Arterial Aneurysms - Aortic Dissection

Question 1

What is an aortic dissection?

Answer 1

A break or tear forms in the inner layer of the aorta (to create a ‘false lumen’) between the tunica intima and tunica media of the aorta.

Question 2

What are the three layers of the aorta (or any blood vessel)?

Answer 2

1. Tunica Adventitia.
2. Tunica Media.
3. Tunica Intima.

Question 3

Which part of the aorta is most affected by aortic dissection? (2)

Answer 3

1. Ascending Aorta and Aortic Arch.

2. Right Lateral Area of Ascending Aorta - under most stress from blood exiting the heart.

Question 4

Stanford System of Classification of Aortic Dissection.

Answer 4

1. Type A - ascending aorta (before brachiocephalic artery) - 2/3 of cases.
2. Type B - descending aorta (after subclavian artery) - 1/3 of cases.

Question 5

DeBakey System of Classification of Aortic Dissection.

Answer 5

Type I - begins in ascending aorta and involves at least aortic arch.
Type II - ascending aorta only.
Type IIIA - begins in descending aorta above diaphragm.
Type IIIB - begins in descending aorta and involves below diaphragm.

Question 6

What happens if the dissection extends proximally?

Answer 6

Aortic Valve Incompetence - Inferior MI, Cardiac Arrest.

Question 7

Mechanisms of Disease from Aortic Dissection (2).

Answer 7

1. Blood tracks through false lumen - reduced flow through true lumen - ischaemia/infarction.
2. Rupture externally into pleural/pericardial/abdominal cavity.

Question 8

Risk Factors of Aortic Dissection (5).

Answer 8

1. Hypertension (Major).
2. Connective Tissue Disorder (Major).
3. Pregnancy (Major).
4. Triggers of Dramatic Increase in BP e.g. Heavy Weightlifting, Cocaine Use.
5. Same risk factors of Peripheral Arterial Disease.

Question 9

Give 4 conditions/procedures of the aorta that increase the risk of dissection.

Answer 9

1. Bicuspid Aortic Valve.
2. Coarctation of the Aorta.
3. Aortic Valve Replacement.
4. CABG (Coronary Artery Bypass Graft).

Question 10

Clinical Presentation of Aortic Dissection (7)

Answer 10

1. Sudden-Onset, Severe, ‘Ripping’/’Tearing’ Pain.
   2 Ascending Aorta - Anterior (Chest) Pain; Descending Aorta - Posterior (Between Shoulder Blades) Pain.
2. Hypertension.
3. Differences in BP between arms (more than 20).
4. Radial Pulse Deficit.
5. Neurological Deficit (if carotid artery is affected)
6. Diastolic Murmur.

Question 11

Investigations of Aortic Dissection (3).

Answer 11

1. CXR - Widened Mediastinum.
2. Initial - CT Angiogram (False Lumen) - preferred in stable patients.
3. TOE (Transoesophageal Echocardiography) - preferred in unstable patients.

Question 12

Management of Type A Patients (3).

Answer 12

1. Open Surgery (Midline Sternotomy) - remove section of aorta with defect and replace with synthetic graft.
2. Aortic valve may need to be replaced.
3. Aim for BP Systolic between 100-120 whilst awaiting intervention.

Question 13

Management of Type B Patients (2).

Answer 13

1. Conservative with Bed Rest and Antihypertensive IV Labetalol.
2. If required, EVAR (Thoracic Endovascular Aortic Repair).

Question 14

Complications of Aortic Dissections (5).

Answer 14

1. MI - Coronary Dissection (Backward Tear, Inferior Pattern, RCA involvement usually).
2. Stroke - Carotid Dissection (Forward Tear).
3. Paraplegia - Anterior Spinal Artery (Forward Tear).
4. Cardiac Tamponade (Tracks back to aortic root and pericardial rupture).
5. Aortic Valve Regurgitation (involving root causing stretching aortic valve).

Question 15

What is important about the management of an MI that presents with dissection?

Answer 15

Treatment of the MI e.g. thrombolysis can cause fatal progression of the dissection.