Aortic Dissection
· Predisposing factors o Hypertension (most commonly) o Atherosclerosis o Cystic medial necrosis § Marfan’s syndrome o Coarctation of the aorta o Aortic stenosis o S/P prosthetic aortic valve o Trauma (rare) o Pregnancy (rare) · Aneurysm defined by size criteria o In general, ascending aorta > 5 cm o Descending aorta > 4 cm · Vessels involved with dissection o Any artery can be occluded o Usually the right coronary and three arch vessels are involved with arch aneurysms o Right pulmonary artery and left-sided pulmonary veins may be occluded · Types o DeBakey Type I § Involves entire aorta o DeBakey Type II § Least common · Ascending aorta only o DeBakey Type III § Most common · Descending aorta only
o Stanford Type A § Ascending aorta involved · Over half develop aortic regurgitation o Stanford Type B § Ascending aorta NOT involved · Most dissections arise either just distal to the aortic valve or just distal to aortic isthmus · True versus false channel o False channel usually arises anterior in the ascending aorta and spirals to posterior and left lateral in descending aorta o True channel is usually larger o Slower flow in false channel on MR
*Goal is to prevent backward involvement of the aortic valve or rupture into pericardium · Clinical o Sharp, tearing, intractable chest pain o Murmur or bruit of aortic regurgitation o Previously hypertensive, now possible shock o Asymmetric peripheral pulses o Pulmonary edema · Imaging Findings o Chest films § Mediastinal widening § Left paraspinal stripe § Displacement of intimal calcifications § Apical pleural cap § Left pleural effusion § Displacement of endotracheal tube or nasogastric tube o MRI § Intimal flap § Slow flow or clot in false lumen o CT § Intimal flap § Displacement of intimal calcification § Differential contrast enhancement of true versus false lumen
CT of abdominal aorta shows intimal flap (dark line -red arrow)
o Angiography § Intimal flap § Double lumen § Compression of true lumen by false channel § Increase in aortic wall thickness > 10 mm § Obstruction of branch vessels · Diagnosis o MRI if available is usually best for imaging ascending aorta o Contrast-enhanced CT can image arch and descending aorta o Transesophageal ultrasound, if available, especially for root and ascending aorta o Angiography · Prognosis
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