Endoluminal graft repair for abdominal aortic aneurysms in high-risk patients and octogenarians: is it better than open repair?

OBJECTIVE

To analyze the short-term and midterm results of open and endoluminal repair of abdominal aortic aneurysms (AAA) in a large single-center series and specifically in octogenarians.

METHODS

Between January 1997 and October 2000, 470 consecutive patients underwent elective repair of AAA. Conventional open repair (COR) was performed in 210 patients and endoluminal graft (ELG) repair in 260 patients. Ninety of the patients were 80 years of age or older; of these, 38 underwent COR and 52 ELG repair.

RESULTS

Patient characteristics and risk factors were similar for both the entire series and the subgroup of patients 80 years or older. The overall complication rate was reduced by 70% or more in the ELG versus the COR groups. The postoperative death rate was similar for the COR and ELG groups in the entire series and lower (but not significantly) in the ELG 80 years or older subgroup versus the COR group. The 36-month rates of freedom from endoleaks, surgical conversion, and secondary intervention were 81%, 98.2%, and 88%, respectively.

CONCLUSION

The short-term and midterm results of AAA repair by COR or ELG are similar. The death rate associated with this new technique is low and comparable, whereas the complication rate associated with COR in all patients and those 80 years or older in particular is greater and more serious than ELG repair. Long-term results will establish the role of ELG repair of AAA, especially in elderly and high-risk patients.

Evolution of vascular fellowship training in the new era of endovascular techniques

PURPOSE

The endovascular technique has revolutionized the treatment of infrarenal abdominal aortic aneurysm (AAA). At our institution, we examined the impact of an endovascular program on the traditional operative training of the vascular fellows in the treatment of infrarenal AAA.

METHODS

We examined the records of our vascular fellows' experience from July 1995 to May 2000. We introduced the endovascular treatment for infrarenal AAA in 1995.

RESULTS

The fellows have performed increasing numbers of endovascular cases each year, with a predicted number of 124 cases for 1999-2000. However, despite an increase in the overall volume of patients with infrarenal AAA (102 cases in 1998-1999 and a predicted 160 cases in 1999-2000), the trainees will experience a reduction in the number of open AAAs from 61 cases in 1998-1999 to a predicted 36 cases in 1999-2000. However, the volume of open suprarenal AAA has also increased from eight cases in 1998 to 1999 to a predicted 24 cases in 1999-2000. With no significant change in the open aortoiliac occlusive cases from previous years, the current fellows will graduate with a similar volume of open aortic procedures as their predecessors.

CONCLUSION

With the recent advances in endovascular technology, our traditional operative approach to the treatment of AAA disease may be lacking in the training of future vascular surgeons. At our institution, although fewer open infrarenal AAA cases were performed, the trainees have maintained the open aortic experience by performing an increased volume of suprarenal AAAs. We have to critically reevaluate and redefine what constitutes adequate vascular fellow experience in the surgical treatment of abdominal aortic aneurysms.

Local irrigation with tissue factor pathway inhibitor inhibits intimal hyperplasia induced by arterial interventions

OBJECTIVE

To evaluate the capacity of local irrigation with tissue factor pathway inhibitor (TFPI) to inhibit vessels from neointimal lesion formation following intimectomy or balloon angioplasty.

DESIGN

The common carotid arteries in New Zealand white rabbits were subjected to either intimectomy or balloon angioplasty.

INTERVENTION

Before restoring blood flow, the lumina of the vessels were irrigated with 1 mL of Dulbecco phosphate-buffered saline either with TFPI (100 micrograms/mL [TFPI group, n = 10]) or without TFPI (control group, n = 10).

MAIN OUTCOME MEASURES

The area of neointimal formation and the ratio of the intimal to medial areas (I/M) were determined from elastin-stained sections.

RESULTS

The area of neointima and the I/M ratio were not significantly different at 2 weeks postoperatively. However, at 4 weeks, TFPI-treated vessels demonstrated a significant reduction in the neointimal lesion and the I/M ratio compared with those of controls, following both angioplasty and intimectomy. Transmission electron microscopy showed a lack of platelet aggregation and thrombus formation at the intimal surface in the TFPI-treated vessels.

CONCLUSIONS

Local irrigation with TFPI at the time of arterial interventional therapy inhibits intimal hyperplasia following either balloon angioplasty or intimectomy. We hypothesize that TFPI binds to the injured vessel surface and inhibits the cascade of thrombotic events that promote intimal hyperplasia.

Halofuginone, a specific collagen type I inhibitor, reduces anastomotic intimal hyperplasia

OBJECTIVE

To determine if halofuginone hydrobromide, a specific type I collagen inhibitor, could prevent intimal hyperplasia at a vascular anastomosis.

DESIGN

Intimal hyperplasia is characterized by smooth muscle cell proliferation and extracellular matrix accumulation. Halofuginone was used to block collagen production and smooth muscle cell proliferation in cell cultures and in a rabbit model of an end-to-end anastomosis of the right common carotid artery. Animals were fed a nontoxic dose of halofuginone. Eighteen rabbits were fed the inhibitor in a randomized blinded fashion and were examined after 4 weeks by harvesting the arteries after perfusion fixation at physiologic pressures.

