Influence of Aortic Dilation on the Regional Aortic Stiffness of Bicuspid Aortic Valve Assessed by 4-Dimensional Flow Cardiac Magnetic Resonance: Comparison With Marfan Syndrome and Degenerative Aortic Aneurysm

Abstract

Objectives: This study sought to ascertain whether patients with a bicuspid aortic valve (BAV) have an intrinsic alteration in regional aortic stiffness compared with patients with tricuspid aortic valve (TAV) and Marfan syndrome (MFS) patients with similar aortic sizes, as well as to assess the influence of ascending aorta (AAo) dilation on regional stiffness parameters in BAV patients.

Background: Imaging biomarkers as predictors of BAV, MFS, and degenerative AAo aneurysms in TAV patients (DA-TAV) are lacking. Biomechanical characterization has been proposed as a possible tool for further aneurysm stratification.

Methods: A total 234 subjects (136 BAV, 44 MFS, and 18 DA-TAV patients and 36 healthy control subjects) were included. The cardiac magnetic resonance protocol comprised 4-dimensional flow to assess AAo and descending aorta (DAo) pulse wave velocities (PWVs) and double-oblique, 2-dimensional, steady-state free-precession cine cardiac magnetic resonance to compute aortic distensibility (AD).

Results: On adjusted analysis, nondilated BAV patients had similar PWV and AD as healthy control subjects in both AAo and DAo, whereas dilated BAV did not differ from DA-TAV. In contrast, AAo and DAo stiffness in MFS patients was markedly greater than in BAV patients, increasing slightly with dilation severity. AAo PWV showed a biphasic pattern in BAV patients: it first decreased and then increased throughout AAo dilation, with a clear turning point at 50 mm, whereas distensibility did not discern mildly dilated aorta. In multivariate analysis adjusted for clinical and demographic characteristics, only PWV was related to AAo dilation in BAV patients.

Conclusions: The mechanical properties of AAo aneurysms are similar in BAV and TAV patients, whereas MFS patients have a stiffer aorta. Aortic stiffness strongly depends on dilation severity. AAo PWV resulted in a potentially clinically useful biphasic trend with respect to aneurysm diameter, whereas distensibility did not discern mildly dilated aorta. Beyond clinical risk factors, PWV but not AD was independently related to AAo dilation in BAV patients.

Keywords: 4D flow CMR; Marfan syndrome; ascending aorta aneurysm; bicuspid aortic valve; distensibility; pulse wave velocity.