Scott L. Stevens

Covered stents for injuries of subclavian and axillary arteries.

INTRODUCTIONnInjury to the subclavian and axillary arteries is uncommon. Exposure of these vessels is associated with significant morbidity, and mortality ranges from 5% to 30%. Endovascular methods may offer an alternative approach to these technically challenging injuries.nnnMETHODSnWe retrospectively studied patients with blunt or penetrating (including iatrogenic) injuries to the subclavian or axillary artery between January 1, 1996 and July 30, 2002. Demographic data, mechanism of injury, concomitant injuries, angiographic findings, and treatment method and outcome were recorded.nnnRESULTSnTwenty-seven patients with injury to the subclavian or axillary artery were seen at our institution during the study. Twenty-three patients underwent interventions. Eleven patients required open repair; 12 patients had lesions amenable to endovascular repair. Depending on the preference of the surgeon, 5 patients with injuries amenable to endovascular repair underwent open repair, and 7 underwent endovascular repair. A Wallgraft endoprosthesis was used in all patients; two grafts were required in 1 patient. Endovascular repair was associated with shorter operative time (P =.04) and less blood loss (P =.01). One-year patency was similar between the two groups.nnnCONCLUSIONnCovered stents are a feasible alternative to open repair in properly selected patients with subclavian or axillary artery injury, resulting in shorter procedure time and less blood loss.

Vascular endothelial growth factor and heparin in a biologic glue promotes human aortic endothelial cell proliferation with aortic smooth muscle cell inhibition.

BACKGROUNDnIncomplete luminal endothelialization may contribute to small diameter vascular graft failure. Vascular endothelial growth factor (VEGF) can be used to stimulate endothelialization without provoking smooth muscle cell (SMC) proliferation. Heparin and VEGF in a fibrin glue (FG) were investigated for their ability to promote selective human aortic endothelial cell (HAEC) proliferation and human aortic smooth muscle cell (HASMC) inhibition.nnnMETHODSnHAECs and HASMCs were seeded on FG containing VEGF (2.5, 10, 30, 100 ng/ml) or VEGF and heparin (5, 50, 500 units/ml). Proliferation assays were performed with tritiated thymidine on days 1 and 3. Results were analyzed by ANOVA, with p < or = 0.05 significant.nnnRESULTSnHAEC proliferation on FG with 10, 30, and 100 ng/ml VEGF was significantly greater than FG alone at days 1 and 3. The addition of 50 units/ml heparin to VEGF significantly increased HAEC proliferation to greater than FG with VEGF alone at day 1. Human aortic SMC proliferation was not stimulated by the addition of VEGF. The addition of 5, 50, and 500 units/ml heparin significantly inhibited HASMC proliferation regardless of VEGF concentration.nnnDISCUSSIONnVEGF at 10 ng/ml combined with heparin at 50 units/ml exhibited maximal stimulation of HAECs with inhibition of HASMCs. VEGF and heparin in a biologic glue may improve patency by selectively promoting HAEC proliferation without HASMC growth on synthetic vascular bypass grafts.

Regulation of vascular smooth muscle cell expression and function of matrix metalloproteinases is mediated by estrogen and progesterone exposure

OBJECTIVEnPostmenopausal women receiving hormone replacement therapy (HRT) have been reported to have more adverse outcomes after vascular reconstructions, including increased intimal hyperplasia development and bypass graft failure. HRT may be affecting the pathway contributing to intimal hyperplasia. An important component of this pathway involves matrix metalloproteinases (MMPs), implicated in vascular remodeling due to their ability to degrade components of the extracellular matrix. We hypothesize that estrogen (Est) and progesterone (Prog) upregulate the MMP pathway in vascular smooth muscle cells (VSMCs) thereby increasing MMP activity and function.nnnMETHODS AND RESULTSnVSMCs were incubated with Est (5 ng/mL), Prog (50 ng/mL), Est + Prog combination (Est/Prog), and/or doxycycline (40 microg/mL; Doxy). Using reverse transcriptase polymerase chain reaction (RT-PCR) analysis we have previously shown membrane type 1-MMP (MT1-MMP) messenger ribonucleic acid (mRNA) levels are significantly increased by Est. Here, Western blot analyses indicated MT1-MMP and MMP-2 protein levels, not tissue inhibitor of MMP-2 (TIMP-2), were increased in response to Est and Est/Prog (P < .05 vs control). In-gel zymography revealed that Est and Est/Prog resulted in increased MMP-2 activity (hormone groups, P < .05 vs control) with no significant difference among the hormone groups. VSMC migration was increased by 45 +/- 14% in response to Est (P < .05 vs control), as measured using a modified Boyden chamber assay. Doxycycline significantly inhibited basal and Est/Prog-stimulated increases in MMP-2 activity (P < .05 vs control; P < .05 vs hormone groups), and partially blocked basal and hormonally stimulated migration (P < .05 vs control and Est).nnnCONCLUSIONnEstrogen and progesterone affects the MMP pathway by increasing MMP-2 enzymatic activity, possibly via the upregulation of MT1-MMP expression without a corresponding increase in TIMP expression. This increased collagenase activity increases VSMC motility and their ability to migrate through a collagen type IV lattice. Est/Prog upregulation of MT1-MMP may contribute to the adverse effect of HRT on vascular interventions.

