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Biomedical subjects

Alan B Lumsden

Publications and source records attributed to Alan B Lumsden.

At least 73 records · Page 4Linked to original sources
PubMed2004

Abdominal aortic surgery in patients with human immunodeficiency virus infection.

PURPOSE: Human immunodeficiency virus (HIV) infection is known to cause acquired immune deficiency syndrome, which has been associated with a wide array of cardiovascular pathologies. This report examined the clinical outcome of patients infected with HIV who underwent abdominal aortic reconstruction for aneurysm or occlusive disease. METHODS: Hospital and clinic records of all patients with HIV infection who underwent an abdominal aortic operation were reviewed during an 11-year period. Relevant risk factors and clinical variables were assessed for surgical outcome. RESULTS: Forty-eight HIV patients (mean age 54 +/- 13 years) were identified who underwent abdominal aortic bypass grafting during the study period. Indications for aortic operation included aneurysm (n = 20) and aortoiliac occlusive disease (n = 28). All patients underwent successful aortic reconstructions without intraoperative mortality. Postoperative complications and in-hospital mortality occurred in 16 patients (33%) and 7 patients (15%), respectively. The mean follow-up period was 41 months. Life-table survival rates in aneurysm and occlusive patients at 60 months were 43.2% +/- 5.3% and 46.3% +/- 7.4% (not significant), respectively. Multivariate analysis showed that low CD4 lymphocyte counts (< 200/microL, P <0.05) and hypoalbuminemia (<3.5 g/dL, P <0.05) were risk factors for postoperative complications. CONCLUSION: Perioperative morbidity and mortality rates are high in HIV patients undergoing an abdominal aortic operation. Low CD4 lymphocyte counts and hypoalbuminemia are associated with poor clinical outcomes in HIV patients undergoing abdominal aortic reconstruction.

Adult↗
PubMed2004

Aortic endograft thrombosis after colorectal surgery in lithotomy position.

Aortic endograft limb occlusion is a serious complication after endovascular abdominal aortic aneurysm repair. We describe a yet unreported cause of endograft limb occlusion, the lithotomy position. Two patients with abdominal aortic aneurysm and colorectal cancer underwent an initial endovascular repair followed by cancer resection in the lithotomy position. Aortic endograft limb occlusion occurred in both patients immediately after the cancer operation. Percutaneous rheolytic thrombectomy was performed successfully in both patients. Pelvic surgery requiring the lithotomy position should be performed with caution in patients with aortic endografts, because it can result in endograft occlusion.

Aged↗
PubMed2004

Small-caliber heparin-coated ePTFE grafts reduce platelet deposition and neointimal hyperplasia in a baboon model.

