Structure and function of the aorta in inherited and congenital heart disease and the role of MRI

The aorta is not simply a tube or conduit but a highly complex part of the vascular tree, originating from the left ventricular (LV) outflow tract and aortic valve and extending to its major thoracic and abdominal branches. Passing blood from the heart to the limbs and major organs is one functional aspect of the aorta; of equal importance is its capacity to distend and recoil in response to pulsatile flow, thereby reducing afterload for the LV and facilitating diastolic perfusion of the coronary arteries. Intrinsic aortic wall abnormalities have been described in inherited connective tissue disorders such as Marfan syndrome and bicuspid aortic valve (BAV) disease, but recent reports indicate similar aortic involvement in classical congenital heart disease (CHD) entities such as coarctation of the aorta, tetralogy of Fallot (ToF) and transposition of the great arteries (TGA).1 2 The aortic media consists of smooth muscle and an extracellular matrix that is composed of ground substance, in which elastic fibres and collagen are embedded in a hydrated gel.1 2 Smooth muscle cells govern vasodilatation and vasoconstriction, collagen provides inert aortic wall strength, and elastin permits distension and recoil in response to pulsatile flow.1 Current focus on the origin of aortic wall abnormalities has shifted towards these specific medial constituents and their crucial role in the structural and functional integrity of the aorta (figure 1).1 2 Figure 1 The elastic laminae of the aortic media provides structural support and elasticity to the aorta. In normal tricuspid valve patients (A), fibrillin-1 microfibrils tether smooth muscle cells to adjacent elastin and collagen matrix components. In patients with a bicuspid aortic valve (B), deficient microfibrillar elements result in smooth muscle cell detachment, matrix metalloproteinases release, matrix disruption, cell death, and a loss of structural support and elasticity. Reproduced with the permission …