Global Aortic Pulse Wave Velocity is Unchanged in Bicuspid Aortopathy With Normal Valve Function but Elevated in Patients With Aortic Valve Stenosis: Insights From a 4D Flow MRI Study of 597 Subjects

Background: Aortopathy is common with bicuspid aortic valve (BAV), and underlying intrinsic tissue abnormalities are believed causative. Valve-mediated hemodynamics are altered in BAV and may contribute to aortopathy and its progression. The contribution of intrinsic tissue defects versus altered hemodynamics to aortopathy progression is not known. Purpose: To investigate relative contributions of tissue-innate versus hemodynamics in progression of BAV aortopathy. Study Type: Retrospective. Subjects: Four hundred seventy-three patients with aortic dilatation (diameter ≥40 mm; comprised of 281 BAV with varied AS severity, 192 tricuspid aortic valve [TAV] without AS) and 124 healthy controls. Subjects were 19–91 years (141/24% female). Field Strength/Sequence: 1.5T, 3T; time-resolved gradient-echo 3D phase-contrast (4D flow) MRI. Assessment: A surrogate measure for global aortic wall stiffness, pulse wave velocity (PWV), was quantified from MRI by standardized, automated technique based on through-plane flow cross-correlation maximization. Comparisons were made between BAV patients with aortic dilatation and varying aortic valve stenosis (AS) severity and healthy subjects and aortopathy patients with normal TAV. Statistical Tests: Multivariable regression, analysis of covariance (ANCOVA), Tukey's, student's (t), Mann–Whitney (U) tests, were used with significance levels P < 0.05 or P < 0.01 for post-hoc Bonferroni-corrected t/U tests. Bland–Altman and ICC calculations were performed. Results: Multivariable regression showed age with the most significant association for increased PWV in all groups (increase 0.073–0.156 m/sec/year, R² = 0.30–48). No significant differences in aortic PWV were observed between groups without AS (P = 0.20–0.99), nor were associations between PWV and regurgitation or Sievers type observed (P = 0.60, 0.31 respectively). In contrast, BAV AS patients demonstrated elevated PWV and a significant relationship for AS severity with increased PWV (covariate: age, R² = 0.48). BAV and TAV patients showed no association between aortic diameter and PWV (P = 0.73). Data Conclusion: No significant PWV differences were observed between BAV patients with normal valve function and control groups. However, AS severity and age in BAV patients were directly associated with PWV increases. Evidence Level: 3. Technical Efficacy: Stage 3.