Types of Aortic Dissection

The aorta—a candy cane–shaped blood vessel originating in the chest at the top of the heart and extending into the abdomen—is the largest artery in the body. Like other arteries, it carries oxygen-rich blood from the heart to the rest of the body. The walls of the aorta consist of three layers that give it strength.

An aortic dissection, or tear in the aorta, typically occurs when the inner layer of the artery’s wall weakens. If left untreated, the tear can enlarge. When this happens, blood can pass through the tear into the middle layer of the wall, causing the layers to separate from one another, or dissect. This can lead to the formation of a new channel, called a false lumen, between the two layers. This false lumen can extend from the tear to the lowest part of the aorta, preventing blood from flowing properly to the rest of the body.

The separation of the inner layer of the aorta forms a flap, called a septum, which can have multiple holes, known as reentry tears, that have a Swiss cheese appearance. These tears allow blood to flow between the true lumen, or natural passageway, and the false lumen. If the flap doesn’t peel away from the aorta, blood can pool in the false lumen.

Over time, the blood in the false lumen can back up and clot, cutting off blood flow to other organs and further weakening the aortic wall. Sometimes, the blood breaks through the outer layer of the aorta, causing a life-threatening loss of blood and drop in blood pressure that requires immediate surgery.

Aortic dissections that occur in the ascending part of the aorta are called type A; those in the descending aorta are type B. These types of dissections are further classified by two categories: acute and chronic.

Acute and Chronic Aortic Dissections

Doctors diagnose both type A and type B aortic dissections as being either acute or chronic. Acute dissections cause life-threatening symptoms and require emergency medical care. Chronic dissections are less serious, but still require treatment.

Acute Aortic Dissection

Acute aortic dissection causes sudden chest or back pain or both, and requires immediate surgical treatment to avoid rupture of the aorta. NYU Langone cardiac surgeons are highly experienced in open surgical procedures to repair an acute aortic dissection.

Chronic Aortic Dissection

Sometimes symptoms of an aortic dissection are vague and nonspecific and may go unnoticed until the tear begins to cause other symptoms, such as sweating, shortness of breath, or fainting. When these symptoms occur, or if imaging tests show signs that the condition has been present two weeks or longer, it is called chronic aortic dissection.

Chronic dissection is monitored with CT scans or a type of MRI scan called a magnetic resonance angiogram. These imaging tests can reveal a rapid expansion of the aorta, which can signify a blood clot or an aortic aneurysm, in which the aorta bulges, necessitating surgery. Doctors often prescribe medications to help reduce the flow of blood against the aortic wall.

Type A Aortic Dissection

Type A aortic dissection occurs in the ascending aorta, which is the curved part of the aorta that extends upward from the heart. This tear may extend along the upper part of the aorta and down toward the abdomen. Type A is the most common type of aortic dissection and is more likely to be acute than chronic. This makes it more dangerous than type B dissections because it is more likely to cause the aorta to rupture, leading to a potentially fatal heart condition.

People with type A aortic dissection often report shortness of breath and a sudden, severe, sharp pain that feels like a tearing in the chest and upper back. However, some people experience no symptoms.

Type B Aortic Dissection

Type B aortic dissection originates in the descending aorta, which extends from the arch at the top of the ascending aorta—the part that extends upward from the heart—to the bottom section of the aorta, also known as the abdominal aorta.

Most type B aortic dissections are chronic and therefore rarely causes life-threatening side effects. Usual treatments include medication and routine checkups with your doctor. Occasionally, type B dissections can reduce or block blood flow to organs, such as the kidneys and the intestines. When this occurs, our vascular surgeons use endovascular surgery to place a stent graft to support the aorta while also preserving blood flow to nearby organs.

Symptoms may include high blood pressure and a severe, sharp back pain that can feel like it is extending into the chest or abdomen.

Chronic Dissection with Aneurysm

In some situations, a chronic type B dissection can lead to an aneurysm, which is a bulge in the aortic wall that can lead to a dangerous aortic rupture. Treatment for aortic dissection with aneurysm depends on where it occurs along the descending aorta and on whether the rupture has a genetic cause, such as a connective tissue disorder like Marfan syndrome. These difficult-to-treat conditions often require advanced surgical care from the team at NYU Langone’s Aortic Center.

Complications of Aortic Dissection

Aortic dissection can lead to serious complications, including heart attack, kidney failure, stroke, paralysis, and intestinal ischemia, in which blood vessels to the intestines become blocked. It can also cause lower extremity ischemia, or blockages in the blood vessels of the legs.

Each of these complications initiate in a different portion of the aorta. Because the risks and appropriate treatments can be markedly different depending on the type of aortic dissection, it is crucial to accurately diagnose this condition.