|ECR 2018 / C-1522|
|Computed Tomography Angiography in Aortic Disease: what the surgeon needs to know.|
The aorta is the largest artery in the human body, pumping up to 200 million liters of blood through the body in an average lifetime. Thoracic aortic disease presentation ranges from asymptomatic (as in an aneurysm incidentally detected on imaging) to severe acute chest pain (as in acute aortic dissection). The recent increased prevalence of aortic disease in Western countries is a result of increased clinical awareness and longer life spans. Multidetector-row Computed Tomography (MDCT) of the aorta can be used to diagnose various acute and chronic conditions of the aorta. Modern 64 detector-row and newer-generation CT scanners can evaluate the entire aorta, including its smaller branches, with one short breath hold. Endovascular therapies are playing an increasingly important role in the treatment of aortic diseases, while surgery remains necessary in many situations.
The Thoracic Aorta (Fig. 1) extends proximally from the aortic annulus to the diaphragmatic crura distally. The thoracic aorta is subdivided into 3 parts: the ascending aorta, the arch, and the descending aorta. The Ascending Thoracic Aorta comprises the aortic root and the tubular ascending aorta. The Aortic Root lies between the aortic annulus and the sinotubular junction. The Sinuses of Valsalva arise from the aortic root. The tubular ascending aorta extends from the sinotubular junction to the brachiocephalic trunk. Approximately 3 cm of the proximal ascending aorta is within the pericardium. The coronary arteries are the only branches of the ascending aorta. The Aortic Arch extends from the brachiocephalic trunk to the origin of the left subclavian artery. The Isthmus extends from the left subclavian artery to the ligamentum arteriosum. Three branches usually arise from the aortic arch: the brachiocephalic trunk, the left common carotid artery, and the left subclavian artery. The brachiocephalic trunk divides into the right common carotid artery and the right subclavian artery.
References: Piazza N. et al. Circulation: Cardiovascular Interventions. 2008;1:74-81
Acute Aortic Syndrome is a group of aortic pathologies that are acute emergencies. Underlying aortic diseases include penetrating atherosclerotic ulcer, intramural hematoma, aortic dissection, rupturing aneurysms and traumatic aortic injury. The aortic wall consists of 3 layers (tunica intima, tunica media, and adventitia). Acute Aortic Dissection is presumed to occur when an intimal tear develops, permitting entry of blood to a diseased underlying media characterized by elastic degeneration and smooth muscle cell loss (Fig. 2). Chronic acquired conditions, such as systemic arterial hypertension, sometimes in combination with atherosclerosis, cause thickening and fibrosis of the intimal layer and degradation and apoptosis of smooth muscle cells in the media. These processes lead to necrosis and fibrosis of the elastic components of the arterial wall, which in turn produce wall stiffness and weakness, from which dissection and rupture may arise. Chronic arterial hypertension has been widely accepted as the most common acquired condition that leads to dissection of the aorta from high shear stress. Nearly 75% of patients with AAD have an history of hypertension. Other acquired conditions that have been associated with AAD include direct blunt trauma, tobacco use, hyperlipidemia, cocaine (including crack cocaine) use, and pregnancy.
References: Braunwald’s Heart Disease VII Edition – 2007 Elsevier Masson srl.
Aortic Dissections can be classified according to involvement of the ascending aorta or arch. This involvement implies a worse prognosis and usually requires surgical management. The DeBakey and Stanford classification systems are the most commonly used systems to categorize aortic dissections and they are based on location (Fig. 3).
References: ESC Guidelines on the diagnosis and treatment of aortic diseases - European Heart Journal (2014) 35, 2873–2926
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