THE INFLUENCE OF FREE HAND SUTURING TECHNIQUE AND ZERO PRESSURE FIXATION ON THE HYDRODYNAMIC FUNCTION OF AORTIC ROOT AND AORTIC-VALVE LEAFLETS

Objective: There is increasing interest in the use of stentless porcin e bioprostheses implanted by the free hand suturing technique. However , preservation of the normal valve geometry and function is a matter o f concern. This study has been conducted to investigate the influence of free hand insertion on the hydrodynamic function of the aortic valv e. In particular, free sewn Valves have been compared to whole root re placements for both fresh valves and zero pressure fixed bioprostheses . Methods: Four sets of porcine aortic roots with six aortic roots in each set consisting of (A) fresh aortic roots, (B) fresh aortic valve inserted by free hand suturing technique in fresh aortic roots, (C) ao rtic valve fixed in glutaraldehyde under zero pressure, inserted by fr ee hand suturing technique in fresh aortic roots, and (D) aortic roots fixed in glutaraldehyde under zero pressure, were studied. Hydrodynam ic function and leaflet bending deformations were analysed in a modifi ed pulsatile flow simulator which incorporates the elastic aortic root s. Results: The glutaraldehyde-treated roots were found to be less dis tensible than the fresh aortic roots, with a mean dilatation of only 8 % compared with 43% for the fresh roots at 120 mmHg pressure. The othe r two groups of free sewn valves showed reasonably good dilatation of 38%. There was no significant difference between the two sets, The hyd raulic effective orifice area (EGA) of the valve, which was derived fr om the flow and pressure measurements, was divided by the actual orifi ce area for the annulus to arrive at the performance index. The perfor mance index for glutaraldehyde-fixed aortic root was the lowest, with an index of 0.47 compared with 0.91 for that of fresh roots, 0.61 for the fresh valve in fresh root and 0.50 for the glutaraldehyde-treated valve in fresh root. The mean pressure difference during the peak flow also followed the same order with 12 mmHg for the glutaraldehyde-fixe d roots: 1.8 mmHg for the fresh roots, 5.3 mmHg for the fresh valve in fresh root and 7.7 mmHg for the glutaraldehyde-treated valve in fresh root. The free hand suturing technique altered the leaflet geometry a nd caused increased open leaflet bending deformations compared to the fresh root. Both groups of free sewn valves behaved better than the ze ro pressure fixed root. Conclusions: Alteration in leaflet biomechanic s is likely to influence long-term valve durability. (C) 1997 Elsevier Science B.V.