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Biomedical subjects

T Schmitz-Rixen

Publications and source records attributed to T Schmitz-Rixen.

48 records · Page 3Linked to original sources
PubMed1988

Immunosuppressive treatment of aortic allografts.

Immunosuppression with cyclosporine (CsA) was explored as a means of preventing arterial allograft rejection and failure. Aortic allografts across the major histocompatibility barrier were studied in Brown-Norway and Lewis inbred rats. Grafts 1 cm long were interposed into the infra-abdominal aorta of Lewis recipients; five groups included two groups of untreated isograft and allograft control animals and three groups had allograft-CsA treatment regimens. The grafts were examined at 30, 60, and 100 days for patency, aneurysmal dilation, gross structural changes, inflammatory responses, and infiltration of W3/25- and OX8-positive lymphocytes. Only three allograft controls became occluded; the rest showed significant dilation (p less than 0.01), medial thinning and necrosis, intimal proliferation, and prominent cellular infiltration at 30 days. With all CsA regimens, aneurysmal dilation was significantly reduced or prevented (p less than 0.01), correlating with medial smooth muscle cell preservation. Cellular infiltration was delayed by an average daily dose of 5 to 10 mg/kg subcutaneous CsA for 30 days and was suppressed at 100 days by a continuous 5 mg/kg dose every 4 days. Intimal thickening in the graft was delayed but not prevented. We conclude that a low maintenance dose of CsA provides effective immunosuppression, thereby preventing aneurysm formation, and that the potential use of arterial allografts in vascular surgery may need to be readdressed.

Animals↗
PubMed1985

[Early morbidity and fatality following carotid disobliteration].

At the University Hospital of Cologne-Lindenthal 260 patients underwent carotid endarterectomy during a period of 10 years. 9 patients died, representing an operative mortality rate of 2.9%. 80% of our patients with an acute stroke died. We see no indication for surgery in acute stroke. Postoperatively, 20 patients had a neurologic deficit, transient deficits occurred in 3,6% (11 patients) permanent deficits in 3% (9 patients). Carotid endarterectomy may be complicated by cranial nerve damage. The importance of these injuries is evident if bilateral carotid endarterectomy is being considered.

Carotid Artery Diseases↗
PubMed1984

[Blood vessel wall regeneration in the use of a new monofilament, resorbable suture material for arterial anastomoses].

A new synthetic, absorbable suture has been tested on 15 mongrel dogs. A total of 132 simple end-to-end anastomoses has been performed in common carotid, iliac and femoral arteries and the aorta abdominalis with monofilament, absorbable polydioxanon. Aneurysms or infections did not occur. The patency rate up to 250 days was 98.5%. All vessels were studied by angiography and light- or electron-microscopy. The new monofilament suture material is characterized by extended absorption time and low foreign body reaction. It leads more rapidly to the restitution of the vascular wall than nonabsorbable sutures.

Arteries↗
PubMed1984

Angiosarcoma in primary lymphedema of the lower extremity--Stewart-Treves syndrome.

After a 20-year latent period an angiosarcoma developed in the edematous leg of a 74-year-old woman with primary lymphedema. A deep venous thrombosis of the leg which further aggravated tissue swelling preceded the appearance of angiosarcoma. Histogenetic classification of the tumor as hemangiosarcoma rather than lymphangiosarcoma was favored by positive immunohistochemical staining for Factor VIII. Despite high amputation and isolated perfusion with hyperthermal cytostatic infusion, she developed local recurrence and distant metastases and died 16 months after operation. Patients with chronic primary or secondary lymphedema are susceptible to angiosarcoma although the overall risk is small.

Aged↗
PubMedDate not supplied

Arteriogenesis versus angiogenesis: similarities and differences.

Cardiovascular diseases account for more than half of total mortality before the age of 75 in industrialized countries. To develop therapies promoting the compensatory growth of blood vessels could be superior to palliative surgical interventions. Therefore, much effort has been put into investigating underlying mechanisms. Depending on the initial trigger, growth of blood vessels in adult organisms proceeds via two major processes, angiogenesis and arteriogenesis. While angiogenesis is induced by hypoxia and results in new capillaries, arteriogenesis is induced by physical forces, most importantly fluid shear stress. Consequently, chronically elevated fluid shear stress was found to be the strongest trigger under experimental conditions. Arteriogenesis describes the remodelling of pre-existing arterio-arteriolar anastomoses to completely developed and functional arteries. In both growth processes, enlargement of vascular wall structures was proposed to be covered by proliferation of existing wall cells. Recently, increasing evidence emerges, implicating a pivotal role for circulating cells, above all blood monocytes, in vascular growth processes. Since it has been shown that monocytes/ macrophage release a cocktail of chemokines, growth factors and proteases involved in vascular growth, their contribution seems to be of a paracrine fashion. A similar role is currently discussed for various populations of bone-marrow derived stem cells and endothelial progenitors. In contrast, the initial hypothesis that these cells -after undergoing a (trans-)differentiation- contribute by a structural integration into the growing vessel wall, is increasingly challenged.

