Blood flow imaging with 3-dimensional time-resolved, phase-contrast cardiac magnetic resonance (4-dimensional [4D] Flow) is an innovative and visually appealing method for studying cardiovascular disease that allows quantification of important secondary vascular parameters including wall shear stress. The hypothesis of this pilot study is that 4D Flow will become a powerful tool for characterizing the relationship of aortic valve-related flow dynamics, especially with bicuspid aortic valve (BAV), and progression of ascending aortic (AsAo) dilation. We identified 46 patients previously studied with 4D Flow: tricuspid aortic valve patients without valvular disease (n = 20), and BAV patients with either normal flow (n = 7) or eccentric systolic jets resulting in abnormal right-handed helical AsAo flow (n = 19). The subgroup of patients with BAV and eccentric systolic AsAo blood flow was found to have significantly and asymmetrically elevated wall shear stress. This increased hemodynamic burden may place them at risk for AsAo aneurysm.

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Aortic arch hypoplasia has been linked to aneurysm formation after coarctation repair, with abnormal blood flow proposed as a mechanism (1). Time-resolved, 3-dimensional phasecontrast magnetic resonance imaging (4-dimensional flow) allowed dynamic visualization of flow and computation of vectorial wall shear stress in 5 patients after coarctation repair, 4 with arch hypoplasia (2). Symmetrical flow and wall shear stress were demonstrated in the case with normal arch geometry, whereas asymmetrically elevated systolic blood flow and wall shear stress were shown in the cases with arch hypoplasia. These findings suggest that aberrant blood flow may contribute to aneurysm formation in this context.Four-dimensional flow was used to visualize systolic blood flow and calculate wall shear stress in 5 patients after coarctation repair, 4 with arch hypoplasia. Maximum intensity projection magnetic resonance angiography is provided to demonstrate aortic arch geometry in all cases. Peak systolic velocity-coded streamlines show localized flow velocity throughout the aortic arch (Fig. 1), and cross sections show velocity and wall sheer stress at the coarctation repair site; green bars represent the magnitude of shear stress vectors. Normal systolic streamlines and symmetrical wall shear stress were demonstrated in a patient with normal arch geometry

A 35-year-old man presented with 9 years of chronic chest pain and was found to have moderate-to-severe aortic regurgitation on echocardiography. Aortic valve morphology on the initial echocardiogram was deemed normal. Computed tomography angiography was obtained for further evaluation of the aortic root dimension and anatomy. In addition to noninvasive evaluation of the coronary arteries, the higher spatial resolution and volumetric coverage of computed tomography angiography can better define the valvular and aortic anatomy. Reconstruction of retrospectively gated cine images through the aortic valve plane revealed a quadricuspid valve with 4 equal-sized cusps. Incomplete coaptation of the aortic valve cusps was seen during diastole, explaining the marked aortic regurgitation. In addition, a dilated ascending thoracic aorta (4.7 cm) was revealed. On the basis of these findings, the patient was treated surgically with a composite valve graft replacement of his aortic root.