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The influence of sizing on the dynamic function of the free-hand implanted porcine aortic homograft: an in vitro study.

BACKGROUND AND AIMS OF THE STUDY
The influence of sizing on the function of a porcine aortic valve after its implantation using the free-hand technique in the subcoronary position was investigated.


METHODS
Dynamic function and leaflet configuration of the valve (n = 16) were first analyzed in its natural aortic root in a left heart simulator at 120/80 mmHg pressure and 4 l/min cardiac output. The valve was then implanted in the recipient porcine aortic root and re-studied. Three groups were investigated: group I (n = 4) comprised of 1-2 mm smaller donor aortic valve than the recipient; group II (n = 8) 3-4 mm smaller; and group III (n = 4) 5-7 mm smaller. Orifice area (OA), systolic and diastolic configurations of the leaflets, pattern and timing of leaflet opening and closure, commissural movement, pressure gradient and valvular regurgitation were analyzed.


RESULTS
In the intact donor aortic root, average expansion of the aorta at the commissures, for a pressure change from 0 to 80 mmHg, was about 42%. This was reduced significantly in all assemblies. Group I showed a 34% reduction in OA, and excessive leaflet bending; there was no aortic insufficiency (AI) or pressure gradient across the valve. In group III there was a lesser reduction in OA and reduced leaflet bending, but two of four valves had AI. In group II, the reduction in OA was only 13%, there was less leaflet bending, and no AI.


CONCLUSIONS
The donor valve 3-4 mm smaller than the recipient seems an optimal match. The current practice of using the same size donor as recipient may be responsible for excessive leaflet bending and may be implicated in early deterioration of the homograft.