Aortic dissection

The aorta is the largest blood vessel in your body, and it is responsible for carrying blood from the heart to all other parts of the body. It forms a candy cane shape in the body, with the first part coming up out of the heart, the arch turning in the chest, and the longer part extending through the chest and abdomen before dividing into blood vessels to supply your legs. It is made up of the following parts:

• Aortic Root: This is the part of the aorta that connects to the heart via the aortic valve, a one-way valve that opens when the heart ejects blood, and closes when the heart relaxes to prevent blood from going backwards. From it arise the arteries that supply your heart, your ‘coronary arteries’ and there is one to supply the left, and one to supply the right.
• Ascending Aorta: This is the part of the aorta that rises up out of the aortic root, and carries blood towards the head. It is one of the more common places to have a thoracic aortic aneurysm. Please follow this link to learn about aneurysms.
• Aortic Arch: This is the curved part of the 'candy cane'. From it come branches that supply the head and the arms. It connects the ascending aorta to the descending aorta.
• Descending ‘Thoracoabdominal’ Aorta: This part goes down towards the abdomen and eventually splits to give arteries that supply the legs. It has many small branches that supply the spinal cord, and the organs in the abdomen. It has two parts:
  • Descending Thoracic Aorta: This is the part that is located in the chest, above the diaphragm.
  • Abdominal Aorta: This is the part that is located in the abdomen, below the diaphragm. It gives off blood vessels to the abdominal organs, such as the intestines, liver, spleen and kidneys. It splits to give arteries that supply the legs, called the ‘common iliac arteries’.

Arteries are made up of three layers. An aortic dissection occurs when there is a tear in the innermost layer, or lining, of the aorta, causing blood to track in between the layers. It commonly occurs in people who have aortic aneurysms, a weakening and subsequent dilatation of the aorta. Please follow this link to learn more about aneurysms.

There are two types of aortic dissection depending on which part of the aorta is involved.

• Type A Dissection: This involves a tear in the ascending aorta. It can often extend throughout the entire aorta.
• Type B Dissection: This involves a tear in the descending aorta. Sometimes, it can extend backwards into the ascending aorta.

Anuerysms often grow very slowly, and typically grow without causing any symptoms. Often, they are found in patients who are being investigated for other tests. At some point, the inner wall of the aorta becomes too weak and tears. This causes an aortic dissection.

However, aortic dissections can occur for other reasons, though less commonly. This includes trauma, particularly high speed motor vehicle collisions, or iatrogenic, meaning a complication of a medical procedure.

There are a number of risk factors that can increase your risk of developing an aneurysm over time, which therefore increases your risk of an aortic dissection. These risk factors include:

• Age – typically, aneurysms occur in people over 60-65 years of age
• Gender – aneurysms occur more commonly in men
• Smoking – this is one of the strongest risk factors for developing aneurysms
• High blood pressure – this can weaken or damage the walls of blood vessels
• High cholesterol
• Genetic conditions and connective tissue disorders – some common genetic disorders associated with aneurysms include Marfan Syndrome, Loeys-Dietz Syndrome, Ehlers-Danlos Syndrome, Familial Aortopathy Syndromes, Turner Syndrome
• Having a bicuspid aortic
• Inflammatory disorders – some examples include Takayasu Arteritis, Giant Cell Arteritis, Systemic Lupus Erythematosus. These cause the blood vessels to become inflamed.
• Infectious disorders – some examples include syphilis, fungal infections, bacterial infection
• Traumatic injury

As aneurysms grow, they usually do not cause any symptoms. However, once they reach a large enough size, or if they expand too quickly, they can cause an aortic dissection. The symptoms typically include:

• Severe, tearing chest or back pain
• Loss of consciousness
• Difficulty speaking, loss of vision, or paralysis of one or more extremities
• Shortness of breath
• Severe abdominal pain
• Severe pain in an arm or leg associated with it feeling cold

Type A dissections are referred to as a ‘surgical emergency’. They require open heart surgery to fix, and usually are fixed within hours of presenting to the hospital. A surgeon will remove the part of the aorta that has the dissection, and will replace it with a synthetic graft. Sometimes the aortic valve will also need to be replaced if it has been damaged by the aortic dissection.

Type B dissections are often treated with blood pressure control. Usually, they will prescribe medication to help lower your heart rate and blood pressure. However, surgery may be required in instances where the aortic dissection is associated with a complication. This is usually when the blood supply to another part of the body has been obstructed. In this situation, minimally invasive ‘endovascular’ procedures may be used to treat your aortic dissection. These devices help open the blocked arteries.

Hybrid surgery

Sometimes, your aortic dissection can be treated with a hybrid approach. This uses a combination of both open surgical techniques and minimally invasive, ‘endovascular’, techniques. Your healthcare providers will be able to discuss if you are a candidate for this type of procedure.

Here at Sunnybrook, we have created a hybrid OR to facilitate these procedures.

Once you have an aortic dissection, it typically becomes a lifelong issue. The aortic dissection causes a weakening of the aorta, which predisposes the aorta to the formation of aneurysms throughout its length. Your healthcare providers will request yearly imaging in order to evaluate your aorta for any changes in size. They will complete CT or MRI scans and echocardiograms to evaluate both the aorta and your heart’s function.

If the aorta does grow over time, you may need to have open or ‘endovascular’ surgery to repair it. The team at Sunnybrook has extensive experience and expertise and experience in monitoring and surgically repairing these aneurysms.

Following your aortic dissection, you will be prescribed medication to control your heart rate and blood pressure. You will also be asked to subscribe to an exercise regimen that limits physical straining.

• Genetic Aortic Disorders Association Canada
• Society for Vascular Surgery
• American Association for Thoracic Surgery
• Canadian Cardiology Society
• Society of Thoracic Surgeons
• Heart.org: What is an aneurysm