Impact of valve-sparing aortic root replacement on aortic fluid dynamics and biomechanics in patients with syndromic heritable thoracic aortic disease.

Background: Patients with syndromic heritable thoracic aortic diseases (sHTAD) who underwent prophylactic aortic root replacement are at high risk of distal aortic events, but the underlying mechanisms remain unclear. This prospective, longitudinal study evaluates the impact of valve-sparing aortic root replacement (VSARR) on aortic fluid dynamics and biomechanics in these patients.

Methods: Sixteen patients with Marfan or Loeys-Dietz syndrome underwent two time-resolved three-dimensional phase-contrast cardiovascular magnetic resonance (4D flow CMR) studies before (sHTAD-preSx) and after VSARR (sHTAD-postSx). Two matched cohorts of 40 healthy volunteers (HV) and 16 sHTAD patients without indication for aortic root replacement (sHTAD-NSx) with available 4D flow CMR were included for comparison. In-plane rotational flow (IRF), systolic flow reversal ratio (SFRR), wall shear stress (WSS), pulse wave velocity (PWV), and aortic strain were analyzed in the ascending (AscAo) and descending aorta (DescAo).

Results: All patients with sHTAD presented altered hemodynamics and increased stiffness (p < 0.05) compared to HV, both in the AscAo (median PWV 7.4 in sHTAD-NSx; 6.8 in sHTAD-preSx; 4.9 m/s in HV) and DescAo (median PWV 9.1 in sHTAD-NSx; 8.1 in sHTAD-preSx; 6.3 m/s in HV). Patients awaiting VSARR had markedly reduced in-plane (median IRF -2.2 vs 10.4 cm²/s in HV, p = 0.001), but increased through-plane flow rotation (median SFRR 7.8 vs 3.8% in HV, p = 0.002), and decreased WSS (0.36 vs 0.47 N/m² in HV, p = 0.004) in the proximal DescAo. After VSARR, proximal DescAo IRF (p = 0.010) and circumferential WSS increased (p = 0.011), no longer differing from HV, but SFRR, axial WSS and stiffness remained altered. Patients in which aortic tortuosity was reduced after surgery showed greater post-surgical increase in IRF compared to those in which tortuosity increased (median IRF increase 18.1 vs 3.3 cm²/s, p = 0.047). Most AscAo flow alterations were restored to physiological values after VSARR.

Conclusion: In patients with sHTAD, VSARR partially restores downstream fluid dynamics to physiological levels. However, some flow disturbances and increased stiffness persist in the proximal DescAo. Further longitudinal studies are needed to evaluate whether persistent alterations contribute to post-surgical risk.