Transplantation of the entire small bowel in inbred rats using cyclosporine.

Inbred strains of rats were used to analyze unidirectional host-versus-graft disease (transplant rejection) without graft-versus-host disease in small intestinal transplants and the immunosuppressive properties of cyclosporine (CsA). Forty-six Lewis rats received heterotopic transplants of the entire small bowel in four groups: Lewis-to-Lewis isografts, without CsA; Lewis-to-Lewis isografts, with CsA (15 mg/kg/day); (Lewis X ACI)F1-to-Lewis allografts, without CsA; (Lewis X ACI)F1-to-Lewis allografts, with CsA. Small bowel rejection was associated with gross morphological changes that preceded all other findings. A histologic scoring system assessed the degree of transplant rejection. A characteristic transient weight loss was seen in animals rejecting their bowels. Glucose absorption was impaired and polyethylene glycol absorption increased during rejection. Cyclosporine inhibited all of these changes in allografted rats. It is concluded that daily administration of cyclosporine is effective in preventing the morphologic and functional changes of acute transplant rejection in intestinal allografts and does not change these parameters in transplants that are not rejecting.

Telemedicine and endovascular aortic grafting.

Endovascular aortic grafting represents a minimally invasive approach to aortic aneurysm repair. The technique requires a variety of new skills and extensive training. Telemedicine enhances mentoring and technical support for surgeons performing the technique.

Is proximal aortic neck dilatation after endovascular aneurysm exclusion a cause for concern?

PURPOSE: The purpose of this study was to evaluate the extent and frequency of dilatation of the proximal aortic neck over time after endovascular exclusion of abdominal aortic aneurysms and the effect on the continued integrity of the repair. METHODS: Patients enrolled in the multicenter tube and bifurcated trials of the Guidant-Endovascular Technologies Ancure endografting system and at least 1 year of follow-up were reviewed. Neck diameter measurements were obtained from computed tomography scans that were obtained with and without contrast by an independent core laboratory facility. The diameter was considered to be the minor axis of the first slice at which point at least one half of the proximal attachment frame was located. A change exceeding 2.5 mm was considered to be significant. RESULTS: At 1 year, 13% of the patients (42/314 patients) showed evidence of proximal neck dilatation, with a mean diameter increase of 4.8 +/- 2.4 mm. The proportion of patients with dilatation increased to 21% at 2 years (48/226 patients) and 19% at 3 years (11/59 patients). The initial presence of an endoleak, the neck length, and the aneurysm size had no clear effect on the development of neck enlargement. Initial neck diameter was inversely related to and the strongest predictor of later dilatation. Graft oversizing was not an independent predictor of neck dilatation on multivariate analysis. Only one migration of the proximal attachment system was observed during follow-up. CONCLUSION: Most proximal aortic necks remain stable, but approximately 20% of necks increase in diameter by 2 years. Smaller necks dilate more often than larger ones. This effect is independent from the frequent oversizing of grafts in smaller necks. The integrity of the repair remains good at 3 years of follow-up.

Reversed vein graft stenosis: early diagnosis and management.

Conscientious surveillance of intrainguinal bypass grafts is mandatory to detect vein graft stenoses, which, if uncorrected, can lead to graft occlusion. It is now widely accepted that noninvasive vascular laboratory studies are the best way to detect these lesions. However, controversy still exists over treatment, specifically whether balloon angioplasty is an acceptable substitute for surgery (patch angioplasty or short jump grafts) in the treatment of these lesions. We have always favored balloon angioplasty as primary treatment and have summarized our experience with treating 72 stenotic reversed femoropopliteal and femorotibial vein grafts, which represent 12% of 521 bypass grafts performed at our institution. Prosthetic and in situ grafts are specifically excluded from this report, as well as occluded grafts, found to have stenotic lesions after lytic therapy. The most common stenotic lesion occurred within 4 cm of the proximal anastomosis (29/72 = 40%). The other sites were near the distal anastomosis (7/72 = 10%), and in the middle of the graft (15/72 = 12%). Eighty-one percent (58/72) of the lesions were treated initially by balloon angioplasty with a 31% recurrence. Twenty-nine percent of the 14 grafts treated surgically by vein patch angioplasty or short jump grafts experienced recurrence. Overall 61% (44/72) of the stenotic grafts were treated by balloon angioplasty alone. The 5-year life-table assisted primary patency after correction of the stenotic lesion was 61%. The patency of the grafts from the time of initial bypass surgery, however, was 80%. Location of the stenosis within the graft was a major determinant of patency. Lesions in the proximal graft, proximal anastomosis, and distal graft taken as a group had significantly better patency than the midgraft and distal anastomotic lesions (5-year patency, 65% vs 48%, p less than 0.001 log rank test). We continue to recommend balloon angioplasty as primary therapy for vein graft stenosis except for those occurring in the midgraft and distal anastomosis. Fortunately, this group accounts for only 36% of lesions seen with reversed veins. Recurrent stenosis after balloon angioplasty should be repaired surgically.

