Remodeling and suppression of intimal hyperplasia of vascular grafts with a distal arteriovenous fistula in a rat model.

PURPOSE: The purpose of this study was to evaluate the effects of a distal arteriovenous fistula (dAVF) on the morphologic changes occurring in arterial bypass grafts by the use of a novel experimental model. METHODS: Aortofemoral bypass grafts with or without dAVFs were constructed in 36 Sprague-Dawley rats with a microsurgical technique. The bypass graft material consisted of deendothelialized autogenous tail artery (length, 25 mm; inside diameter, 0.5 mm). In 18 rats, dAVFs were constructed at the distal anastomosis. After 6 weeks, flow rates and shear stress were determined, and grafts were then harvested. Luminal, intimal, and medial cross-sectional areas were measured with computer imaging. Desmin, alpha-smooth muscle actin, and von Willebrand factor (vWF) were identified with immunohistochemistry. Endothelialization was evaluated with SEM. RESULTS: All bypass grafts remained patent at the time of graft harvest. Grafts with dAVFs showed increased flow rates (11.5 +/- 0.6 mL/min) compared with grafts without dAVFs (2.1 +/- 0.3 mL/min; P < .01). Shear stress was also increased in the dAVF group (340.9 +/- 23.4 dyne/cm(2) vs 113.7 +/- 12.5 dyne/cm(2); P < .01), with a corresponding suppression of intimal hyperplasia (0.059 +/- 0.011 mm(2) for dAVF grafts vs 0.225 +/- 0.009 mm(2) for non-dAVF grafts; P < .01). Staining for vWF was found in both the reendothelialized flow surface and the neointimal extracellular matrix. Remodeling of the grafts was characterized by a 50% increased luminal area, 70% decreased intimal area, and a 25% decreased medial area when a dAVF was constructed. CONCLUSION: A small animal experimental model of an arterial bypass graft can enable the evaluation of a variety of factors that influence graft patency. Increased blood flow velocity and shear stress induced by a dAVF are associated with a decrease in intimal and medial areas, which may reflect changes in cell proliferation, apoptosis, migration, or matrix deposition. Deposition of vWF was also found both in the endothelium and throughout the hyperplastic intima. These findings suggest that the hemodynamic and morphologic changes associated with dAVF may potentiate graft patency and function.

Absence of the brachial artery: report of a rare human variation and review of upper extremity arterial anomalies.

Variations in the arterial anatomy of the upper extremities, although uncommon, occur in up to one in five patients. Most of these variants occur in either the radial or ulnar artery; brachial artery variations are less common. The case we report is a rare anomaly consisting of brachial artery agenesis or regression. The brachial artery was absent from its origin but reconstituted as a normal-appearing vessel 3 cm above the antecubital fossa. The profunda brachii artery and the superior and inferior ulnar collateral arteries were also absent in this patient. The axillary artery served as the main collateral to the forearm. This constellation of anomalies has not been previously described or explained by developmental models in humans and other primates. We speculate that failure of development or arrest of specific vascular anlage in the upper extremity occurs at particular embryological stages because of unknown factors.

Endovascular treatment of mycotic hepatic artery aneurysm in the hostile abdomen--a case report.

Mycotic hepatic artery aneurysms are rare. This report documents a case in which a mycotic hepatic artery aneurysm was associated with Crohn's disease, renal adenocarcinoma, and a urinary tract infection. Endovascular management of this mycotic hepatic artery aneurysm was successful in the setting of a hostile abdomen based on multiple previous operations, a stoma, and a scarred abdomen.

The tourniquet revisited as an adjunct to lower limb revascularization.

