W. Brent Keeling

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.

Long-term survival for patients with preoperative renal failure undergoing bioprosthetic or mechanical valve replacement.

BACKGROUND The objective of this study was to assess short-term and long-term outcomes after valve replacement with biologic or mechanical prostheses in patients with preoperative end-stage renal disease on chronic dialysis. METHODS A retrospective review of patients with end-stage renal disease undergoing valve replacement from January 1996 through March 2008 at Emory Healthcare Hospitals was performed. Outcomes were compared using χ(2) tests and 2-sample t tests. Adjusted long-term survival up to 10 years was assessed with Kaplan-Meier plots and compared between biologic and mechanical replacements using the Cox proportional hazards model. RESULTS A total of 202 patients underwent 211 valve replacement operations. Patient age was 20 to 83 years (mean age, 54.8 ± 14.0); 115 of 211 (54.5%) were male. Operations included the following: 100 of 211 (47.4%) isolated aortic; 49 of 211 (23.2%) isolated mitral; 4 of 211 (1.9%) isolated tricuspid; and 58 of 211 (27.5%) combined replacements. Thirteen (6.2%) patients underwent reoperative valve replacements. Most patients received bioprosthetic valves (143 of 211, 67.8%), while 68 of 211 (32.2%) received mechanical valves. Concomitant coronary artery bypass was performed in 53 of 211 (25.1%) patients. Thirty-day mortality was in 42 of 211 patients (19.9%) and was not different between bioprosthetic and mechanical replacements. Overall 10-year survival was 18.1% for all patients and was not influenced by valve type implanted. CONCLUSIONS For patients with end-stage renal disease treated with dialysis, valve replacement carries acceptable operative mortality. Long-term survival is similar among patients receiving bioprosthetic versus mechanical valve replacement. Careful risk assessment and choice of valve prosthesis should be performed prior to surgical intervention in this high-risk patient population.

Regional antibiotic delivery for the treatment of experimental prosthetic graft infections.

OBJECTIVES To evaluate the efficacy of antibiotic-impregnated polymethylmethacrylate (PMMA) beads in eradication of an arterial prosthetic graft methicillin-resistant Staphylococcus aureus (MRSA) biofilm in an experimental animal model. METHODS Forty rats underwent subcutaneous implantation of a MRSA-colonized arterial polytetrafluoroethylene (PTFE) 1 x 1 cm wafer on the back. The effect of regional antibiosis produced by antibiotic PMMA bead placement adjacent to the infected PTFE wafer was determined using four 10-animal study groups: control (no antibiotic), PMMA bead with no antibiotic, PMMA bead with 10% vancomycin, and PMMA bead with 10% daptomycin. After 3 d, the PTFE wafers were explanted and quantitative biofilm cultures, expressed as colony-forming units (CFU) per graft wafer, performed using real-time polymerase chain reaction to assess MRSA eradication. No systemic antibiotic was administered. Bioassays of antibiotic bead bacteriocidal were performed by measuring zone of inhibition diameters on MRSA colonized agar culture plates prior to and following graft explantation. RESULTS All animal tolerated implantation of the MRSA-infected PTFE wafer and survived the 3 d until graft explantation. Quantitative biofilm cultures demonstrated a significant decrease (P < 0.01) in MRSA CFUs present on the PTFE wafer surfaces in the presence of both the vancomycin- and daptomycin-impregnated beads compared to controls and plain PMMA beads. Both vancomycin and daptomycin PMMA beads retained antibacterial activity after 3 d of implantation with decrease in zones of inhibition of 15% and 45%, respectively. CONCLUSIONS Regional antibiotic delivery using an antibiotic-impregnated PMMA bead reduced the bacterial biofilm concentration in experimental subcutaneous pocket model of vascular surgical site infection. The delivery of antibiotics via a PMMA bead may be a useful adjunct in the treatment of vascular surgical site infection.

Superior Mesenteric Artery Stent Fracture Producing Stenosis and Recurrent Chronic Mesenteric Ischemia: Case Report

Endovascular modalities are being increasingly employed in the treatment of a variety of vascular diseases. With new technologies come novel complications, and one such complication unique to endovascular surgery is stent fracture. We present two cases of stent fracture following stenting of the superior mesenteric artery and discuss possible causes and treatments.

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.

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.

A Novel Stentless Mitral Valve

Stentless mitral valves have found little clinical utility to date due to difficulty in insertion. A new design for a stentless mitral valve, a modification of an existing aortic stentless prosthesis, is described. The new design mimics the native mitral physiology, and its insertion is easier than with existing stentless mitral valves. Commercially available stentless aortic valves were inserted into 2 pigs. The valves were modified so that the commissural posts were restrained. The valves were partially recessed into the left ventricular cavity, secured to the annulus, and anchored to the native papillary muscles. Both pigs were weaned from bypass successfully, and both valves functioned normally with trace regurgitation noted on echocardiography. This design affords the benefit of the reapproximation of native physiology. Preservation of papillary-annular continuity should allow maximal left ventricular function. Lack of a stent should allow avoidance of long-term anticoagulation.