J.H. van Bockel

Endoleakage after stent-graft treatment of abdominal aneurysm: Implications on pressure and imaging—an in vitro study

BACKGROUND Endoleakage is a fairly common problem after endovascular repair of abdominal aortic aneurysm and may prevent successful exclusion of the aneurysm. The consequences of endoleakage in terms of pressure in the aneurysmal sac are not exactly known. Moreover, the diagnosis of endoleakage is a problem because visualization of endoleaks can be difficult. METHOD With an ex vivo model of circulation with an artificial aneurysm managed by means of a tube graft, studies were performed to evaluate precisely known diameters of endoleaks with both imaging techniques (computed tomography and digital subtraction angiography) and pressure measurements of the aneurysmal sac. The experiments were performed without endoleak (controls) and with 1.231-French (0.410 mm), 3-French (1 mm), and 7-French (2.33 mm) endoleaks. Pressure and imaging were evaluated in the absence and presence of a simulated open lumbar artery. The pressure in the prosthesis and in the aneurysmal sac were recorded simultaneously. Digital subtraction angiography with and without a Lucite acrylic plate, computed tomographic angiography, and delayed computed tomographic angiography were performed. For the first experiments, the aneurysmal sac was filled with starch solution. All tests were repeated with fresh thrombus in the aneurysmal sac. RESULTS Each endoleak was associated with a diastolic pressure in the aneurysmal sac that was identical to diastolic systemic pressure, although the pressure curve was damped. At digital subtraction angiography without a Lucite acrylic plate, the 1.231-French (0.410 mm) endoleak was visualized without an open lumbar artery. When a Lucite acrylic plate was added, the endoleak was not visible until a lumbar artery was opened. In the presence of thrombus within the aneurysmal sac, all endoleaks were not visualized at digital subtraction angiography. At computed tomographic angiography, all endoleaks were not visualized in the absence of a thrombus mass in the aneurysmal sac. In the presence of thrombus within the aneurysmal sac, the 1.231-French (0.410 mm) endoleak became visible after opening of a simulated lumbar artery. At delayed computed tomographic angiography, all endoleaks were visualized without and with thrombus. CONCLUSION Every endoleak, even a very small one, caused pressure greater than systemic diastolic pressure within the aneurysmal sac. However, small endoleaks were not visualized with digital subtraction angiography and computed tomographic angiography, whereas all endoleaks were visualized with a delayed computed tomographic angiography protocol. We believe that follow-up examinations after stent graft placement for aortic aneurysms should focus on pressure measurements, but until this is clinically feasible, delayed computed tomographic angiography should be performed.

Anti–MCP-1 Gene Therapy Inhibits Vascular Smooth Muscle Cells Proliferation and Attenuates Vein Graft Thickening Both In Vitro and In Vivo

Objective—Because late vein graft failure is caused by intimal hyperplasia (IH) and accelerated atherosclerosis, and these processes are thought to be inflammation driven, influx of monocytes is one of the first phenomena seen in IH, we would like to provide direct evidence for a role of the MCP-1 pathway in the development of vein graft disease. Methods and Results—MCP-1 expression is demonstrated in various stages of vein graft disease in a murine model in which venous interpositions are placed in the carotid arteries of hypercholesterolemic ApoE3Leiden mice and in cultured human saphenous vein (HSV) segments in which IH occurs. The functional involvement of MCP-1 in vein graft remodeling is demonstrated by blocking the MCP-1 receptor CCR-2 using 7ND-MCP-1. 7ND-MCP1 gene transfer resulted in 51% reduction in IH in the mouse model, when compared with controls. In HSV cultures neointima formation was inhibited by 53%. In addition, we demonstrate a direct inhibitory effect of 7ND-MCP-1 on the proliferation of smooth muscle cell (SMC) in HSV cultures and in SMC cell cultures. Conclusion—These data, for the first time, prove that MCP-1 has a pivotal role in vein graft thickening due to intimal hyperplasia and accelerated atherosclerosis.