PURPOSE: Intimal hyperplasia and graft thrombosis are major causes of graft failure. Heparin prolongs graft patency and inhibits neointimal hyperplasia in animal models. The purpose of this study was to evaluate the effect of a heparin-coated expanded polytetrafluoroethylene (ePTFE) graft on platelet deposition and anastomotic neointimal hyperplasia after aortoiliac bypass grafting in a baboon model. METHODS: Heparin-coated ePTFE grafts (4-mm diameter) were incorporated into exteriorized femoral arteriovenous shunts placed in five baboons. Platelet deposition was analyzed by measuring the accumulation of indium 111-labeled platelets on the grafts, with dynamic scintillation camera imaging. Eight adult male baboons (mean weight, 9.3 kg) underwent bilateral aortoiliac bypass grafting with ePTFE grafts (4-mm internal diameter). In each animal a heparin-coated ePTFE graft was placed in one aortoiliac artery, and an uncoated graft, which served as the control, was placed in the contralateral aortoiliac artery. All grafts were harvested at 4 weeks, and were analyzed quantitatively for neointimal hyperplasia at graft-vessel anastomoses. RESULTS: Early platelet deposition on heparin-coated grafts after 1 to 4 hours of ex vivo circuitry was significantly reduced. All the harvested aortoiliac grafts were patent at 4 weeks. There was a significant reduction in neointimal area at both proximal (0.26 +/- 0.11 mm(2)) and distal (0.29 +/- 0.14 mm(2)) anastomoses in the heparin-coated grafts, compared with proximal (0.56 +/- 0.18 mm(2)) and distal (0.63 +/- 0.21 mm(2)) anastomoses in the untreated control grafts (P <.05). In addition, neointimal cell proliferation assayed with bromodeoxyuridine (BrdU) incorporation was reduced in the graft neointima (3.47% +/- 0.43%) in heparin-coated grafts compared with the graft neointima (6.21% +/- 0.59%) in untreated control grafts (P <.05). CONCLUSIONS: Small-caliber heparin-coated ePTFE grafts significantly reduce platelet deposition and anastomotic neointimal hyperplasia and cell proliferation, without measurable side effects, in baboons. Surface coating with heparin in small-caliber ePTFE grafts is useful for improving prosthetic bypass graft patency. CLINICAL RELEVANCE: An autologous vein graft is the ideal bypass conduit in peripheral arterial reconstruction; however, many patients who undergo bypass grafting do not have adequate or available autologous vein graft. As a result surgeons often must rely on prosthetic grafts as an alternative conduit in arterial bypass procedures. Clinical outcomes with prosthetic grafts in peripheral arterial reconstruction are generally inferior to those with autologous vein bypass grafts, in part because of anastomotic neointimal hyperplasia. This study evaluated the effect of small-caliber heparin-coated expandable polytetrafluoroethylene (ePTFE) grafts in aortoiliac reconstruction in a baboon model. The study found that heparin-coated ePTFE grafts resulted in less intimal hyperplasia and less platelet deposition after implantation, compared with noncoated control ePTFE grafts.

Anastomosis, Surgical↗
PubMed2004

Radiation-associated venous stenosis: endovascular treatment options.

We report a case of radiation-induced venous stenosis after pelvic irradiation to treat Paget's disease of the scrotum. During therapeutic anticoagulation, significant left lower extremity swelling developed due to an iliofemoral deep venous thrombosis (DVT). After percutaneous thrombectomy and thrombolysis, a high-grade stenosis was uncovered in the left external iliac vein, which was treated with an endoluminal stent. However, ipsilateral DVT recurred 2 months later despite continued anticoagulation therapy. Repeat treatment was successful. Pelvic radiation is a potential cause of iliac vein stenosis. Pharmacomechanical thrombectomy may have a useful role in management of complex iliofemoral DVT.

Aged↗
PubMed2004

Acute arterial thrombosis associated with cocaine abuse.

PURPOSE: Cocaine-induced arterial thrombosis is uncommon, and most reported cases involved small-diameter vessels such as the cerebral and coronary arteries. This study was undertaken to review our experience with peripheral arterial thrombosis presumed caused by cocaine abuse. METHODS: Hospital records were reviewed for all patients admitted over 10 years with acute arterial occlusion involving the peripheral arterial system. Patients with confirmation of cocaine use or of its derivative, crack cocaine, within 24 hours of hospital admission formed the basis of this study. Symptoms at presentation, management, and outcome in these patients were reviewed. RESULTS: Three hundred eighty-two patients with acute peripheral arterial occlusion were identified during the study period. The presumptive diagnosis of cocaine-induced arterial occlusion was made in 5 patients (4 men, mean age 38 years). Cocaine use was achieved via intranasal inhalation in 2 patients (40%), whereas the 3 remaining patients smoked crack cocaine (60%). The mean time between cocaine use and onset of arterial thrombosis was 9.2 hours (range, 2-20 hours). Symptoms at presentation included acute limb ischemia without pedal Doppler signals (3 patients, 60%) and abdominal pain without femoral pulses (2 patients, 40%). Arterial occlusion was confirmed on angiograms in all patients, which revealed aortic thrombosis in 1 patient (20%), iliac thrombosis in 2 patients (40%), superficial femoral artery thrombosis in 1 patient (20%), and popliteal artery occlusion in 1 patient (20%). Surgical thrombectomy was successfully performed in 4 patients (80%), and 1 patient (20%) underwent successful thrombolytic therapy for femoropopliteal artery occlusion. There was no perioperative mortality. All 5 patients who were discharged were available for follow-up (mean, 36 months; range, 6-75 months). There was 1 late death from myocardial infarction. In 1 patient recurrent lower extremity arterial thrombosis developed after 28 months, which was successfully treated with thrombolytic therapy. CONCLUSIONS: Our study underscores cocaine abuse as a potential cause of acute arterial thrombosis. Cocaine-induced arterial thrombosis should be suspected in patients with recent history of cocaine abuse with acute limb ischemia without an identifiable source or overt cardiovascular risk factors. Prompt angiography with operative or endovascular intervention should be performed to avert arterial ischemic sequelae.

