Paul A. Armstrong

An Overview of Matrix Metalloproteinases in the Pathogenesis and Treatment of Abdominal Aortic Aneurysms

Recent basic and clinical research has established a link between the pathogenesis of abdominal aortic aneurysms (AAA) and matrix metalloproteinases (MMP). The discovery of the influence of MMPs on in vitro and in vivo aneurysm development has yielded promising information that may eventually decode the pathogenetic factors affecting the initiation and growth rate of AAAs. In this review, an analysis of MMPs involved in AAA disease is presented, including the data from recent research studies and planned clinical drug trails designed to retard the AAA growth by inhibiting MMP activity.

Current Indications for Preoperative Inferior Vena Cava Filter Insertion in Patients Undergoing Surgery for Morbid Obesity

Background: Pulmonary embolus is a potentially lethal complication in patients undergoing surgery for morbid obesity. In a select group of patients at high risk for venous thromboembolic events (VTE), we have chosen to prophylactically insert inferior vena cava filters via a jugular percutaneous approach. We propose guidelines for preoperative insertion of inferior vena cava filters in patients with clinically significant obesity. Methods: All patients who underwent preoperative insertion of inferior vena cava (IVC) filters as prophylaxis for pulmonary emboli were reviewed. Data regarding body mass index (BMI), prior history of venous thromboembolism, current anticoagulant usage, as well as other patient data were compiled and analyzed. Additionally, all operative notes were reviewed, and operative data were analyzed and compared. Results: 14 patients underwent preoperative IVC filter placement before gastric bypass. Mean patient age was 49.1 ± 1.52 years and mean BMI was 56.5 ± 4.45 kg/m2. No complications occurred due to preoperative filter placement, and no pulmonary emboli occurred in this group. Indications for preoperative IVC filter insertion included prior pulmonary embolus (6), prior deep venous thrombosis (7), and lower extremity venous stasis (1). Conclusions: Vena caval filter placement in the preoperative period can be undertaken safely in bariatric patients. We recommend that routine preoperative vena caval filter placement should be undertaken in all bariatric patients with prior pulmonary embolus, prior deep venous thrombosis, evidence of venous stasis, or known hypercoagulable state. Possible roles for IVC filter placement in this patient population are expanding as more data is acquired.

Important surgical considerations in the management of renal cell carcinoma (RCC) with inferior vena cava (IVC) tumour thrombus.

Whats known on the subject? and What does the study add?

Visceral Duplex Scanning: Evaluation Before and After Artery Intervention for Chronic Mesenteric Ischemia

Color duplex ultrasound testing has evolved to be a clinically useful modality to diagnose chronic mesenteric ischemia caused by visceral artery origin atherosclerosis. Testing requires expertise in ultrasound imaging, visceral artery hemodynamics, and duplex scan interpretation. Patient can be accurately screened for severe stenosis or occlusion involving celiac, superior mesenteric, or inferior mesenteric arteries. Duplex testing can also evaluate functional patency following visceral bypass grafting procedures or endovascular stent-angioplasty. The focus of duplex surveillance after visceral artery intervention is to identify severe repair site stenosis, which can develop with symptoms of gut ischemia. Visceral duplex testing of a bypass graft or stent-angioplasty site that shows peak systolic velocities >300 cm/s with end-diastolic velocities >50 to 70 cm/s, or a decreased graft velocity peak systolic velocity <40 cm/s should be considered for interrogation using angiography to confirm or exclude severe (>70%) stenosis. Duplex testing after surgical or endovascular visceral interventions is a screening study, which compliments clinical follow-up by aiding the vascular surgeon in timely identification of visceral repairs that have developed a progressive, high-grade stenosis.

