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European Journal of Cardio-Thoracic Surgery, Vol 11, 280-286, Copyright © 1997 by European Association for Cardio-thoracic Surgery
P Revanna, J Fisher and KG Watterson
OBJECTIVE: There is increasing interest in the use of stentless porcine
bioprostheses implanted by the free hand suturing technique. However,
preservation of the normal valve geometry and function is a matter of
concern. This study has been conducted to investigate the influence of free
hand insertion on the hydrodynamic function of the aortic valve. In
particular, free sewn valves have been compared to whole root replacements
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 valve fixed in glutaraldehyde under zero
pressure, inserted by free hand suturing technique in fresh aortic roots,
and (D) aortic roots fixed in glutaraldehyde under zero pressure, were
studied. Hydrodynamic function and leaflet bending deformations were
analysed in a modified pulsatile flow simulator which incorporates the
elastic aortic roots. RESULTS: The glutaraldehyde-treated roots were found
to be less distensible than the fresh aortic roots, with a mean dilatation
of only 8% compared with 43% for the fresh roots at 120 mmHg pressure. The
other two groups of free sewn valves showed reasonably good dilatation of
38%. There was no significant difference between the two sets. The
hydraulic effective orifice area (EOA) of the valve, which was derived from
the flow and pressure measurements, was divided by the actual orifice area
for the annulus to arrive at the performance index. The performance 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 associated the same
order with 12 mmHg for the glutaraldehyde-fixed 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 and caused increased open leaflet
bending deformations compared to the fresh root. Both groups of free sewn
valves behaved better than the zero pressure fixed root. CONCLUSIONS:
Alteration in leaflet biomechanics is likely to influence long-term valve
durability.
ARTICLES
The influence of free hand suturing technique and zero pressure fixation on the hydrodynamic function of aortic root and aortic valve leaflets
Killingbeck Hospital, University of Leeds, UK.
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