Adult↗
PubMed2004

Pharmacomechanical thrombectomy for treatment of symptomatic lower extremity deep venous thrombosis: safety and feasibility study.

PURPOSE: The current standard of care for deep venous thromboembolism (DVT) is anticoagulation; however, this treatment method does not rapidly relieve clot burden or clinical symptoms. We describe a rapid and effective method of thrombus removal, with simultaneous percutaneous mechanical thrombectomy (PMT) and thrombolysis. METHODS: Over 26 months 20 patients (22 men, 2 women; mean age, 52 +/- 6 years [range, 38-79 years]) with extensive lower extremity DVT were treated with PMT with the AngioJet thrombectomy device in combination with lytic agent (urokinase, tissue plasminogen activator, or reteplase) added to the infusion. Three patients underwent treatment twice, because of recurrent DVT. The primary end point was angiographic evidence of restoration of venous patency at completion of the procedure. Complications, recurrent ipsilateral DVT, and improvement in clinical symptoms were evaluated. RESULTS: Complete thrombus removal was obtained in 15 procedures (65%), and partial resolution in the remaining 8 procedures (35%). Inciting occlusive lesions responsible for acute DVT were revealed in 14 patients (61%), and angioplasty with or without stenting was performed when necessary. In the 8 procedures with partial resolution additional catheter-directed thrombolysis was carried out on average for 5.7 hours, with further thrombus reduction. Overall, immediate (<24 hours) improvement in clinical symptoms was noted in 17 patients (74%). There were no complications related to either PMT or the short duration of lytic agent infusion. At average follow-up of 10.2 +/- 0.3 months (range, 3-26 months), 3 patients had recurrent ipsilateral DVT, and underwent repeat treatment. CONCLUSIONS: Addition of lytic agent to PMT facilitates thrombus extraction, decreases overall interventional treatment time, and improves patient outcomes. In addition, definitive management of underlying anatomic lesions can be performed in the same setting. Further outcome measures are necessary to study the long-term efficacy of this treatment method on preservation of valve function, reduction of chronic venous insufficiency, and improved quality of life.

Adult↗
PubMed2004

Curcumin blocks homocysteine-induced endothelial dysfunction in porcine coronary arteries.

