Long-term results justify autogenous infrainguinal bypass grafting in patients with end-stage renal failure.

INTRODUCTION: Infrainguinal bypass grafting for limb-threatening ischemia in patients with end-stage renal disease is generally thought to be associated with increased operative risk and poor long-term outcome. This retrospective study was undertaken to examine the modern-era, long-term results of infrainguinal bypass grafting in dialysis-dependent patients. METHODS: Over the past 5 years in a single institution, 425 lower extremities (368 consecutive patients) were revascularized for the indication of limb salvage. Sixty-four patients (82 limbs) were dialysis-dependent at the time of revascularization, and this group was analyzed separately. They exhibited statistically significant higher incidences of diabetes (83% vs 56%; P <.001), hypertension (91% vs 74%; P <.001), and more distal vascular disease, which required a greater proportion of proximal anastomoses at the popliteal level (24% vs 11%; P <.01) and distal anastomoses at the infrapopliteal level (75% vs 65%; P <.05). RESULTS: Despite the higher prevalence of comorbid conditions and distal disease in patients with renal failure, their perioperative 30-day mortality rate remained low (4.9%) and was not significantly different from that in patients with functioning kidneys (2.9%; P = not significant). After a median follow-up of 11 months (range, 0-60 months), the 3-year autogenous conduit secondary graft patency in patients with renal failure was no different than in patients with functioning kidneys (67% +/- 9% vs 64% +/- 5%; P = not significant). Nonautogenous conduits in dialysis-dependent patients exhibited a significantly poorer outcome with only 27% +/- 12% remaining secondarily patent at 2 years. As expected, both limb salvage and patient survival were significantly less in patients with renal faiture, although both exceeded 50% at 3 years (limb salvage 59% +/- 8% vs 68% +/- 5%; P <.05; patient survival 60% +/- 8% vs 86% +/- 4%; P <.001). The often-quoted phenomenon of limb loss, despite a patent bypass graft, occurred infrequently in this study (n = 3 of 82 limbs). CONCLUSION: Infrainguinal revascularization can be performed in dialysis-dependent patients with acceptable perioperative and long-term results, especially in patients in whom adequate autologous conduit is available.

The effects of extremely low shear stress on cellular proliferation and neointimal thickening in the failing bypass graft.

OBJECTIVE: Previous studies demonstrating a correlation between low shear stress (tau = 5-15 dyne/cm(2)) and experimental vein graft neointimal thickening (NIT) support the role of low tau in vein graft failure. However, a simple linear relationship between low tau and NIT would underestimate the degree of NIT evident in high-grade occlusive lesions of failing human vein grafts. In this study we used a new experimental model that maintains patency at low tau (< 2 dyne/cm(2)), to delineate possible deviations from linearity in the low tau --> NIT hypothesis. METHODS: Thirty-two New Zealand White rabbits underwent creation of a common carotid vein patch with a segment of ipsilateral external jugular vein. Very low tau was created in 13 patches by ligation of the distal common carotid artery, leaving the only outflow through a small muscular branch. Normal tau was created in 11 patches by leaving the common carotid artery outflow intact. High tau was created in eight patches by ligation of the contralateral common carotid artery. Six patches were harvested after 2 weeks for measurement of cell cycle entry by proliferating cell nuclear antigen (PCNA) immunohistochemistry. The remaining 26 patches were harvested after 4 weeks, perfusion fixed, and excised for morphometric analysis. RESULTS: Mean blood flow and tau at implantation ranged from 0.5 to 41 mL/min and 0.07 to 15 dyne/cm(2), respectively. At the time of harvest, 30 of 32 patches remained patent, and the artificially created aberrations in blood flow were maintained (range, 0.7-41 mL/min). After 2 weeks PCNA immunohistochemistry showed a significantly higher level of cell cycling in patches exposed to low tau (40 +/- 5 vs 1.6 +/- 0.3 PCNA-positive cells per high-power field; P <.001), which is equivalent to approximately 20% of the total cells present. In patches harvested after 4 weeks, NIT ranged from 42 to 328 microm and significantly correlated with mean tau at implantation. Patches with very low tau exhibited histologic characteristics similar to those of failing human bypass grafts, including laminar thrombus and flow-limiting luminal stenosis. The relationship between tau and NIT was nonlinear in that extremely low tau (< 2 dyne/cm(2)) resulted in NIT beyond that predicted by a simple linear correlation (P =.003). CONCLUSION: Extremely low tau (< 2 dyne/cm(2)) stimulates high rates of smooth muscle cellular proliferation in arterialized vein patches. NIT is accelerated in these regions of low tau far beyond that predicted by a simple linear model. The nonlinear nature of the cellular proliferative response and NIT at tau less than 2 dyne/cm(2) may explain the rapid progression of neointimal lesions in failing bypass grafts.