Graft Infectivity of Rifampin and Silver-Bonded Polyester Grafts to MRSA Contamination

The purpose of this study was to evaluate the ability of vascular polyester grafts with antibacterial properties to resist colonization following surface contamination by methicillin-resistant Staphylococcus aureus(MRSA) in an experimental canine model or aortic graft infection. Twenty-four pathogen-free dogs underwent replacement of the infrarenal aorta with either a rifampin-soaked (30 mg/mL) or silver-impregnated (Ag-acetate) woven polyester graft. Following implantation, the external graft surface was inoculated with 2 mL of 107 colonyforming units/mL (CFU) of MRSA. Preoperative antibiotic prophylaxis consisted of a single intravenous dose of 500 mg of sodium cefazolin. Four grafts of each type were explanted at 3, 7, and 14 days after implantation. Quantitative cultures (CFU/specimen) of perigraft fluid (1 mL), graft material (1 cm segment), and adjacent aorta (1 cm segment) were performed. Differences between grafts are expressed as% mean log reduction in recoverable CFU compared to the inoculation solution concentration of 107 CFUs. At 3 days, explanted rifampinsoaked grafts exhibited no MRSA growth (4 of 4 grafts) and a =97% mean log reduction of MRSA CFUs from the adjacent aorta and perigraft fluid (PGF). At 3 days, all silver-bonded grafts exhibited signs of infection and a mean log CFU reduction of MRSA ranging from 68% (absolute range 101–103 recoverable CFU) for the graft, 79% (absolute range 101–103 recoverable CFU) for the aorta, and 86% (absolute range 101–104 recoverable CFU) for PGF. The 7-day rifampin group had an average log reduction in MRSA CFU of 72% (graft), 58% (PGF), 75% (aorta). Quantitative cultures of 14-day rifampin grafted demonstrated continued bacterial growth suppression with mean MRSA CFU log reductions of 82%, graft; 72%, PGF; 89%, aorta. Silver-bonded grafts demonstrated <50% mean CFU reduction in MRSA growth at 7 days (absolute range 105–107 recoverable CFU) and 14 days (absolute range 103–107 recoverable CFU). No animal died from sepsis or anastomotic hemorrhage. Neither rifampin nor silverbonded grafts demonstrated prolonged resistance to surface MRSA contamination. Rifampinsoaked polyester grafts exhibited a marked but transient resistance MRSA colonization likely the result of high antibiotic concentration in the perigraft tissue. While both types of grafts failed to eradicate the MRSA infection future research with silver-bonded grafts that have an additional antibiotic attached may have a place in the treatment of MRSA infection.

Increasing Endovascular Intervention for Claudication: Impact on Vascular Surgery Resident Training

Purpose: To audit the caseloads of vascular surgery residents in the management of disabling claudication and assess the influence of endovascular procedures on overall operative experience. Methods: A retrospective review was conducted of vascular surgery resident experience in the open and endovascular management of lower limb claudication during two 3-year periods (January 2000 to December 2002 and January 2003 to December 2005). The time periods differed with regard to number of surgical faculty with advanced endovascular skills (3 in the first period and 4 in the second) and the availability of portable operating room angiography equipment. Results: During the 6-year period, the operative logs of vascular surgery residents indicated participation in 283 procedures [170 (60%) open surgical interventions, including 146 suprainguinal procedures] performed for claudication. The number of procedures increased by 62% (p<0.05) from the first period (n=108) to the second (n=175). Endovascular intervention to treat aortoiliac occlusive disease increased 4-fold (14 versus 56 interventions, p=0.01) compared to a decrease in open (bypass grafting, endarterectomy) surgical repair (45 to 31 procedures, p=0.22). The greatest change in resident experience was in endovascular intervention of infrainguinal occlusive disease: the case volume increased from 4 to 39 procedures (p=0.07) during the 2 time intervals. By contrast, the number of open surgical bypass procedures was similar (45 versus 49) in each 3-year period. Conclusion: An audit of resident experience demonstrated intervention for claudication has increased during the past 6 years. The increased operative experience reflects more endovascular treatment (atherectomy, angioplasty, stent-graft placement) of femoropopliteal and aortoiliac occlusive disease, but no decrease in open surgical operative experience for claudication. This increase in endovascular intervention may be related to a decrease in the threshold for intervention.

Evolving Microbiology and Treatment of Extracavitary Prosthetic Graft Infections

The authors report the microbiology and outcomes following an individualized treatment algorithm for extracavitary (EC) prosthetic graft infection, including the use of graft preservation and in situ graft replacement techniques. A retrospective 8-year review of 87 patients treated for EC prosthetic graft infections was carried out. The treatment algorithm included culture-specific antibiotic therapy, surgical site debridement with antibiotic bead placement, selected graft preservation with muscle flap coverage, or graft excision with in situ conduit replacement. Outcomes measured included death, limb loss, and recurrent infection. It was found that present-day management of EC prosthetic graft infections is associated with lower mortality and morbidity despite changes in microbiology and the increased application of graft preservation and in situ grafting treatments.