Natural Killer Cells and CD4 + T-Cells Modulate Collateral Artery Development

Objective—The immune system is thought to play a crucial role in regulating collateral circulation (arteriogenesis), a vital compensatory mechanism in patients with arterial obstructive disease. Here, we studied the role of lymphocytes in a murine model of hindlimb ischemia. Methods and Results—Lymphocytes, detected with markers for NK1.1, CD3, and CD4, invaded the collateral vessel wall. Arteriogenesis was impaired in C57BL/6 mice depleted for Natural Killer (NK)-cells by anti-NK1.1 antibodies and in NK-cell–deficient transgenic mice. Arteriogenesis was, however, unaffected in J&agr;281-knockout mice that lack NK1.1+ Natural Killer T (NKT)-cells, indicating that NK-cells, rather than NKT-cells, are involved in arteriogenesis. Furthermore, arteriogenesis was impaired in C57BL/6 mice depleted for CD4+ T-lymphocytes by anti-CD4 antibodies, and in major histocompatibility complex (MHC)-class-II–deficient mice that more selectively lack mature peripheral CD4+ T-lymphocytes. This impairment was even more profound in anti-NK1.1-treated MHC-class-II–deficient mice that lack both NK- and CD4+ T-lymphocytes. Finally, collateral growth was severely reduced in BALB/c as compared with C57BL/6 mice, 2 strains with different bias in immune responsiveness. Conclusions—These data show that both NK-cells and CD4+ T-cells modulate arteriogenesis. Promoting lymphocyte activation may represent a promising method to treat ischemic disease.

Ideals of patient autonomy in clinical decision making: a study on the development of a scale to assess patients’ and physicians’ views

Objectives: Evidence based patient choice seems based on a strong liberal individualist interpretation of patient autonomy; however, not all patients are in favour of such an interpretation. The authors wished to assess whether ideals of autonomy in clinical practice are more in accordance with alternative concepts of autonomy from the ethics literature. This paper describes the development of a questionnaire to assess such concepts of autonomy. Methods: A questionnaire, based on six moral concepts from the ethics literature, was sent to aneurysm patients and their surgeons. The structure of the questionnaire was assessed by factor analysis, and item reduction was based on reliability. Results: Ninety six patients and 58 surgeons participated. The questionnaire consisted of four scales. Two of the scales reflected the paternalistic and consumerist poles of the liberal individualist model, one scale reflected concepts of Socratic autonomy and of procedural independence, and the fourth scale reflected ideals of risk disclosure. Discussion: The Ideal Patient Autonomy Scale is a 14 item normative instrument. It is clearly distinct from the generally used psychological preference questionnaires that assess preferences for physician-patient roles.

Accelerated Atherosclerosis by Placement of a Perivascular Cuff and a Cholesterol-Rich Diet in ApoE*3Leiden Transgenic Mice

Intimal hyperplasia after vascular injury is usually studied in animal models with healthy, normocholesterolemic animals. Here, we assess the effect of diet-induced hypercholesterolemia on the induction of intimal hyperplasia in ApoE*3Leiden mice. A nonconstrictive polyethylene cuff was placed around the femoral artery of ApoE3*Leiden mice fed a highly cholesterol-rich diet, a mildly cholesterol-rich diet, or a chow diet for 4 weeks. Diets were continued after cuff placement until euthanization. At several time points (1 to 14 days), mice were euthanized and the intimal hyperplasia in the cuffed arteries was analyzed. In mice fed a chow diet, a 2- to 4-cell-layer-thick intima, predominantly consisting of alpha smooth muscle cell actin-positive cells, was observed after 14 days. A mildly cholesterol-rich diet (mean plasma-cholesterol level, 10.5 mmol/L) resulted in a 2.7-fold increase of total intimal area, and a highly cholesterol-rich diet (mean plasma cholesterol level 28. 6 mmol/L), in a 7.8-fold increase. In the high-cholesterol group, the intima consisted predominantly of lipid-loaded foam cells and alpha smooth muscle cell actin-positive cells. Foam cell accumulation could be observed by as early as 3 days, resulting in a near-total occlusion of the lumen after 14 days. Hypercholesterolemia resulted in a rapid, cholesterol-dependent induction of foam cell-rich intimal hyperplasia in cuffed femoral arteries of ApoE*3Leiden mice. In conclusion, the present data show that the combination of a local (cuff placement) and a systemic (hypercholesterolemic) risk factor of atherosclerosis results in a rapid induction (within 14 days) of atherosclerotic-like lesions in ApoE*3Leiden mice.

