Aortic dilatation in patients with prosthetic aortic valve: comparison of MRI and echocardiography

Patients with prosthetic aortic valve have an increased risk for aortic dissection, which rises further with growing aortic diameters. Thus, accurate aortic monitoring is required. As transthoracic echocardiography (TTE), the current clinical standard, is frequently restricted to the proximal ascending aorta, the use of two-dimensional cardiovascular magnetic resonance (2D-CMR) in transverse orientation was investigated as a screening tool to assess ascending aortic dimensions.

Fast, non-contrast-enhanced, non-breath-hold, steady-state free-precession (SSFP) sequences (1.5 Tesla, slice thickness 7 mm, gap 1.8 mm, scan time 10-15 s) were applied to image the thorax in transverse planes. To test the accuracy of aortic dimensions obtained in this way, comparison was made to contrast-enhanced three-dimensional MR angiography (3D-MRA) as the 'gold standard' in 30 patients with aortic or aortic valve disease. After validation, transverse 2D-CMR was used to assess ascending aortic dimensions in 65 patients with aortic bioprostheses, and the results were compared to those acquired with TTE.

Data acquired with both 2D-CMR and 3D-MRA agreed well when assessing ascending aortic diameters (r = 0.99; p < 0.001; mean difference 0.1 +/- 0.1 cm). In patients with bioprostheses, the image quality was diagnostic in 100% of cases for 2D-CMR, and in 93.4% for TTE. The ascending aortic diameter by 2D-CMR (mean 3.8 +/- 0.5 cm; range: 2.6-5.0 cm) was larger (p < 0.001) than by TTE (3.3 +/- 0.6 cm; range: 2.3-4.9 cm). Aortic dilatation (diameter, indexed by body surface area, > 2.1 cm/m2) was present in 38.5% of 2D-CMR cases and in 11.5% of TTE cases. The intra- and inter-observer variabilities to assess aortic dimensions by 2D-CMR were 2.1 +/- 1.9% and 4.3 +/- 3.7%, respectively.

Imaging of the complete thorax in transverse orientation using fast, non-contrast-enhanced SSFP images provided an accurate and reliable approach to screen for aortic dilatation. In patients with aortic bioprostheses, 2D-CMR revealed a high prevalence of aortic dilatation, which was considerably underestimated by TTE.