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Eur J Cardiothorac Surg 1999;15:294-301
© 1999 Elsevier Science NL
a Yorkshire Heart Centre, Leeds General Infirmary, Calverley Street, Leeds LS1 3EX, UK
b School of Mechanical Engineering, University of Leeds, Leeds, UK
Received 22 September 1998; received in revised form 21 December 1998; accepted 8 January 1999.
Corresponding author. Tel.: +44-113-392-5738; fax: +44-113-392-5865; e-mail: kevingw@ulth.northy.nhs.uk
Objectives: We established an in vitro model to investigate the effect of size mismatch between the aortic and pulmonary root on the hydrodynamic performance and leaflet motion of the pulmonary autograft. Methods: Ten fresh porcine pulmonary roots (annulus diameter: 19–25 mm) were tested in a pulsatile flow simulator. The autografts then were implanted in fresh porcine aortic roots (annulus diameter: 19–30 mm) and retested in the flow simulator. Three roots were oversized by 21–39%, three were undersized by 32–45% and there were four size for size implantations. The external diameter of the roots and autografts was measured at the sinotubular junction at hydrostatic pressures of 0–120 mmHg. The transvalvular gradient and regurgitation were also measured and the effective orifice area was calculated. The leaflet motion was recorded on video. Results: The fresh pulmonary roots were more compliant than the fresh aortic roots (46±8.4% vs. 35±7.8% dilatation from 0 to 120 mmHg). The group of matching size autografts dilated by 43±4.9% in the same pressure range. The external diameter of the undersized autografts was 10±2.1% bigger than before implantation at 0 pressure and then the dilatation was 40±5.3% at 120 mmHg. The oversized implantation made the autografts 11±9.4% smaller in their relaxed state, but then they dilated by 65±11% as the pressure increased to 120 mmHg, resulting in a net dilatation of 54% over the original undilated state. The under or oversizing had little effect on the pressure gradient measured across the valves (5.6±2.57 mmHg before, 6.3±3.27 mmHg after implantation). Only the oversized valves showed significantly higher gradients than the native pulmonary valves. The effective orifice area of the undersized autografts was slightly bigger and the oversized autografts was slightly smaller after implantation, although the differences were not significant. The size mismatch did not cause regurgitation on the valves. The video images showed very low-open leaflet-bending deformation, both on the fresh pulmonary and the autograft valves. Conclusion: Under or oversizing the pulmonary autograft up to 40% of the annulus diameter did not affect the hydrodynamic parameters significantly. The compliance of the autograft root was able to compensate for the size mismatch without adversely influencing the valve performance.
Key Words: Pulmonary autograft • Size mismatch • Hydrodynamic parameters • Leaflet motion
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