe coarctations, babies may develop serious problems soon after birth because not enough blood can get through the aorta to the rest of their body. Arterial hypertension in the arms with low blood pressure in the lower extremities is classic. In the lower extremities, weak pulses in the femoral arteries and arteries of the feet are found.

Other symptoms include:

Cold feet or legs
Decreased ability to exercise
Poor growth Note

Causes

The aorta carries blood from the heart to the vessels that supply the body with blood and nutrients. If part of the aorta is narrowed, it is hard for blood to pass through the artery. Aortic coarctation is more common in persons with certain genetic disorders, such as Turner syndrome. However, it can also be due to birth defects of the aortic valves. Aortic coarctation is rare. It is usually diagnosed in children or adults under age 40.

Prevention

There is no known way to prevent this disorder, because they are usually present at birth. The best thing for patients who are affected by this disease is early detection. Some signs that can lead to a coarctation have been linked to pathologies such as Turner syndrome, bicuspid aortic valve, and other family heart conditions. however, awareness of risk may make early diagnosis and treatment possible.

Diagnosis

With imaging, resorption of the lower part of the ribs may be seen, due to increased blood flow over the neurovascular bundle that runs there. Poststenotic dilatation of the aorta results in a classic 'figure 3 sign' on x-ray. The characteristic bulging of the sign is caused by dilatation of the aorta due to an indrawing of the aortic wall at the site of cervical rib obstruction, with consequent poststenotic dilatation. This physiology results in the '3' image for which the sign is named. 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.

Coarctation of the aorta can be accurately diagnosed with magnetic resonance angiography. In teenagers and adults echocardiograms may not be conclusive. In adults with untreated coarctation, blood often reaches the lower body through collaterals, e.g. internal thoracic arteries via the subclavian arteries. Those can be seen on MR, CT or angiography. An untreated coarctation may also result in hypertrophy of the left ventricle.

Arteries can be checked for narrowing by the cardiologist by using an CT angiogram. This test is very easy on the patient because it is a minimally invasive procedure. The first step in the process is having a dye injected into the patient to help highlight the arteries for the CT scanner. While the CT scanner is imaging the arteries, images will be able to be viewed by the cardiologists almost immediately.

An MRI scan is a test that uses a magnetic field and pulses of radio wave energy to make pictures of the body. An MRI of your chest will reveal the location of the coarctation of the aorta and determine whether it affects other blood vessels in the body.

Cardiac catheterization is an invasive imaging procedure that is a tool for evaluating heart functions in real time. A long, narrow tube called a catheter is inserted through a plastic hollow tube called an introducer sheath. The introducer sheath is typically inserted into the patients arm or leg. The catheter is positioned through the patients blood vessel until it reaches the coronary arteries. Once the catheter is in position, a contrast dye is injected though the tip of the catheter while x-rays are taken to follow the dye through the chambers of the heart and arteries. This part of the procedure is called the coronary angiogram. Coronary artery disease (CAD) occurs when there is a narrowing or blockage of the arteries leading to or from the heart. The cardiac catheterization is an interventional procedure that opens up the coronary artery to increase the blood flow to the heart. The contrast material injected into the arteries that help produce images of the heart help locate narrowed or blocked areas in arteries around the heart. There are other ways to produce images such as intra-vascular ultrasound (IVUS) and fractional flow reserve. These two different procedures give cardiologists more diverse options to best suit the patients needs.

Prognosis

Coarctation of the aorta can be cured with surgery. Symptoms quickly get better after surgery. However, there is an increased risk for death due to heart problems among those who have had their aorta repaired. But, without treatment, most people die before age 40. For this reason, doctors usually recommend that the patient has surgery before age 10. Most of the time, surgery to fix the coarctation is done during infancy.

Side Effects:
Hypertension is defined when a patient's blood pressure in the arm exceeds 140/90 mmHg under normal conditions. This is a severe problem for the heart and can cause many other complications. In a study of 120 coarctation repair recipients done in Groningen, The Netherlands, twenty-nine patients (25%) experienced hypertension in the later years of life due to the repair. While hypertension has many different factors that lead to this stage of blood pressure, people who have had a coarctation repair — regardless of the age at which the operation was performed — are at much higher risk than the general public of hypertension later in life. Undetected chronic hypertension can lead to sudden death among coarctation repair patients, at higher rates as time progresses.

Angioplasty is a procedure done to dilate an abnormally narrow section of a blood vessel to allow better blood flow. This is done in a cardiac catheterization laboratory. Typically taking two to three hours, the procedure may take longer but usually patients are able to leave the hospital the same day. After a coarctation repair 20-60% of infant patients may experience reoccurring stenosis at the site of the original operation. This can be fixed by either another coarctectomy.

Coronary artery disease (CAD) is a major issue for patients who have undergone a coarctation repair. Many years after the procedure is done, heart disease not only has an increased chance of affecting coarctation patients, but also progresses through the levels of severity at an alarmingly increased rate. In a study conducted by Mare Cohen, MD, et al., one fourth of the patients who experienced a coarctation died of heart disease, some at a relatively young age.

Clinical criteria are used in most studies when defining recurrence of coarctation (recoarctation) when blood pressure is at a difference of >20 mmHg between the lower and upper limbs. This procedure is most common in infant patients and is uncommon in adult patients. In a study conducted by Koller et al., 10.8% of infant patients underwent recoarctations at less than two years of age while another 3.1% of older children received a recoarctation.

People who have had a coarctation of the aorta are likely to have bicuspid aortic valve disease. Between 20% and 85% of patients are affected with this disease. Bicuspid aortic valve disease is a big contributor to cardiac failure, which in turn makes up roughly 20% of late deaths to coarctation patients.

Follow-up:
Leaving the hospital after a coarctation procedure is only one step in a lifelong process. Just because the coarctation was fixed does not mean that the patient is cured. It is extremely important to visit the cardiologist on a regular basis. Depending on the severity of the patient's condition, which is evaluated on a case-by-case level, visiting a cardiologist can be a once a year surveillance check up. Keeping a regular schedule of appointments with a cardiologist after a coarctation procedure is complete helps increase the chances of survivability for the patients.

Treatment

Surgery is usually recommended. The narrowed part of the aorta will be removed or opened. If the problem area is small, the two free ends of the aorta may be re-connected. This is called anastomosis. If a large part of the aorta was removed, a Dacron graft (a synthetic material) or one of the patient's own arteries is used to fill the gap. A tube graft connecting two parts of the aorta may also be used. Sometimes, balloon angioplasty may be done instead of surgery. In some cases angioplasty can be performed to dilate the narrowed artery.

For fetuses at high risk for developing coarctation, a novel experimental treatment approach is being investigated, wherein the mother inhales 45% oxygen three times a day (3 x 3–4 hours) beyond 34 weeks of gestation. The oxygen is transferred via the placenta to the fetus and results in dilatation of the fetal lung vessels. As a consequence, the flow of blood through the fetal circulatory system increases, including that through the underdeveloped arch. In suitable fetuses, marked increases in aortic arch dimensions have been observed over treatment periods of about two to three weeks.

The long term outcome is very good. Some patients may, however, develop narrowing (stenosis) or dilatation at the previous coarctation site. All patients with unrepaired or repaired aortic coarctation require follow up in specialized Congenital Heart Disease centers.