Clinical assessment of aortic valve stenosis: Comparison between 4D flow MRI and transthoracic echocardiography

BACKGROUND: The prevalence of valvular aortic stenosis (AS) increases as the population ages. Echocardiographic measurements of peak jet velocity (V(peak)), mean pressure gradient (P(mean)), and aortic valve area (AVA) determine AS severity and play a pivotal role in the stratification towards valvular replacement. A multimodality imaging approach might be needed in cases of uncertainty about the actual severity of the stenosis. PURPOSE: To compare four‐dimensional phase‐contrast magnetic resonance (4D PC‐MR), two‐dimensional (2D) PC‐MR, and transthoracic echocardiography (TTE) for quantification of AS. STUDY TYPE: Prospective. POPULATION: Twenty patients with various degrees of AS (69.3 ± 5.0 years). FIELD STRENGTH/SEQUENCES: 4D PC‐MR and 2D PC‐MR at 3T. ASSESSMENT: We compared V(peak), P(mean), and AVA between TTE, 4D PC‐MR, and 2D PC‐MR. Flow eccentricity was quantified by means of normalized flow displacement, and its influence on the accuracy of TTE measurements was investigated. STATISTICAL TESTS: Pearson's correlation, Bland–Altman analysis, paired t‐test, and intraclass correlation coefficient. RESULTS: 4D PC‐MR measured higher V(peak) (r = 0.95, mean difference + 16.4 ± 10.7%, P <0.001), and P(mean) (r = 0.92, mean difference + 14.9 ± 16.0%, P = 0.013), but a less critical AVA (r = 0.80, mean difference + 19.9 ± 20.6%, P = 0.002) than TTE. In contrast, unidirectional 2D PC‐MR substantially underestimated AS severity when compared with TTE. Differences in V(peak) between 4D PC‐MR and TTE showed to be strongly correlated with the eccentricity of the flow jet (r = 0.89, P <0.001). Use of 4D PC‐MR improved the concordance between V(peak) and AVA (from 0.68 to 0.87), and between PG(mean) and AVA (from 0.68 to 0.86). DATA CONCLUSION: 4D PC‐MR improves the concordance between the different AS parameters and could serve as an additional imaging technique next to TTE. Future studies should address the potential value of 4D PC‐MR in patients with discordant echocardiographic parameters. Level of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:472–480.