Effect of Hormones on Matrix Metalloproteinases Gene Regulation in Human Aortic Smooth Muscle Cells

BACKGROUNDnPostmenopausal women receiving hormone replacement therapy have more adverse outcomes after vascular reconstructions. Estrogen-binding receptors have been identified on vascular smooth muscle cells (VSMCs), indicating that vascular function may be under direct hormonal control. A key group of enzymes involved in vascular remodeling are matrix metalloproteinases (MMPs). Here we studied the effect of estrogen (Est) and progesterone (Prog) on MMP gene expression in human VSMCs.nnnMETHODS AND RESULTSnVSMCs were incubated with Est (5 ng/mL), Prog (50 ng/mL), Est+Prog combination (Est/Prog), and interleukin-1beta (100 U/mL; IL-1beta). Gene array analysis indicated Est+IL-1beta increased the expression of MMP-3. Reverse transcriptase-polymer chain reaction (RT-PCR) analyses revealed MMP-3 mRNA levels were significantly increased by Est/Prog+IL-1beta treatment. However, Western blot and further RT-PCR analyses indicated no change in MMP-3 in response to hormones alone. RT-PCR analyses revealed membrane type 1 (MT1)-MMP mRNA levels, not MMP-2 or tissue inhibitor of MMP (TIMP), were significantly increased by Est/Prog+IL-1beta, and Western blot analyses confirmed a significant increase in MT1-MMP protein in response to Est alone.nnnCONCLUSIONnEstrogen and progesterone affect the MMP pathway of VSMCs via isoform specific mechanisms and may lead to unbalanced MMP regulation. Estrogen up-regulates MT1-MMP without a corresponding increase in TIMP-2, known activator and inhibitor of MMP-2, respectively. Additionally, estrogen up-regulates MMP-3 only in the presence of IL-1beta. This differential regulation, combined with case-specific variations in degree of inflammatory response, may explain why some women receiving exogenous hormone therapy at the time of vascular interventions are more susceptible to complications.

Topical application of β-radiation to reduce intimal hyperplasia after carotid artery balloon injury in rabbit: A possible application for brachytherapy in vascular surgery

PURPOSEnEndovascular brachytherapy for the prevention of intimal hyperplasia (IH) and restenosis after balloon/stent angioplasty has proven effective both in animal preparations and clinical trials. A variety of beta-emitting isotopes and catheter-based devices have been developed for the delivery of low-dose radiation in clinical coronary and peripheral trials. No platform, however, has yet been developed for brachytherapy in concert with vascular surgical operations. The purpose of this study was to evaluate the vascular histopathologic response following balloon injury to rabbit carotid arteries with and without topically applied low-dose beta-radiation.nnnMETHODSnThe beta-emitting isotope strontium-90 (Sr-90) was conjugated onto the matrix of polypropylene (PLYP) mesh. Rabbit carotid arteries were balloon-injured with a #2 embolectomy catheter. Six carotid arteries were wrapped with nonradioactive PLYP mesh (controls) and Sr-90 ( approximately 90 microCi) PLYP mesh in order to deliver low-dose radiation to the vessel wall from the external (adventitial) surface. Tissue was harvested at 6 weeks and processed for histologic examination.nnnRESULTSnThere was consistent blockade of fibrocellular neointima formation with virtually no neointima present in all treated segments, compared to moderate neointima formation in controls. Medial thinning and smooth muscle cell (SMC) necrosis were also associated with topical brachytherapy.nnnCONCLUSIONnbeta-Radiation applied by an externally wrapped PLYP mesh labeled with Sr-90 markedly suppressed neointima formation in an animal vascular surgical injury model. Further studies, however, are necessary to determine a suitable isotope and dosage for clinical application.

