Early biomechanical changes in lower extremity vein grafts—distinct temporal phases of remodeling and wall stiffness
Presented at the Thirty-second Annual Meeting of The New England Society for Vascular Surgery, Stowe, VT, September 18, 2005.
Received 15 February 2006; accepted 6 June 2006. published online 23 August 2006.
Background
The geometric and biomechanical changes that contribute to vein graft remodeling are not well established. We sought to measure patterns of adaptation in lower extremity vein grafts and assess their correlation with clinical outcomes.
Methods
We conducted a prospective, longitudinal study of patients undergoing infrainguinal reconstruction with autogenous conduit. In addition to standard duplex surveillance, lumen diameter (of a defined index segment of the conduit) and pulse wave velocity (PWV) were assessed by ultrasound imaging at surgery and at 1, 3, and 6 months postoperatively. Graft dimensions and wall stiffness were correlated with clinical outcomes.
Results
There were 92 patients and 96 limbs in this study. On average, vein graft lumen diameter increased during the first month of implantation from 0.37 ± .01 cm to 0.45 ± 0.02 cm (mean ± SEM; P = .002), representing a relative change of +21.6% (median ± 14%; range, −31 to +67%) during this period. Of the entire cohort, 72% of grafts demonstrated appreciable dilation of the index segment during the first month. Index segment lumen diameter did not change appreciably beyond 1 month, with the notable exception of arm vein conduits, which showed continued tendency to dilate. PWV increased during the first 6 months (17.2 ± 1.2 m/s to 23.2 ± 2.4 m/s; P = .008), reflecting a nearly 40% increase in conduit stiffness (2.0 ± .6 Mdynes/cm to 3.3 ± .8 Mdynes/cm, P = .01). The greatest relative increase (25%) in PWV occurred from months 1 to 3. Loss of primary patency occurred in 24 cases (19 revisions, 5 occlusions), with a mean reintervention time of 7.6 months. Grafts that demonstrated early positive remodeling (lumen dilatation) had a trend of increased primary patency (P = .08, log rank). Among the grafts that failed, a trend was noted toward greater wall stiffness at 1 month, 2.7 vs 1.5 Mdynes (P = .08).
Conclusion
Vein graft remodeling appears to involve at least two distinct temporal phases. Outward remodeling of the lumen occurs early, and wall stiffness changes occur in a more delayed fashion. Early outward remodeling may be important for successful vein graft adaptation.
Brigham and Women’s Hospital, Harvard Medical School, Boston, Mass.
Correspondence: Michael S. Conte, MD, Associate Professor of Surgery, Harvard Medical School, Brigham and Women’s Hospital, Division of Vascular Surgery, 75 Francis St, Boston, MA 02115.
Supported by funding from the National Heart, Lung, and Blood Institute (HL75771 to M. A. C. and M. S. C.), and by the Clinical Investigator Training Program in Health, Science, and Technology, Harvard Medical School and Massachusetts Institute of Technology (C. D. O.).
ABSTRACT