The hemodynamics of vein grafts: measurement and meaning.

The long-term patency of infrainguinal vein grafts appears to depend primarily on the size and quality of the venous conduit. Therefore, those quantities which directly relate to the conduit's ability to act as a transporter of blood, namely internal diameter and longitudinal impedance (Z(L)), have predictive value for patency. Autologous grafts of good quality frequently remain patent even with compromised outflow. Therefore, those quantities that are outflow dependent, including deltaP, flow, velocity, shear stress, and resistance, carry less predictive value for long-term performance.

Prevention of restenosis by a herpes simplex virus mutant capable of controlled long-term expression in vascular tissue in vivo.

Neointimal hyperplasia resulting from vascular smooth muscle cell (SMC) proliferation and luminal migration is the major cause of autologous vein graft failure following vascular coronary or peripheral bypass surgery. Strategies to attenuate SMC proliferation by the delivery of oligonucleotides or genes controlling cell division rely on the use of high concentrations of vectors, and require pre-emptive disruption of the endothelial cell layer. We report a genetically engineered herpes simplex virus (HSV-1) mutant that, in an in vivo rabbit model system, infects all vascular layers without prior injury to the endothelium; expresses a reporter gene driven by a viral promoter with high efficiency for at least 4 weeks; exhibits no systemic toxicity; can be eliminated at will by administration of the antiviral drug acyclovir; and significantly reduces SMC proliferation and restenosis in vein grafts in immunocompetent hosts.

Hemodialysis access: influence of the human immunodeficiency virus on patency and infection rates.

PURPOSE: The complication rate for patients who are dialysis dependent and infected with the human immunodeficiency virus (HIV) and the role of viral indicators (CD4 counts) as predictors of these complications are poorly characterized. To determine the influence of HIV status and viral activity on graft patency and infection rates, we retrospectively reviewed our results. METHODS: Between June 1993 and March 1997, the charts of 104 patients (HIV+, n = 42; HIV-, n = 62) who required 112 hemodialysis access grafts were reviewed. Of the 112 procedures, 55 (48%) were autologous arteriovenous fistulae (AVF) procedures (HIV+, n = 23; HIV-, n = 32) and 57 (52%) were prosthetic expanded polytetrafluoroethylene grafting procedures (HIV+, n = 27; HIV-, n = 30). Transcutaneous catheter procedures were excluded from the study. The autologous AVF procedures consisted of direct and transposed AVFs. Patency rates were determined by means of life-table analysis. Infection rates and CD4 counts were compared with the chi2 test and the Fisher exact test. Significance was accepted at a P value of.05 or less. RESULTS: The cumulative 12-month and 24-month patency rates for prosthetic grafts in patients who were HIV+ were 49% and 21%, respectively, versus 77% and 45% for patients who were HIV-. The differences in the prosthetic graft patency rates between these two groups were significant (P .05). The mean CD4+ cell counts were 174: CD4+ counts that were less than 200 did not correlate with or predict the development of infection (P >.05). CONCLUSION: Our data showed that prosthetic graft infection rates were increased and patency rates were decreased in patients who were HIV+ as compared with patients who were HIV- and HIV+ with autologous AVFs. There were no differences in patency rates or infection rates in patients who had undergone autologous access procedures. Long-term graft patency rates were not affected by HIV status, and CD4+ lymphocyte counts were not predictive of infection development. Because the prosthetic graft infection rates exceeded those rates of autologous access procedures, we recommend the vigorous use of autologous AVFs in all patients who are HIV+, regardless of CD4+ count.