Increased local cytostatic drug exposure by isolated hepatic perfusion: a phase I clinical and pharmacologic evaluation of treatment with high dose melphalan in patients with colorectal cancer confined to the liver

A phase I dose-escalation study was performed to determine whether isolated hepatic perfusion (IHP) with melphalan (L-PAM) allows exposure of the liver to much higher drug concentrations than clinically achievable after systemic administration and leads to higher tumour concentrations of L-PAM. Twenty-four patients with colorectal cancer confined to the liver were treated with L-PAM dosages escalating from 0.5 to 4.0 mg kg–1. During all IHP procedures, leakage of perfusate was monitored. Duration of IHP was aimed at 60 min, but was shortened in eight cases as a result of leakage from the isolated circuit. From these, three patients developed WHO grade 3–4 leukopenia and two patients died due to sepsis. A reversible elevation of liver enzymes and bilirubin was seen in the majority of patients. Only one patient was treated with 4.0 mg kg–1L-PAM, who died 8 days after IHP as a result of multiple-organ failure. A statistically significant correlation was found between the dose of L-PAM, peak L-PAM concentrations in perfusate (R = 0.86, P≤ 0.001), perfusate area under the concentration-time curve (AUC; R = 0.82, P< 0.001), tumour tissue concentrations of L-PAM (R = 0.83, P = 0.011) and patient survival (R = 0.52, P = 0.02). The peak L-PAM concentration and AUC of L-PAM in perfusate at dose level 3.0 mg kg–1(n = 5) were respectively 35- and 13-fold higher than in the systemic circulation, and respectively 30- and 5-fold higher than reported for high dose oral L-PAM (80–157 mg m–2) and autologous bone marrow transplantation. Median survival after IHP (n = 21) was 19 months and the overall response rate was 29% (17 assessable patients; one complete and four partial remissions). Thus, the maximally tolerated dose of L-PAM delivered via IHP is approximately 3.0 mg kg–1, leading to high L-PAM concentrations at the target side. Because of the complexity of this treatment modality, IHP has at present no place in routine clinical practice.

Vascular Growth in Ischemic Limbs: A Review of Mechanisms and Possible Therapeutic Stimulation

Stimulation of vascular growth to treat limb ischemia is promising, and early results obtained from uncontrolled clinical trials using angiogenic agents, e.g., vascular endothelial growth factor, led to high expectations. However, negative results from recent placebo-controlled trials warrant further research. Here, current insights into mechanisms of vascular growth in the adult, in particular the role of angiogenic factors, the immune system, and bone marrow, were reviewed, together with modes of its therapeutic stimulation and results from recent clinical trials. Three concepts of vascular growth have been described to date-angiogenesis, vasculogenesis, and arteriogenesis (collateral artery growth)-which represent different aspects of an integrated process. Stimulation of arteriogenesis seems clinically most relevant and has most recently been attempted using autologous bone marrow transplantation with some beneficial results, although the mechanism of action is not completely understood. Better understanding of the highly complex molecular and cellular mechanisms of vascular growth may yet lead to meaningful clinical applications.