PURPOSE: The purpose of this study was to evaluate the role and efficacy of the tourniquet in lower limb revascularization. METHODS: During a 3-year period, 195 patients underwent 205 infrainguinal reconstruction operations in the lower extremity. These patients underwent bypass with a tourniquet and inflow occlusion (group 1) or bypass without a tourniquet (group 2). The type of infrainguinal reconstruction, tourniquet ischemia time, blood loss, and complications related to tourniquet use were recorded. A subset of patients underwent serial muscle biopsies. Specimens from calf muscle were taken just (1) before application of the tourniquet, (2) before tourniquet release, and (3) once wound closure was initiated. These biopsy specimens were studied by histochemical staining and also analyzed for phosphorylase enzyme, a marker for subcellular ischemia. RESULTS: One hundred eleven patients underwent 117 infrainguinal reconstruction procedures in which the tourniquet and inflow occlusion were used. These patients were matched against 84 patients who underwent 88 infrainguinal reconstructions without the use of the tourniquet. Complete hemostatic control in group 1 was obtained in 108 of the procedures (92%). Eight percent of the procedures required minor additional techniques to obtain complete hemostasis; in two instances, the tourniquet was removed because it did not provide hemostasis. Mean tourniquet time was less than 1 hour for all reconstruction groups. There were no instances of neurologic deficit, thrombosis of distal vessels, or vascular injury that was related to the use of a tourniquet. A comparison of the two groups revealed no differences with regard to overall blood loss (P =.63) or duration of operation (P = 0.60), observations that reflect the complexity of the cases rather than the use or nonuse of a tourniquet. When tourniquet control was used, we noted a definite decrease in the time for the distal dissection, because total vascular control with extensive dissection was unnecessary. Histochemical analysis with phosphorylase revealed a conversion of tissue with active enzyme activity to a low level with tourniquet use (P <.05). CONCLUSION: The use of a tourniquet for lower limb revascularization is safe and effective and improves visualization of the operative field. Less dissection of the target vessels is required. With a combination of the nonuse of clamps and other occluding devices, we project a decrease in host hyperplastic response that will, in turn, impact favorably on patency rates. The possibility exists that early failure may be prevented by avoiding the application of traumatic forces to diseased and brittle or calcified arteries. In this study, tourniquet time had no impact on overall operative procedural time, although certain phases of the operation were clearly shortened and facilitated, particularly in complex and difficult reconstructions. Histochemical changes found in muscle biopsy specimens did not adversely impact patients clinically, but further investigation is required to elucidate subcellular events.

The tourniquet as a routine adjunct in lower limb revascularization.

The use of a tourniquet as an adjunct for lower limb revascularization is safe, effective and improves visualization of the operative field. Less dissection of the target vessels is required and combined with non-use of clamps and other occluding devices, we project a decrease in host hyperplastic response that will in turn impact favorably on patency rates. The possibility also exists that early failure may be prevented by avoiding application of traumatic forces to diseased and brittle or calcified arteries. Although tourniquet time may have no impact on overall operative procedural time, certain phases of the operation are clearly shortened and facilitated, particularly in complex and difficult reconstructions. Histochemical changes in muscle biopsies do not adversely impact on patients in a clinical sense, but further investigation is required to elucidate subcellular events.

History of prosthetic grafts.

The evolution of vascular surgery during the past five decades has established what was once controversial to be mandate, what was never dreamed of as debatable, and the vast body of knowledge yet to be unraveled--but requiring clinical application--as currently controversial. Controversy results when dissimilar therapies yield comparable outcomes, despite having been reached by different pathways. Scientific methods to dissect the precise mechanisms of cause/effect, and not reliance on associations, are necessary to resolve controversies that may contribute to inappropriate conclusions. Much effort has been expended by vascular surgeons in the search for an ideal vascular conduit. This edition of Seminars explores the status, past, present, and future, of a variety of graft materials. Future modifications and availability of the "ideal graft" will evolve as challenges are met.

Biological vascular grafts.

Biological bypass graft material has been used as an alternative to autogenous vein since the first lower extremity revascularization procedures were performed. Both immunogenicity and biodegradation can contribute to the failure of these grafts and must be addressed. Cryopreservation at ultralow temperatures (-196 degrees C) after pretreatment with dimethylsulfoxide has been successful in preserving viable vein graft endothelium. Both rejection and deterioration of the cellular elements may contribute to the relatively high failure rates. The umbilical vein graft has become an effective alternative to autogenous material. The glutaraldehyde tanning procedure increases tensile strength, masks antigenicity, and sterilizes the tissue. Recent results with excellent 5-year patency (67%) and cumulative limb salvage (80%) confirm the utility of this graft.

