Which type of dissection may extend proximally or distally, originating from the ascending aorta?

The correct answer is Type A dissection. Type A dissections originate in the ascending aorta and can extend both proximally and distally. This characteristic is critical since Type A dissections are associated with a greater risk of complications, including aortic valve involvement and pericardial tamponade, due to their location and the potential retrograde extension toward the heart.

In the classification of aortic dissections, Type A specifically refers to dissections that begin in the ascending aorta, while Type B dissections begin in the descending aorta. DeBakey classifications further specify the dissections: DeBakey Type 1 involves both the ascending and descending aorta, Type 2 is limited to the ascending aorta, and Type 3 is confined to the descending aorta. Therefore, recognizing Type A's distinction of originating from the ascending aorta is key in understanding the seriousness and potential treatment approaches for this condition.