Which condition is characterized by a sudden tear in the aorta?

Aortic dissection is characterized by a sudden tear in the aorta, specifically in the inner layer of the vessel. This tearing allows blood to flow between the layers of the aorta, creating a separation or "dissection" of the aortic wall. This condition can lead to serious complications, including decreased blood flow to vital organs, rupture of the aorta, and often results in severe pain that is typically described as a tearing or ripping sensation.

In contrast, aortic stenosis involves the narrowing of the aortic valve, which impairs blood flow from the heart to the rest of the body but does not involve a tear in the aorta itself. Aortic regurgitation is the backflow of blood into the heart due to improper closure of the aortic valve, again not related to a tear in the aorta. An aortic aneurysm refers to a bulge in the aorta caused by weakness in the vessel wall, which can also lead to rupture but is not synonymous with a tear. Thus, aortic dissection is the condition specifically defined by the sudden tear in the aorta.