Dissecting aorta: A simple explanation

MANILA, Philippines - The aorta is the largest artery in the body, around 3 centimeters in diameter. It is shaped like a walking cane, which starts from the heart, curves up a bit and goes on a u-turn down to the chest cavity and abdomen area. Unlike a walking cane, however, the aorta is softer and fleshier in consistency, which is important for it to withstand the powerful surge of blood pumped by the heart.

The upper part of the aorta (the “u” part) is called the ascending aorta. The middle part in the chest area is called the thoracic aorta, while the aorta in the abdomen area is called the abdominal aorta.

Its elastic wall is made up of three protecting linings. The inner and thinner wall is called intima, the middle wall is termed media, and the outer wall is called adventitia.

What is an aortic dissection?

If there is too much pressure inside the aorta (like a blood pressure of 180/100), the inner part of the aorta (the intima wall) can tear up, thereby causing the blood to flow through a flap created by the loosening of the inner wall. This condition is known as an aortic dissection, a dangerous situation needing urgent medical and possible surgical treatment.

Depending on the location of the tear in the aorta, the condition is named appropriately, like thoracic aortic dissection, if the tear is in the thoracic part of the aorta.

Not a heart attack?

A common mistake, even by doctors, is to label an aortic dissection as a heart attack. Although the patient may complain of the same back and chest pain, the two diseases are very different.

A heart attack involves a blockage in the small arteries attached to the heart, while an aortic dissection involves a tear in the wall of the largest artery of the body. In some unfortunate situations, the patient can have both conditions especially if the tear in is the ascending part of the aorta.

Who are at risk?

Usually, an aortic dissection does not occur spontaneously but is brought about by years of wear and tear on the aorta. The most important risk factor is high blood pressure. If the blood pressure is constantly above the upper limit of 140 over 90, this can initially lead to a ballooning of the aorta (called an aortic aneurysm), and later to an aortic dissection.

The peak incidence of aortic dissection occurs between 50 to 65 years old. Other risk factors include high cholesterol, smoking, cocaine use and traumatic injuries to the chest or abdomen.

How to detect and treat aortic dissection?

The main symptom of aortic dissection is excruciating pain in the back or abdominal area, depending if the dissection is in the thoracic or abdominal aorta, respectively. Since the aorta supplies the arteries to the arms and legs, the patient may have weak pulses and unequal blood pressures. Dizziness, loss of consciousness, and numbness and paralysis of various parts of the body may also occur.

To diagnose aortic dissection, doctors request a CT Scan or an MRI of the chest and/or abdomen. If this test is negative, a more invasive test called an aortography may be carried out. Aortography involves inserting a special wire inside the aorta and uses contrast dye to detect the dissection.

Treatment of aortic dissection involves two strategies: aggressive medical therapy to lower the blood pressure and possible surgical intervention to repair the defect.

Since the most crucial factor that favors dissection is the systolic blood pressure (the first number of the blood pressure), doctors prescribe drugs called beta-blockers to decrease the force of the heart’s pumping.

Surgery may be needed in complicated cases, such as blockage in the arteries of the limbs, persistent pain, and ballooning of the aorta with danger of a full-blown rupture. That is why this condition is sometimes called a “walking time bomb” since we don’t know when the rupture will occur.

Dissecting aorta by the numbers?

Since no one can determine when a dissecting aorta will happen, doctors rely on data showing the percentages of such occurrence.

Around 1 in 5 patients with aortic dissection die before reaching the hospital. Without treatment, the mortality rate is 25 percent in one day, 50 percent in one week, 75 percent in one month, and 90 percent in three months.

When the patient reaches the hospital, the mortality rate is about 30 percent for a dissection of the ascending and thoracic aorta, and 10 percent for the abdominal aorta.

For the patients who survive the acute episode, survival rate is around 60 percent in 5 years and 40 percent in 10 years.

The most important late complications are redissection and formation of a localized weakness in the aorta. These conditions are serious and may need surgical repair.