Complications of standard elective abdominal aortic aneurysm repair

OBJECTIVE To evaluate complications of standard elective repair of infrarenal abdominal aortic aneurysms. DESIGN Prospective multicentre study. MATERIALS Two-hundred and ninety-one consecutive patients undergoing standard elective surgery for an infrarenal aortic aneurysm. METHODS Recording adverse events according to the recommendations of the Ad Hoc Committee on Reporting Standards. RESULTS Seventy-five patients (26%) experienced some complication following elective aortic aneurysm surgery. Twenty-two patients had a mild complication (7.6%, 95% C.I. 4.8-11.2%), 27 a moderate (9.3%, 95% C.I. 6.2-13.2%) and 26 patients had a severe and/or fatal complication (8.9%, 95% C.I. 5.9-12.8%). The in-hospital mortality was 4.1% (12 patients, 95% C.I. 2.2-7.1%). Cardiac failure was the commonest primary cause for death (58%). Twenty-two per cent of the patients had a non-fatal complication: the most frequent being pulmonary (10%) and cardiac (10%). Patients with a history of cardiac events had a five times higher risk of a fatal outcome (95% C.I. 1.1-24.0) and a two and a half times higher risk of any severe fatal or non-fatal complication (95% C.I. 1.0-6.5). Other risk factors were advancing age and the presence of pulmonary disease. CONCLUSIONS In addition to mortality, morbidity figures of standard aneurysm operations are important, as well as associated risk factors. This is especially true when evaluating early repair of small aneurysms and new endovascular techniques.

Accelerated Atherosclerosis and Calcification in Vein Grafts: A Study in APOE*3 Leiden Transgenic Mice

Abstract— Vein grafts fail due to development of intimal hyperplasia and accelerated atherosclerosis. Many murine genetic models in which genes are overexpressed, deleted, or mutated have been introduced recently. Therefore, mouse models are very well suited to dissect the relative contribution of different genes in the development of accelerated atherosclerosis. In the present study, we evaluated whether accelerated atherosclerosis in human vein grafts could be mimicked in hypercholesterolemic APOE*3 Leiden transgenic mice. Venous bypass grafting was performed in the carotid artery in APOE*3 Leiden mice fed either a standard chow diet or a high cholesterol–rich diet for 4 weeks. At several time points (0 hour to 28 days), mice were euthanized and the morphology of the vein grafts was analyzed. In normocholesterolemic mice, vein graft thickening up to 10-fold original thickness, predominantly consisting of &agr;-smooth muscle cell actin–positive cells, was observed after 28 days. In hypercholesterolemic mice, accelerated atherosclerosis with accumulation of lipid-loaded foam cells was observed within 7 days after surgery. This accelerated atherosclerosis progressed in time and resulted in significant increase in vein graft thickening up to 50 times original thickness with foam cell–rich lesions and calcification within 28 days after surgery. The atherosclerotic lesions observed in these murine grafts show high morphological resemblance with the atherosclerotic lesions observed in human vein grafts. This accelerated, diet-dependent induction of atherosclerotic-like lesions in murine vein grafts provides a valuable tool in evaluating the mechanisms of accelerated atherosclerosis and therapeutic interventions of vein graft disease.

Inhibition of Complement Component C3 Reduces Vein Graft Atherosclerosis in Apolipoprotein E3–Leiden Transgenic Mice

Background— Venous bypass grafts may fail because of development of intimal hyperplasia and accelerated atherosclerosis. Inflammation plays a major role in these processes. Complement is an important part of the immune system and participates in the regulation of inflammation. The exact role of complement in the process of accelerated atherosclerosis of vein grafts has not yet been explored, however. Methods and Results— To assess the role of complement in the development of vein graft atherosclerosis, a mouse model, in which a venous interposition was placed in the common carotid artery, was used. In this model, vein graft thickening appeared within 4 weeks. The expression of complement components was studied with the use of immunohistochemistry on sections of the thickened vein graft. C1q, C3, C9, and the regulatory proteins CD59 and complement receptor-related gene y could be detected in the lesions 4 weeks after surgery. Quantitative mRNA analysis for C1q, C3, CD59, and complement receptor-related gene y revealed expression of these molecules in the thickened vein graft, whereas C9 did not show local mRNA expression. Furthermore, interference with C3 activation with complement receptor-related gene y–Ig was associated with reduced vein graft thickening, reduced C3 and C9 deposition, and reduced inflammation as assessed by analysis of influx of inflammatory cells, such as leukocytes, T cells, and monocytes. In addition, changes in apoptosis and proliferation were observed. When C3 was inhibited by cobra venom factor, a similar reduction in vein graft thickening was observed. Conclusions— The complement cascade is involved in vein graft thickening and may be a target for therapy in vein graft failure disease.