Evaluation of the redesigned conformable GORE TAG thoracic endoprosthesis for traumatic aortic transection

OBJECTIVEnTo evaluate the safety and effectiveness of the conformable GORE TAG thoracic endoprosthesis (CTAG) device (W. L. Gore and Associates, Flagstaff, Ariz) for the endovascular repair of traumatic aortic transections.nnnMETHODSnA prospective, nonrandomized, multicenter trial was conducted at 21 sites. Primary safety end points included 30-day all-cause mortality. The effectiveness end point was freedom from a major device event requiring reintervention through 1-month follow-up.nnnRESULTSnFifty-one subjects were enrolled between December 2009 and January 2011 with polytraumatic injuries and a mean Injury Severity Score of 32 ± 14. The proximal mean intimal aortic diameter measured 24 mm, while the mean distal intimal diameter was 22 mm. A total of 57 CTAG devices were implanted (mean, 1.1/subject; range, 1-2) with a mean patient age of 44 years (range, 21-87) and a male-to-female ratio of 2:1. Technical success was 100% with an operative mortality of 0%. Femoral access was utilized in 96% of patients. The mean procedure time and blood loss was 105 minutes and 148 mL, respectively. All subjects required admission to an intensive care unit with a mean hospital stay of 14.6 days. Adjuvant techniques (ie, lumbar drains and induced hypertension) to prevent paraplegia were used in only 7.8% of patients. No patient developed paraplegia despite 63% having complete or partial left subclavian artery coverage and only 9% of those receiving left subclavian artery revascularization. In addition, there were no device compressions or major device events reported. Overall mortality at 30 days was 7.8%, and all were adjudicated by the clinical events committee as not being device or procedure related. Serious adverse events occurred in 39.2% of patients through 30 days. To date, there have been no conversions to open repair. Two site-reported endoleaks were detected during the mean follow-up of 4.2 months, which did not require reintervention.nnnCONCLUSIONSnThe CTAG device was demonstrated to be a safe and effective treatment for traumatic aortic transection based on 30-day outcomes. There were no device-related serious adverse events.

Role of MT1-MMP in Estrogen-Mediated Cellular Processes of Intimal Hyperplasia

BACKGROUNDnHormone replacement therapy increases intimal hyperplasia (IH) following vascular intervention. Matrix metalloproteinases (MMPs) play a role in IH development. We have shown estrogen up-regulates MT1-MMP expression, a transmembrane protein that activates MMP-2, and increases vascular smooth muscle cell (VSMC) collagen invasion via increased MMP-2 activity. Here we hypothesize inhibition of MT1-MMP will prevent hormonally-stimulated increased MMP-2 activation and the downstream cellular processes of IH pathogenesis.nnnMETHODSnVSMCs from a postmenopausal donor were transfected with MT1-MMP or negative control siRNAs, treated with estrogen (Est), analyzed by q-PCR, Western blot, zymography, migration, invasion, and proliferation assays.nnnRESULTSnEst treatment of MT1-MMP silenced cells still resulted in increased MT1-MMP expression (C = 41% ± 4%; Est = 52% ± 2%; P < 0.05). Silencing of MT1-MMP decreased basal MMP-2 activity (nonsilenced = 100%; MT1-silenced = 87% ± 3%; P < 0.05) but had no effect on basal invasion or proliferation. Est treatment of MT1-MMP silenced cells still resulted in increased MMP-2 activity (C = 87% ± 3%; Est = 101% ± 4%; P < 0.05) and invasion (C = 89% ± 6%; Est = 109% ± 3%; P < 0.05) compared with MT1-MMP silenced control cells. However, silencing of MT1-MMP did inhibit Est- and serum-stimulated proliferation (C = 106% ± 18%; Est = 104% ± 16%; FBS = 121% ± 24%; P = NS).nnnCONCLUSIONnSilencing of MT1-MMP in aged VSMCs results in impaired but not complete inhibition of basal and Est-stimulated increases in MMP-2 activity. Other mechanisms appear to be playing a role in hormonally-regulated cellular processes of IH pathogenesis. Future studies will target other signaling cascades, with the goal of identifying mechanisms responsible for hormonally-modulated unbalanced MMPs. In vivo manipulation of the expression patterns of MT1-MMP will be examined for the prevention of IH in animal models of vascular disease.