RESULTS

Halofuginone inhibited smooth muscle cell proliferation in vitro and had no effect on cell viability. Morphometric quantification verified that halofuginone treatment significantly attenuated anastomotic intimal thickness.

CONCLUSION

Oral administration of halofuginone inhibits intimal hyperplasia at vascular anastomoses. Intimal hyperplasia inhibition by halofuginone may be a therapeutic option for preventing arterial stenosis in vascular surgery.

Vascular permeability factor accelerates endothelial regrowth following balloon angioplasty

Many failures of vascular reconstructions are due to thrombosis and restenosis and are often attributed to inadequate endothelial regeneration at the site of endothelial denudation. Vascular permeability factor (VPF) is a naturally occurring growth factor responsible for vessel permeability and microvascular angiogenesis. Here, we show that VPF stimulated rabbit endothelial cell proliferation in vitro at concentrations 100 ng/ml. However, VPF had no effect on smooth muscle cell proliferation at these concentrations up to 500 ng/ml. When VPF was administered for 4 weeks (120 micrograms, twice weekly, i.v.) following balloon angioplasty-induced endothelial denudation of rabbit carotid artery, there was a significant increase in the in vivo regeneration of endothelium compared to control (57.5 +/- 6.7% vs. 38.3 +/- 1.9%, P < 0.01). Moreover, 8 weeks of VPF administration resulted in 88.1 +/- 3.1% re-endothelialization compared to control (44.7 +/- 3.8%). Hence, VPF appears to be a specific mitogen for endothelial regeneration.

Inhibition of neointimal hyperplasia by blocking alpha V beta 3 integrin with a small peptide antagonist GpenGRGDSPCA

PURPOSE

Neointimal hyperplasia is a leading cause of restenosis after vascular procedures. Recent findings showed that smooth muscle cell (SMC) migration from the media into the neointima is a critical step in the development of the hemodynamically compromising neointimal lesion. Moreover, integrins are believed to play a role in SMC motility. Therefore we studied the role of one ubiquitous integrin, alpha V beta 3, in SMC migration.

METHODS

Transwell assay was used to study in vitro migration of human and rabbit SMCs after stimulation with platelet-derived growth factor (PDGF). A neutralizing monoclonal antibody to alpha V beta 3, LM609, and a specific arginine-glycine-aspartic acid (RGD) antagonist, GpenGRGDSPCA, were used in the migration assay to inhibit alpha V beta 3-mediated SMC migration. In addition, GpenGRGDSPCA was administered locally to rabbit carotid artery after balloon angioplasty to determine the effect of blocking alpha V beta 3 on neointimal hyperplasia.

RESULTS

We showed that PDGF-induced human SMC migration is mediated by the alpha V beta 3 integrin by use of LM609 to inhibit migration and that SMC migration is RGD dependent by use of GpenGRGDSPCA to inhibit migration. We have also inhibited rabbit SMC migration with GpenGRGDSPCA to demonstrate the cross-species preservation of the RGD peptide sequence in SMC mortality. Finally, when we administered GpenGRGDSPCA locally to rabbit carotid artery after balloon angioplasty, there was a statistically significant reduction in neointimal lesion formation compared with arteries administered an inactive peptide or saline solution.

CONCLUSIONS

We have demonstrated the important role of the alpha V beta 3 integrin in SMC migration in vitro and in neointimal hyperplasia in vivo.

Effect of endothelin-1 infusion on the development of intimal hyperplasia after balloon catheter injury

Previous studies have shown endothelin-1 (ET-1) to be mitogenic for smooth-muscle cells. We explored in vivo the ability of high ET-1 levels to worsen angioplasty restenosis. Left carotid artery balloon endothelial denudation was performed on 14 rats. ET-1 was delivered via osmotic pump at a rate of 5 pmol/kg/min. Intimal development and plasma ET-1 levels were assessed at 2 weeks. Blood pressure and heart rate were measured throughout the study. For analysis, the animals were divided into three groups based on ET-1 levels at harvest: control, 4.3 +/- 0.5 pmol/ml (n = 6); low ET-1, 5.2 +/- 0.9 pmol/ml (n = 4); and high ET-1, 23.1 +/- 5.9 pmol/ml (n = 4). Although ET-1 infusion caused blood pressure elevation in both ET-1 groups, this was more marked and prolonged in the group with a high ET-1 level at study conclusion. Evaluation of the intimal:medial area ratio showed a marked increase in intimal thickness in the high ET-1 group versus control (1.13 +/- 0.23 versus 0.35 +/- 0.11; p < 0.05). We conclude that ET-1 infusion in responsive animals can cause worsening of the intimal hyperplastic response after mechanical injury. Further study is required to elucidate whether this is entirely caused by a direct effect of ET-1 on smooth-muscle cell mitogenesis or is also by the hemodynamic effects of ET-1-induced hypertension, or an effect of another mediator released in response to the ET-1 (e.g., angiotensin II).