As you can see in the diagram above, the wall of the Aorta consists of three layers; the Intima, the Media, and the Adventia.

An aortic dissection is a tear in the inner layer of the aortic wall. Take a look at the slide show animation below for an illustration of aortic dissection.

The tear in the wall allows blood to enter and separate the inner and outer layers of the aorta. As the blood gets trapped between the two layers, this weakens the outer wall, stretching it out to the degree that it looks like a balloon (aneurysm), which may rupture.

Sometimes however the blood, which is now trapped between the aortic layer, may move and compress on vital arteries, which happen to originate from the aorta close to that area. If the coronary arteries are compressed this cuts off the blood supply to the heart muscle and cause a heart attack (myocardial infarction).

If the arteries to brain are compressed this will diminish the blood flow to the brain, resulting in loosing consciousness and having a brain attack (stroke), compressing the kidney arteries will result in the death of kidney cells (kidney failure). and so on.

Weakness of the aortic wall will also distort the support that it provides to the aortic valve, it is like forcing apart the walls which support the frame of a double door, as you can imagine the door sides will separate away and result in a big gap.

In the case of the of the aortic valve, this results in a huge blood leak backwards (insufficiency or regurgitation), because of this tremendous back flow leak to the heart, the heart muscle will not be able to generate enough force to handle such a sudden change.

The heart will then swell (large heart) and lose its ability to push the blood forward to the body (Congestive heart failure). This is also very important because most Aortic Dissections in Marfan Syndrome occur in the aortic wall just above the aortic valve.

Aortic Dissection is the primary cause of death in individuals
with the Marfan syndrome.