Clinical implications
The success of CABG is dependent on long-term graft patency because vein
graft occlusion is associated with a return of cardiac symptoms, an
increase in myocardial infarction and death.[5, 26] Aspirin therapy
reduces early vein graft thrombosis, but no treatment, with the
exception of aggressive lipid lowering has been shown to attenuate the
incidence of vein graft atherosclerosis and improve long-term graft
patency.[4, 5, 27] The E2F antisense oligonucleotide, Edifoligide,
reduced neointima formation in pre-clinical experiments, showed clinical
efficacy in a first in human study, but failed to benefit graft patency
in a phase 2 study.[28] A method for external vein graft stenting
also reduced wall thickness in pigs, but proved impractical in
patients.[24, 29] These failures prompted us to re-evaluate simple
surgical techniques for vein graft harvesting that might improve
patency. Such interventions do not increase operative costs and require
no laboratory or manufacturing resources.
Souza, in a RCT with veins harvested using the pedicled technique
reported a superior patency compared to veins harvested conventionally
(90% versus 76% at a mean of 8.5 years post-grafting, p=0.01).[30]
Assessment of a subset of vein grafts using IVUS (18 patients) showed
less intimal hyperplasia and atherogenesis in grafts harvested with the
surrounding pedicle (mean intimal thickness 0.42±0.07mm versus
0.53±0.08mm, p<0.01).[16] Similar excellent long-term
results were reported by this group in a comparison of pedicled vein
grafts with radial artery grafts.[22] Although the improved graft
patency with the pedicled technique is encouraging the results derive
from a single surgeon study and have not been confirmed by others.
Compared to low pressure distention of conventionally harvested veins,
pedicle grafting requires more extensive dissection (which led to a
number of protocol deviations) and increases the frequency of leg wound
morbidity.[11] Our data demonstrate that it is possible to achieve
similar benefits in terms of reduced wall thickening to pedicled grafts
by using low pressure distension of conventionally harvested veins.
Strengths and
limitations
Strengths include the inclusive
eligibility criteria, with few patients being ineligible and
minimisation of bias through concealed allocation. Personnel conducting
the analyses, participants and staff not involved in the surgical
procedure were blinded to the group allocation. The factorial study
design allows two interventions to be evaluated in one study.
Limitations include that participants were recruited from a single
centre, limiting the generalizability of the findings. There were
protocol deviations, mostly in the pedicle harvest group, which reduces
the power of the study to detect differences between the interventions.
Some patients withdrew and did not attend the follow-up at 12 months,
although the impact of this missing data was minimised by estimating the
missing data using multiple imputation.
In conclusion, conventional saphenous vein graft preparation with
low pressure distension and harvesting the vein with a surrounding
pedicle yielded similar graft wall thickness after 12 months, but low
pressure distention was associated with fewer short and long-term
adverse events.
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