Effect of alpha-tocopherol, taurine and selenium on the attenuation of ischemia/reperfusion injury of splanchnic organs.

BACKGROUND: Splanchnic artery occlusion shock is caused by increased capillary permeability and cellular injury precipitated by oxygen derived free radicals following ischemia and reperfusion of splanchnic organs. The purpose of this study was to assess the role of several well-known oxygen-derived free radical scavengers in ameliorating or preventing this syndrome. STUDY DESIGN: Anesthetized rats were subjected to periods of occlusion of the visceral arteries and reperfusion. Tocopherol, taurine, selenium or a 'cocktail' of these three agents was injected subcutaneously for 4 consecutive days prior to operation. Mean arterial blood pressure was measured throughout the experimental period. Fluorometry and technetium-99m pyrophosphate counting of the visceral organs were performed as well as a histologic grading system for intestinal viability. RESULTS: Final mean arterial blood pressure associated with the 'cocktail' and selenium groups was 79.1 +/- 27.4 mmHg and 83.6 +/- 17.8 mmHg, respectively. These values were significantly higher than the control group, 40.8 +/- 11.4 mmHg (P < 0.05). Similar patterns of the benefit of selenium in contrast with the other groups were obtained with fluorescein perfusion, radioisotopic activity and histologic analysis. CONCLUSION: Pretreatment with selenium of splanchnic ischemia and reperfusion in the rat improves mean arterial blood pressure and microcirculatory visceral perfusion. Further analysis of the precise protective mechanism of selenium for reperfusion injury will enable visceral organs to withstand the consequences of increased capillary leakage and oxidant injury.

Clinical experience with everted cervical vein as patch material after carotid endarterectomy.

PURPOSE: The aim of this study was to evaluate the clinical efficacy of everted cervical veins used as patches after carotid endarterectomy. METHODS: A prospective nonrandomized comparative analysis was performed on patients with either everted cervical veins or saphenous veins as patches after carotid endarterectomy. Two hundred ninety-six patients underwent 329 carotid endarterectomies during an 8 1/2-year period (1987 to 1995). Saphenous vein patches were used in 125 (38%) cases and everted cervical veins in 167 (51%). These two groups were compared clinically and by sonographic surveillance. The mean follow-up of patients in this study was 27 +/- 11 months. RESULTS: No significant differences were noted regarding postoperative morbid events between the everted cervical and saphenous vein patch groups. Even at 5 years the percentage of patients without stroke for both groups exceeded 95%. Duplex surveillance studies also showed comparable percentages of recurrent moderate (50% to 69%) and severe (70% to 99%) stenosis, 5.6% and 6.9%, respectively, for everted cervical vein and 5.4% and 6.5%, respectively, for saphenous vein. Cumulative recurrent stenosis-free rates at 5 and 6 years exceeded 82% for each of the patch study groups. CONCLUSIONS: Based on the results of this study everted cervical veins are useful adjuncts to carotid endarterectomy, when patch angioplasty is necessary or desirable. Their performance is comparable to that of saphenous veins. Cervical veins are usually available, even when the saphenous vein is absent or inadequate. In addition, good saphenous veins can be spared and lower extremity excisions avoided.

Femorocaval bypass with femoral crossover bypass for iliofemoral and caval occlusion.

Progress in the management of major venous obstruction has lagged far behind advances in arterial reconstruction. As a result, literature reports consist of small numbers of patients, and most vascular surgeons have little or no experience in performing bypass procedures for major venous obstruction. In this setting, individual reports add to our cumulative knowledge in treating this disease. We therefore present our experience in the management of a patient with extensive bilateral femoropopliteal, iliac, and vena caval occlusion.

The milk rejection sign: a natural tumor marker.

Early discovery of breast cancer in the lactating female will result in improved survival rates. One such marker is the "milk rejection sign," which has rarely been described and consists of the rejection by the nursing infant of the lactating breast that harbors an occult breast carcinoma. Recognition of this particular sign is vital and will enable early diagnosis and improved prognosis.