Animals↗
PubMedDate not supplied

Does vascular stapling improve compliance of vascular anastomoses?

Elastic properties of vessel walls are altered by vascular anastomoses. Such alterations may lead to neointimal hyperplasia, which is a common cause of reocclusion following vascular surgery. The severity of paraanastomotic hypercompliant zones and anastomotic compliance drop depend on suturing material and on elastic properties of the anastomotic vessel segments. This study compares paraanastomotic hypercompliance and anastomotic compliance drop when using a new vascular closure system (VCS) and a conventional, continuous suture line in the preparation of end-to-end anastomoses. Compliance of artery-artery, vein-artery, and polytetrafluoroethylene-artery anastomoses was measured in an artificial circulation system at mean pressures of 60, 90, and 120 mm Hg, comparing conventional suturing and the VCS. When using the VCS for vein-artery anastomoses, significantly less postanastomotic hypercompliance was achieved at mean pressures of 60 mm Hg (14.2 +/-3.8% above remote postanastomotic area), compared to suture (55.1 +/-14.8%, p<0.05). At 90 mm Hg, respective values were 11.0 +/-2.3% for VCS and 54.7 +/-10.1% for suture, p<0.01. At 120 mm Hg, in polytetrafluoroethylene-artery anastomoses, the anastomotic compliance drop was significantly less when using the continuous suture line (93.9 +/-1.1% below remote postanastomotic compliance), compared to VCS (97.2 +/-0.2%, p<0.05). Compared to conventional suturing, use of the VCS reduced postanastomotic hypercompliance in vein-artery anastomoses.

Anastomosis, Surgical↗
PubMedDate not supplied

[Carotid stenosis surgery: results after 10 years' experience].

From 1973 to July 1983 220 patients at the University clinic of Cologne, Germany, had carotid endarterectomies for carotid stenosis. A shunt has always been used. The procedure mortality and morbidity were 3,4% and 6,3% respectively. We do not see any indication to operate in acute stroke.

Arterial Occlusive Diseases↗
PubMedDate not supplied

[Compliance: a fundamental biomechanical property in the maintenance of an arterial reconstruction?].

The widespread use of graft replacement material led to complications inherent to these prostheses with increasing frequency. The discussion is still open on identifying those inherent features of vascular grafting that could contribute to long term success or short term failure. The search has been prompted for better arterial substitutes, among others, for repair particularly of lesions of smaller arteries. The ideal graft should have an innately blood-compatible flow surface with fixed endothelium and basement membrane and innately physiological mechanical properties. There are a number of biological and plastic materials competing for this goals. All plastic materials studied in clinical trials so far stimulate an uncontrollable proliferative response in host arteries behind or in the distal anastomosis; such causes failure of grafts when of small caliber. This distal anastomotic subintimal hyperplasia (SIH) is an ubiquitous pathologic entity in late graft occlusion. The cause of SIH has been the subject of much investigation. The role of compliance mismatch between host artery and vascular grafts in the development of SIH is discussed in this paper. While compliance may, in fact, be an important parameter in determining the results of bypass grafting, the dominant influence of hemodynamic and thrombogenic factors has continued to mask what is probably a very subtle effect. Summarizing the current knowledge it is likely that match or mismatch between the anisotropic behavior of the host artery and the linear respectively nonlinear response to varying blood pressure of the graft influences patency results. Any mismatch in tubular compliance in a quantitative manner will contribute to the long-term results but in a lesser degree. Disturbance of the biomechanical properties of the arterial tree due to an vascular anastomosis seems to be of utmost importance to the outcome, but up to now we were not able to demonstrate a link conclusively between compliance mismatch and the occurrence of subintimal hyperplasia. The present results imply a major impact on future graft design and the development of better anastomotic techniques, because compliance is a critical parameter for maintenance of arterial reconstructions.

Anastomosis, Surgical↗