Bifurcated endovascular grafting for abdominal aortic aneurysm.

Endovascular grafting represents a minimally invasive approach to prosthetic aortic grafting for abdominal aortic aneurysms (AAA). We reviewed our initial experience with a bifurcated endovascular graft that shares with conventional grafts the characteristics of discrete transaortic fixation and unitary unsupported woven polyester construction. Twenty-eight patients (26 male, 2 female; age: 58-93) with infrarenal aortic aneurysms between 41 and 82 mm in greatest diameter (x = 55.4 mm) underwent bifurcated endovascular grafting (Guidant/EVT, Menlo Park, CA) over an 18-month period. We concluded that bifurcated endovascular grafting with the EVT(R) device provides reliable and reproducible aneurysm exclusion with short hospital recovery and low morbidity.

Autologous superficial femoral vein for aortic reconstruction in infected fields.

Autogenous reconstruction is one option available for patients with aortic graft infection or mycotic aneurysms. We reviewed our recent institutional experience with all patients undergoing aortic reconstruction using autologous superficial femoral vein (SFV). Between February 1995 and November 1997, eight patients (five with prosthetic aortic graft infection and three with mycotic aneurysms, including one ruptured mycotic aneurysm) underwent single-stage aortic reconstruction using autologous SFV. Therapy for graft infection included graft excision and replacement with aortobifemoral or aortofemoral (with subsequent cross femoral) grafts fashioned from the SFV. The two patients undergoing elective repair of mycotic aneurysms were treated with extensive SFV patches, and the patient with a ruptured mycotic aneurysm underwent SFV tube grafting. Autogenous reconstruction of the aorta using the SFV in infected fields shows promise for salvage of life and limb during early experiences and short-term follow-up. Morbidity and mortality rates compare favorably with those from existing series, reconstruction is anatomic, and reinfection potential is low. Long-term follow-up and more extensive experience with this technique are needed to establish its role relative to other conventional methods.

Preliminary experience with the Endovascular Technologies bifurcated endovascular aortic prosthesis in a calf model.

PURPOSE: The purpose of this study was to develop a bifurcated endoluminal prosthesis for transfemoral placement in the aortoiliac position with a large-animal model that would simulate human implantation. METHODS: Fifteen calves (160 to 200 kg) underwent bilateral femoral artery exposure and transfemoral placement in the aortoiliac position of a bifurcated Dacron prosthesis, inserted through a 26F sheath with an over-the-bifurcation guide wire to retrieve the contralateral limb and secured proximally and distally with self-expanding attachment systems. The preferred location was determined before implantation and compared with final implant location by caliper measurements and angiography. Events during implantation, maneuvers used to accomplish accurate deployment, and final results, as judged by angiography and clinical evaluation, were recorded. Four animals survived and were used for chronic evaluation and healing by gross and microscopic studies. RESULTS: All grafts (n = 15) were patent at the end of the procedure. All (n = 7) noncrimped grafts had minor kinks in areas of curvature, whereas eight of eight crimped grafts (device modification) had none. Torque control of the body and individual limbs was necessary to correct twists before deployment in 10 of 15 grafts, with two greater than 30-degree twists remaining, which did not appear to affect flow. One implant was entirely deployed in the aorta because of parallax error, subsequently avoided by use of a marker board placed dorsally. Three premature deployments occurred, corrected by attachment system lock modification. The mean final implant position was within 2.9 +/- 1.4 mm (aortic), 1.6 +/- 1.1 mm, and 1.5 +/- 0.8 mm (contralateral and ipsilateral iliac limbs, respectively) of the intended position. Three of four animals intended for long-term evaluation were killed prematurely because of clinically evident spinal cord ischemia. Histologic sections at 2 weeks showed early wall repair without inflammatory cells and pannus ingrowth across the anastomosis. CONCLUSION: We conclude that implantation of a bifurcated endovascular prosthesis through the bilateral femoral approach is possible, provided the intended aortic implantation site (neck) is at least 12 mm in length (mean +/- 2 SD each direction). Torque control of each portion of the device will be needed in the majority of instances, with attention to parallax effect necessary for optimal placement. This animal model is not suitable for chronic graft evaluation because of its sensitivity for spinal cord ischemia. Healing data suggest graft incorporation similar to that of a surgically placed prosthesis.