PURPOSE: Curcumin, a yellow polyphenolic compound from the plant Curcuma ionga , is a commonly used spice and coloring agent with beneficial effects of anti-tumor, anti-inflammatory, and antioxidant activities. The objective of this study was to determine the effect of curcumin on homocysteine-induced endothelial dysfunction in a porcine coronary artery model. METHODS: Porcine coronary arteries were cut into 5-mm rings, which were incubated for 24 hours either as control rings, with homocysteine (50 micromol/L), curcumin (5 micromol/L), or a combination of curcumin (5 micromol/L) and homocysteine (50 micromol/L). Myograph tension analysis was performed in response to vessel active drugs including thromboxane A2 analog U466419 (contraction), endothelium-dependent vasorelaxation (bradykinin), and endothelium-independent vasorelaxation (sodium nitroprusside). Immunohistochemical staining was performed for endothelial nitric oxide synthase (eNOS). In addition, superoxide anion production was determined by lucigenin-enhanced chemiluminescence. RESULTS: All groups of porcine coronary artery rings showed no difference in maximal contraction after U46619 challenge. However, endothelium-dependent vasorelaxation in response to 10(-5) mol/L bradykinin was 40% in the homocysteine-treated group, as compared to 73% in the control group (P = .03). Of importance, curcumin could effectively block homocysteine-induced impairment of endothelium-dependent vasorelaxation. All groups showed no difference in endothelium-independent vasorelaxation. In addition, eNOS immunoreactivity was reduced in the homocysteine group, but the combined homocysteine and curcumin group showed eNOS levels comparable to those in the control group. Furthermore, superoxide anion levels of the endothelial layer were significantly increased by 2-fold in homocysteine-treated vessels as compared to control vessels (P = .02), whereas curcumin could block the effect of homocysteine on superoxide anion production. CONCLUSION: These data demonstrate that curcumin effectively reverses the endothelial dysfunction induced by homocysteine. In addition, curcumin significantly blocked homocysteine-induced superoxide anion production and eNOS down-regulation. This study suggests a therapeutic role for dietary curcumin in patients with homocysteinemia, thereby reducing cardiovascular morbidity and mortality. CLINICAL RELEVANCE: Hyperhomocysteinemia is a significant clinical problem. It is an independent risk factor for cardiovascular diseases. This study provides new information for better understanding the molecular mechanisms of homocysteine-induced vascular injury. More importantly, curcumin, a natural substance, can effectively block the detrimental effect of homocysteine on the vascular system. Thus curcumin could be used in patients with hyperhomocysteinemia, and to prevent cardiovascular diseases.

Animals↗
PubMed2004

What is new in the preoperative evaluation of arteriovenous access operation?

It is widely recognized that autogenous arteriovenous access is the preferred dialysis access of choice because of improved patency and low infection rate. It has been shown recently that preoperative ultrasound study to identify available venous conduits can increase the utilization of autogenous arteriovenous access. The article examines the clinical evidence to support this rationale and reviews the available portable ultrasound devices that enable surgeons to perform ultrasound examination in patients undergoing dialysis access operation.

Arteriovenous Shunt, Surgical↗
PubMed2004

Management of thrombosed dialysis access: thrombectomy versus thrombolysis.

More than 250,000 patients per year with end stage renal disease are maintained on long-term hemodialysis. Because of this large population, hemodialysis access procedures now account for a large percentage of operative interventions in the United States. Prosthetic arteriovenous access thrombosis is a frequent complication that occurs at a rate of 0.5 to 0.8 episodes per year and is a major source of hospital admissions, increasing hospital costs, patient morbidity, and physician frustration. Thrombosed grafts often require rescue procedures to extend the life of the graft and make the most use of the limited available access sites. Such salvage procedures of thrombosed prosthetic dialysis shunts may be performed with either conventional surgical or endovascular techniques. Many techniques for declotting have been used, including open surgical thrombectomy, percutaneous pharmacologic or mechanical thrombectomy, and pharmacomechanical techniques. Despite the various treatment options, no individual declotting modality has proven itself superior. Long-term patencies after a single revascularization procedure are meager, with a median of less than 90 days. This article will review prosthetic hemodialysis access graft declotting mechanisms and supporting literature.

Aortography↗
PubMed2004

Basic fibroblast growth factor coating and endothelial cell seeding of a decellularized heparin-coated vascular graft.

The objective of this study was to determine the effect of basic fibroblast growth factor (bFGF) coating on endothelial cell seeding and proliferation on a decellularized heparin coated vascular graft and to determine the retention of seeded cells on the graft under flow conditions. Disks of heparin coated decellularized grafts were incubated for 24 h as controls or with bFGF. Human microvascular endothelial cells (HMECs) or canine peripheral blood endothelial progenitor cells (CEPC) were seeded onto the disks and incubated for 96 h or 48 h, respectively. HMECs were also seeded onto the luminal surfaces of two heparin-coated decellularized grafts for 3 h. One graft was placed in a perfusion culture system and cultured for an additional 6 h with flow and pressure. After culturing, there were 4.7 +/- 1.4 cells/mm(2) HMECs on control grafts and 11.4 +/- 1.4 cells/mm(2) in bFGF treated grafts (P < 0.05). Likewise, with CEPCs, there were 14.8 +/- 4.8 cells/mm(2) in control grafts and 33.3 +/- 7.3 cells/mm(2) in bFGF treated grafts. After only 3 h of cell attachment, 60% of HMECs were retained in the intact graft exposed flow relative to the static control graft, which is an acceptable level. These data demonstrate that bFGF coating on the heparin bound decellularized grafts significantly increases both HMEC and dog EPC proliferation and that seeded cells are stable under perfusion conditions.

