Comprehensive analysis of haemodynamics in patients with physiologically curved prostheses of the ascending aorta

OBJECTIVES This is a comprehensive analysis of haemodynamics after valve-sparing aortic root replacement (VSARR) with anatomically curved prosthesis (CP) compared to straight prosthesis (SP) and age-matched volunteers (VOL) using 4D flow MRI (time-resolved three-dimensional magnetic resonance phase-contrast imaging). METHODS Nine patients with 90 degrees CP, nine patients with SP, and twelve VOL were examined with 4D flow MRI. Analyses included various characteristic anatomical, qualitative and quantitative haemodynamic parameters. RESULTS Grading of secondary flow patterns was lower in CP patients than in SP patients (P = 0.09) and more comparable to VOL, albeit not reaching statistical significance. However, it was easy to differentiate between VSARR patients and healthy volunteers: Patients more often had angular aortic arches (CP: 89%, SP: 100%; VOL: 17%; P <= 0.002), increased average curvature (CP: 0.17/cm [0.15, 0.18]; SP: 0.15/cm [0.14, 0.16]; VOL: 0.14/cm [0.13, 0.16]; P <= 0.007; values given as median [interquartile range]), and more secondary flow patterns (CP: 3 [2, 4] SP: 3 [2, 3] VOL: 2 [1, 2]; P < 0.01). Maximum circulation (CP: 142.7 cm(2)/s [116.1, 187.3]; SP: 101.8 cm(2)/s [77.7, 132.5]; VOL: 42.8cm(2)/s [39.3, 65.6]; P <= 0.002), maximum helicity density (CP: 9.6 m/s(2) [9.3, 23.9]; SP: 9.7 m/s(2) [8.6, 12.5]; VOL 4.9 m/s(2) [4.2, 7.7]; P <= 0.007), and wall shear stress gradient (e.g., proximal ascending aorta CP: 0.97 N/m(2) [0.54, 1.07]; SP: 1.08 N/m(2) [0.74, 1.24]; VOL: 0.41 N/m(2) [0.32, 0.60]; P <= 0.01) were increased in patients. One CP patient had a round aortic arch with physiological haemodynamic parameters. CONCLUSIONS The restoration of physiological aortic configuration and haemodynamics was not fully achieved with the curved prostheses in our study cohort. However, there was a tendency towards improved haemodynamic conditions in the patients with curved prostheses overall but without statistical significance. A single patient with a CP and near-physiological configuration of the thoracic aorta underlines the importance of optimizing postoperative geometric conditions for allowing for physiological haemodynamics and cardiovascular energetics after VSARR.