Serum Levels of Matrix Metalloproteinase-2 as a Marker of Intimal Hyperplasia

BACKGROUNDnA primary component in the development of intimal hyperplasia (IH) in response to vascular injury is basement membrane remodeling. Matrix metalloproteinases (MMPs) play a major role in this process by degradation of basement membrane proteins, mainly collagen type IV. Vascular injury initiates an inflammatory cascade with the release of tumor necrosis factor-alpha (TNFalpha), interleukin-1beta (IL-1beta), and C-reactive protein (CRP). We hypothesize serum levels of these elements may serve as biomarkers of the development of IH.nnnMETHODS AND RESULTSnAt baseline, 2, 7, 10, and 14 days post-balloon angioplasty of the carotid artery, rat tissue samples were stained with Masson trichrome elastin to examine IH. Intima:media ratios (I:M) increased significantly over time postinjury. Serum samples were collected at the time of tissue sampling, and levels of MMP-2, MMP-9, collagen type IV, TNFalpha, IL-1beta, and CRP were assayed using sandwich enzyme-linked immunosorbent assay (ELISA). MMP-2 serum levels at 7, 10, and 14 days postinjury were significantly elevated compared with baseline. Other elements were not significantly elevated.nnnCONCLUSIONnEarly and persistent elevation in the serum levels of MMP-2 may be a useful biomarker of basement membrane remodeling and the presence of IH.

Contemporary outcomes of vertebral artery injury

OBJECTIVEnVertebral artery injury (VAI) associated with cervical trauma is being increasingly recognized with more aggressive screening. Disparate results from previous literature have led to uncertainty of the significance, natural history, and optimal therapy for VAI.nnnMETHODSnTo understand the natural history and treatment outcomes from our experience, we performed a retrospective, single-center review from a level I trauma center for the previous 10 years of all VAI. Injuries were identified from search of an administrative trauma database, a resident-run working database, and all radiology dictations for the same period. All VAI were classified according to segmental involvement, Denver grading scale, and laterality. Analysis of associated injuries, demographics, neurologic outcome, mortality, length of stay, treatment plan, and follow-up imaging was also performed.nnnRESULTSnFifty-one patients with VAI were identified from 2001 to 2011 from a total of 36,942 trauma admissions (0.13% incidence). Associated injuries were significant with an average New Injury Severity Score of 29.6. Penetrating trauma occurred in 14%. Cervical spine fracture was present in 88% with VAI. Diagnosis was obtained with computed tomographic angiography (CTA) in 95%. Screening was prompted by injury pattern or high-risk mechanism in all cases. Injuries classified according to the Denver grading scale were grade I = 24%, grade II = 35%, grade III = 4%, grade IV = 35%, and grade V = 2%. Distribution across segments included V1 = 18%, V2 = 67%, V3 = 31%, and V4 = 6%. Only one posterior circulation stroke was attributable to VAI. Overall mortality was 8%, with each mortality being associated with significant other organ injuries. Treatment rendered for VAI was antiplatelet therapy (50%), observation (31%), warfarin (17%), and stent (2%). There were no significant differences between treatment groups on any variable with the exception of body mass index (P = .047). Follow-up was obtained for 13% (n = 6) of survivors. The CTA demonstrated injury stability in four patients and resolution in two patients. Accuracy of the administrative trauma database was 53% compared with 96% for the resident-run working database.nnnCONCLUSIONSnNeurologic sequelae attributable to VAI were rare. Grade of VAI or vertebral artery segment did not correlate with morbidity. We did not observe any differences in short-term outcomes between systemic anticoagulation and antiplatelet therapy. Of those patients seen at follow-up, injury resolution or stability was documented by CTA. A conservative approach with either observation or antithrombotic therapy is suggested. If the natural history of VAI includes a very low stroke rate, then therapies with a lower therapeutic index, such as systemic anticoagulation, in the severely injured trauma patient are not supported. Our search strategy urges awareness of the limitations of administrative databases for retrospective vascular study.

The excluder aortic endograft.

Since its introduction, more than 59000 patients have been treated with Gore Excluder endoprosthesis (GORE) for abdominal aortic aneurysm (AAA) in the past 11 years. It has become clearer that differences in device delivery and design provide certain advantages that may favor one anatomical milieu over another. Behavior of the aneurysm sac also seems to be graft dependent as more long-term data become available. The currently available low-permeability GORE seems to have addressed the problem of endotension noted with previous designs. Cumulative data are reviewed, and the data demonstrate very low perioperative morbidity and mortality and excellent protection from aneurysm-related complications with the GORE device. Superior ease of use, excellent trackability, and rare failures requiring acute open conversion characterize the GORE device. By addressing clinical demands of aortic endografting, Gore has eclipsed other endografts in the industry to now dominate the US market. The aim of this review is to describe the history, experience, advantages, and future goals with the GORE for the treatment of AAA.