Animals↗
PubMed2004

Clinical use and molecular mechanisms of action of extract of Ginkgo biloba leaves in cardiovascular diseases.

Ginkgo biloba is one of the oldest living tree species that has been referred to as a living fossil. Extract from Ginkgo biloba leaves (GBE) is among the most commonly used herbal drugs and is popularized for its alleged tonic effect and possible curative and restorative properties. There is an increasing evidence of the potential role of GBE in treating cardiovascular diseases. We examined the history of GBE usage and reviewed the literature on its effects on the cardiovascular system. In the extensive studies involving cell cultures and animal models, GBE has been shown to exert its action through diverse mechanisms. GBE has been reported to have antioxidatant properties, to modify vasomotor function, to reduce adhesion of blood cells to endothelium, to inhibit activation of platelets and smooth muscle cells, to affect ion channels, and to alter signal transduction. In addition, relevant clinical trials with CBE are being carried out, particularly in the treatment of arterial and venous insufficiency and in the prevention of thrombosis. Finally, the controversial clinical findings and the possible adverse interactions between GBE and other drugs are discussed. This review underscores the potential benefits of Ginkgo biloba in cardiovascular diseases, highlights the gaps in our current research, and suggests the necessity for more rigorous systematic investigation of cardiovascular properties of CBE.

Animals↗
PubMed2003

Reversal of transjugular intrahepatic portosystemic shunt (TIPS)-induced hepatic encephalopathy using a strictured self-expanding covered stent.

Hepatic encephalopathy is a known complication following percutaneous transjugular intrahepatic portosystemic shunt (TIPS) placement. We describe herein a simple and effective strategy of TIPS revision by creating an intraluminal stricture within a self-expanding covered stent, which is deployed in the portosystemic shunt to reduce the TIPS blood flow. This technique was successful in reversing a TIPS-induced hepatic encephalopathy in our patient.

Hepatic Encephalopathy↗
PubMed2003

Carotid artery stenting in a community setting: experience outside of a clinical trial.

Carotid artery angioplasty and stenting (CAS) currently represents a less invasive percutaneous alternative to conventional endarterectomy for the treatment of carotid occlusive disease. We report here the results and complication rates of CAS performed by a team of interventionalists at a non-clinical trial center utilizing a standardized CAS protocol. CAS was attempted in 51 arteries in 48 patients (mean age 71 +/- 9 years, range 53-90). Fifteen (29%) of 48 patients were symptomatic. Indications for CAS were previous ipsilateral endarterectomy (15/51, 29%), previous neck radiation therapy (1/51, 2%), or significant coronary artery disease (30/51, 59%). SMART((R)) stents were deployed via percutaneous femoral artery access, with anticoagulation (heparin, abciximab, aspirin, clopidogrel) and temporary transvenous cardiac pacemakers employed in all patients. Neuroprotection was not used. Neurological examination and duplex scans were performed in follow-up. CAS was successfully performed in 96% of cases (49 lesions/46 patients) with angiographic stenoses of 88 +/- 8%. Neurological complications included one (2%) minor stroke that occurred 12 hr after CAS. There were no periprocedural mortalities. Clinically significant bradycardia or asystole occurred in 11/49 (22%) procedures, necessitating short-term ventricular pacing. All stented vessels remained patent during 12.2 +/- 10.1 (range 1-37) months follow-up period. One asymptomatic restenosis (>70%) occurred at 3 months, which was successfully reangioplastied; we thus had 1-year angiographic restenosis rate of 2%. Patients selected for CAS may represent a subset of patients with carotid disease who have considerable comorbidities or unfavorable anatomy compared to those undergoing conventional endarterectomy. CAS may be performed safely outside of a clinical trial with results similar to those of published series from trial centers using a standardized protocol.

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