Physiologic measurements are especially critical in evaluating coarctation where the smallest cross-sectional diameter of the aorta and flow deceleration in the descending aorta measured on velocity-encoded cine MRI are excellent predictors of a hemodynamically significant stenosis [15,17]. Newer 4-D sequences may improve the evaluation of vascular flow and hemodynamics, such as shear stress, pressure gradients, and turbulence [23-25]. Because of cardiac motion, 3-D noncontrast navigator MRA, steady-state 3-D contrast- enhanced MRA, or gated first-pass contrast-enhanced MRA is preferable to evaluate the aortic root [26,27]. Nontraumatic Aortic Disease The addition of IV contrast for MRA can be beneficial in evaluating congenital aortic diseases. For example, contrast-enhanced MRA has a higher sensitivity, specificity, and accuracy for detecting obstructive aortic anomalies when compared with either TTE or MRA without IV contrast [28]. Contrast-enhanced MRA may also improve visualization of the aorta when compared with fast spin-echo sequences [29]. US Echocardiography Transthoracic TTE is a useful modality during the evaluation of congenital aortic abnormalities, given its association with cardiac abnormalities. For example, the reported incidence of bicuspid aortic valve in the setting of aortic coarctation ranges from 30% to 40% [19]. TTE is often the initial imaging modality when coarctation of the aorta is suspected [16], even though its utility can be reduced in the adult population because of its limited acoustic windows [21]. These limitations can be overcome somewhat through the use of the suprasternal view and Doppler imaging [20]. In addition to anatomic information, TTE can provide valuable physiologic parameters. For instance, Doppler can estimate peak velocities and pressure gradients across a stenosis [39,40]. TTE can also provide information regarding cardiac contractility, direction of flow, and valvular disorders [41].
Nontraumatic Aortic Disease. Physiologic measurements are especially critical in evaluating coarctation where the smallest cross-sectional diameter of the aorta and flow deceleration in the descending aorta measured on velocity-encoded cine MRI are excellent predictors of a hemodynamically significant stenosis [15,17]. Newer 4-D sequences may improve the evaluation of vascular flow and hemodynamics, such as shear stress, pressure gradients, and turbulence [23-25]. Because of cardiac motion, 3-D noncontrast navigator MRA, steady-state 3-D contrast- enhanced MRA, or gated first-pass contrast-enhanced MRA is preferable to evaluate the aortic root [26,27]. Nontraumatic Aortic Disease The addition of IV contrast for MRA can be beneficial in evaluating congenital aortic diseases. For example, contrast-enhanced MRA has a higher sensitivity, specificity, and accuracy for detecting obstructive aortic anomalies when compared with either TTE or MRA without IV contrast [28]. Contrast-enhanced MRA may also improve visualization of the aorta when compared with fast spin-echo sequences [29]. US Echocardiography Transthoracic TTE is a useful modality during the evaluation of congenital aortic abnormalities, given its association with cardiac abnormalities. For example, the reported incidence of bicuspid aortic valve in the setting of aortic coarctation ranges from 30% to 40% [19]. TTE is often the initial imaging modality when coarctation of the aorta is suspected [16], even though its utility can be reduced in the adult population because of its limited acoustic windows [21]. These limitations can be overcome somewhat through the use of the suprasternal view and Doppler imaging [20]. In addition to anatomic information, TTE can provide valuable physiologic parameters. For instance, Doppler can estimate peak velocities and pressure gradients across a stenosis [39,40]. TTE can also provide information regarding cardiac contractility, direction of flow, and valvular disorders [41].