Glossary of Terms
A condition of the aorta in which the inner layer of the aorta tears, allowing the blood flowing across the tear to enter the tear and flow between the layers of the aorta. As the blood travels between the layers of the aorta the blood is separating or "dissecting" the layers of the aorta. The aorta is made up of 3 layers. When the inner layer tears, the blood dissects the intima away from the outer two layers. The cause of the intimal tear can be high blood pressure, atherosclerosis, or trauma. Aortic dissections can occur in any portion of the aorta and can become serious or life-threatening. Although they are not true aneurysms, dissections are sometimes referred to as aneurysms or dissecting aneurysms because they can expand and resemble aneurysms of the aorta. Dissections of the ascending aorta and aortic arch are considered surgical emergencies. Dissections of the descending thoracic aorta are often treated medically, but may require surgery depending on certain indications.
How aortic dissections are classified
The Stanford System classifies aortic dissections based on whether the ascending aorta is involved.
- Stanford Type A (Ascending Aorta) - Type A dissections come right out of the heart. The tear from Type A dissections can cut off the coronaries — the arteries that surround and supply the heart. It can also cause a stroke and cut off the carotids (the two main arteries that carry blood to the head, neck and brain and their two main branches).
- Stanford Type B (Descending Aorta) - Type B dissections are descending thoracic aorta dissections. The thoracic aorta is the part of the aorta located in the thorax. Type B dissections can get aneurysmal, which is when the artery becomes excessively enlarged due to the weakening of the artery wall. They can also cut off blood flow to vessels of the abdomen or legs. They can also become big and risk rupturing, which causes death.
The DeBakey System classifies aortic dissections based on the location of the original intimal tear:
- DeBakey Type I – originates in ascending aorta, and propagates at least to the aortic arch and often beyond it distally. It is most often seen in patients less than 65 years of age and is the most lethal form of the disease.
- DeBakey Type II – originates in the ascending aorta and is confined to it.
- DeBakey Type III – originates in the descending aorta and rarely extends proximally, but will extend distally. It most often occurs in elderly patients with atherosclerosis and hypertension.
Related article: Aortic Dissection is a Serious Condition That Can Lead to Instant Death