The work reported in this thesis is an inherent part of research
carried out in Edinburgh to assess the performance and durability of heart
valve prostheses. Frcm 1975 to 1979 540 patients undergoing heart valve
replacement in Edinburgh Royal Infirmary were entered into a randomised
trial and received either a mechanical (Bjork-Shiley), or porcine
heterograft (Hancock or Carpentier-Edwards) prosthesis. Starting in 1977
in the United States the Veterans Administration carried out a similar
randomised trial on 575 patients. After a mean period of 5 years no
significant advantage to any of the three prostheses was observed,
although there were some differences in the results reported in the
Edinburgh and the US trials and possible explanations for these are
proposed.This thesis extends the analysis of the trial to a mean period of
10.5 years with respect to survival, and the incidence of reoperation,
complications of anticoagulation, systemic embolism and bacterial
endocarditis. It also presents a Doppler ultrasound comparison of the
haemodynamic performance of the different valves in a subset of 102
patients.After this extended follow-up period we have again observed no
difference in survival between those receiving a mechanical or porcine
prosthesis. Reoperation for valve failure was necessary significantly
more often in patients with porcine prostheses (53 patients) than in those
with the Bjork-Shiley prosthesis (17 patients). This difference was
almost entirely due to cusp failure of porcine prostheses occurring more
than 5 years after implantation. An actuarial analysis of valve survival
using reoperation or cardiac death as end-points showed significantly
better valve survival for patients receiving the Bjork-Shiley prosthesis
when all patients and the subgroup undergoing mitral valve replacement
were considered, but not in the subgroup receiving an aortic valve
replacement.All patients with Bjork-Shiley prostheses received longterm
anticoagulation therapy, and bleeding complications were more frequent in
this group. Death, reoperation, bleeding and complications of
anticoagulation, .systemic embolism and bacterial endocarditis were taken
as end points for an actuarial analysis of "event-free survival". There
was a non-significant trend in favour of the Bjork-Shiley prosthesis when
all patients and the subgroup undergoing mitral valve replacement were
considered, but no discemable trend after aortic valve replacement.Doppler ultrasound techniques have been used to compare the
haemodynamic performance of the Bjork-Shiley and porcine prostheses an
average of 10 years after implantation in 102 patients enrolled in the
Edinburgh trial. No significant difference in peak instantaneous or mean
pressure gradient across the prosthesis was observed in patients who had
undergone aortic or mitral valve replacement. There was however a
significantly lower pressure half-time in patients with Bjork-Shiley
compared with those with porcine mitral valve prostheses but this fell
after exercise in those with porcine mitral prostheses, suggesting that
this difference, observed at rest does not indicate better haemodynamic
performance of the Bjork-Shiley prosthesis
