Dissecting Aneurysms

Abstract

Dissecting aortic aneurysms develop from hemorrhage in the region of the vasa vasorum, with the formation of a hematoma and secondary intimal tear. The starting point is the ascending aorta just above the aortic valves in 65% and the descending aorta just distal to the origin of the subclavian artery near Botalli’s ligament in about 20%. Dissection originates at the aortic arch in about 15%. In the Marfan syndrome, coarctation of the aorta, and rarely in different forms of aortitis, the aortic wall is predisposed to split up into two layers, with the plane of cleavage running within the media. The most common cause, however, is arteriosclerosis occurring together with hypertension. Following an acute intimal tear, the dissection may continue on into the pelvic arteries, where the dissection lies on the left posterolateral aspect of these vessels. The left renal artery is therefore also involved in this process and is perfused through the false lumen. The dissection reaches the abdominal aorta in about 50%, leading to occlusion and ischemia of the right common iliac artery (see Fig. 15.7.1 a). Another possible complication is rupture of the outer layer with acute hemorrhagic shock and development of a hemopericardium or hematothorax if the rupture is localized further proximally. Rupture into the true lumen creates two complete lumina (Fig. 15.7.1c). This “reentry” often leads to an improvement of symptoms of ischemia or penetration. Another complication is thrombosis of the vascular lumen.