Randomized controlled trial comparing the safety and efficacy between the FUSION BIOLINE heparin-coated vascular graft and the standard expanded polytetrafluoroethylene graft for femoropopliteal bypass

OBJECTIVE Despite improvements in endovascular therapy for lower extremity arterial disease, open surgical revascularization is still required when the disease is extensive. Although autogenous vein is the conduit of choice for open femoropopliteal bypass, prosthetic grafts can be an acceptable alternative when adequate vein is not available. The FUSION BIOLINE heparin-coated vascular graft (Maquet Endovascular, Wayne, NJ) was developed to improve the patency rate associated with standard prosthetic grafts. The current study, the FINEST Trial (Comparison of Safety and Primary Patency Between the FUSION BIOLINE Heparin-Coated Vascular Graft and EXXCEL Soft ePTFE), was designed to assess the clinical outcome of heparin-coated and standard vascular grafts in a prospective, randomized, controlled, multicenter trial. METHODS During a 25-month period ending in June 2012, 209 eligible patients scheduled to undergo elective prosthetic femoral to above-knee or below-knee popliteal bypass were randomized to receive a standard expanded polytetrafluoroethylene (ePTFE) graft or the heparin-coated FUSION BIOLINE vascular graft. Among 203 patients in the efficacy analysis, claudication was the presenting symptom in 147 (72.4%), and the site of the distal anastomosis was at the above-knee level in 174 (85.7%). Grafts were assessed by duplex ultrasound imaging and ankle-brachial indices performed postoperatively at discharge and at 30 days, 6 months, and 12 months. The primary efficacy end point was primary patency of the study graft. The primary safety end point was the composite of major adverse events and periprocedural death. Secondary end points included the time to hemostasis of bleeding at the anastomotic suture hole and primary assisted and secondary patency. RESULTS The primary patency rates at 6 months were 86.4% for the FUSION BIOLINE heparin-coated vascular graft group compared with 70.0% for the standard ePTFE group, a difference of 16.4% (95% confidence interval, 2.7%-29.9%; P = .006), and the respective rates at 12 months were 76.5% and 67.0% (95% confidence interval, -4.8% to 23.0%; P = .05). The mean time to hemostasis of bleeding at the suture hole was 3.5 minutes in the FUSION BIOLINE group and 11.0 minutes in the standard ePTFE group (P < .0001). Major adverse events were significantly lower in the FUSION BIOLINE group, occurring in 17.1%, compared with 30.7% in the standard ePTFE group (P = .033), principally a result of a lower rate of major graft reinterventions through 12 months in the FUSION BIOLINE group (16.2% vs 30.7%). CONCLUSIONS Data from this randomized multicenter study demonstrated improved midterm patency, less bleeding at the suture hole, and lower major adverse events with the FUSION BIOLINE heparin-coated vascular graft compared with standard ePTFE grafts. Although the ultimate long-term benefit of the graft cannot be ascertained with the data currently available, the utility of the FUSION BIOLINE vascular graft appears promising.

Pseudoaneurysm of the Superficial Femoral Artery Associated with Osteochondroma A Case Report

Osteochondromas, the most common benign bone tumor, often go undetected and seldom cause significant clinical sequelae. Rarely they present as an arterial pseudoaneurysm, usually of the popliteal or superficial femoral artery. The authors present the case of a 14-year-old male with a distal superficial femoral artery pseudoaneurysm accompanied by distal embolization from a femoral exostosis.

Renal cell carcinoma accompanied by venous invasion and inferior vena cava thrombus: classification and operative strategies for the vascular surgeon

Venous invasion is a common characteristic of renal cell carcinoma, manifesting as tumor thrombus with possible extension into the renal vein and, in extensive cases, the thrombus can reach from the renal vein to the right atrium. Currently, cytoreductive nephrectomy and tumor thrombectomy are the foundations for improving quality of life and survival in the treatment of renal cell carcinoma, and a role has emerged for a vascular specialist to become an integral part of operative planning and therapy.