078 A randomised study of the effects of bi-leaflet prosthesis orientation on aortic haemodynamics and coronary flow velocity profiles

Objectives The orientation of curved bi-leaflet mechanical prosthesis has been shown to significantly affect the development of aortic sinus flow in the in vitro study. However, its clinical implication for trans-aortic pressure gradient or coronary flow dynamics remains to be defined. The present study was aimed to characterise these two haemodynamic aspects by randomising the orientation of MIRA aortic prosthesis in patients undergoing aortic valve replacement (AVR). Methods 45 patients (58±12 years, 36 males) undergoing AVR with a MIRA prostheses were randomised to anatomic (leaflets parallel to left coronary) or anti-anatomic (leaflets perpendicular to left coronary) orientation. Echocardiography was performed at 1 week and 12 months after AVR to assess prosthesis pressure gradient, LV mass and LAD flow velocity profiles. Results Aortic prosthesis and coronary LAD haemodynamics were analysed with respect to follow-up time and orientation by twoway ANOVA. In valve size >23 mm, prosthesis orientation did not affect valve haemodynamics, LAD flow profiles or LV mass index (all p>0.05). In valve size ≤23 mm, anti-anatomic orientation group had higher mean prosthesis pressure gradient (8.1±0.5 vs 6.3±0.5, mm Hg, p=0.023), but also a greater LAD systolic flow velocity (17.5±1.1 vs 13.8±1.4, cm/s, p=0.048) and longer LAD systolic flow duration (235±7 vs 208±9, ms, p=0.030) than those of anatomic orientation. LAD diastolic flow velocity and LV mass index did not differ between the two orientations (p>0.05). Conclusions Anti-anatomic orientation of MIRA aortic prosthesis appears to produce more physiological LAD systolic flow profiles, which can be explained by a stronger aortic sinus vortices flow demonstrated by previous in vitro study. A greater pressure gradient in the same orientation, however, suggests the possibility of fluid dynamics across its central orifice may be insulated by the vortices flow in aortic sinus, implying a complex 3D velocity profile produced by the curved bi-leaflets prosthesis.