Francis J. Prendergast

A review of the proliferative behaviour, morphology and phenotypes of vascular smooth muscle

This article reviews the proliferative, structural and synthetic behaviour of vascular smooth muscle cells under a variety of conditions. It shows how some experimental procedures produce dramatic increases in smooth muscle cell proliferation and, in many cases, subsequent cell migration to the intimal layer. Possible control mechanisms influencing changes in such activity are discussed. The morphology, histogenesis and differentiation of vascular smooth muscle is reviewed, with particular emphasis on the differentiation of such cells into contractile or synthetic phenotypes. The significance of the synthetic phenotype is discussed in relation to the synthesis of intra- and extracellular components.

Vein to artery grafts. A quantitative study of revascularization by vasa vasorum and its relationship to intimal hyperplasia.

Iliolumbar vein to iliac artery grafts were placed in 40 rats by microsurgical technique. Groups of animals were perfused with fixative at eight intervals between one and 20 weeks after operation, and sections of the graft and control arteries (the opposite iliacs) were analyzed microscopically. The revascularization of the graft by capillaries commenced within the first postoperative week. The level of vascularity (capillaries per cross-sectional mm2) increased during the first four weeks, maintained a constant level and declined after week 16. The grafts of the 17--20 week group were substantially less vascular than the earlier groups. Intimal thickening commenced at three to four weeks after operation, i.e. during the period of increasing graft vascularity. The mean intimal proportion of the graft was 14% at four to five weeks and at 17--20 weeks was 35% of the cross-sectional area of the graft wall. However, the actual thickness of the intima did not increase significantly with time, rather the whole graft wall tended to become thinner. At 17--20 weeks grafts which showed a high degree of intimal thickening had significantly fewer capillaries within their walls. Quantitative evidence is presented to suggest that the continued growth of the graft intima may not be supported by a similar increase in the number of vasa vasorum. Therefore, it is suggested that the reduced level of vascularity in grafts with hyperplastic intimae may form an ischemic basis for degenerative changes which are known to take place in some long-term grafts.

The Perth HLB Bifurcated Endoluminal Graft: A Review of the Experience and Intermediate Results

Endoluminal grafting for abdominal aortic aneurysm based upon Dacron-coated Z stents was commenced in March 1993. A modular system for treatment of infrarenal aorto-iliac aneurysmal disease was developed in 1994. The experimental model, method of delivery, graft construction and initial results were reported. Since 1994, 108 bifurcated HLB (Perth) endografts for infrarenal aorto-iliac aneurysmal disease have been implemented. Initial technical success in deployment and exclusion of the aneurysm was achieved in 94 (87%) cases. Secondary endovascular procedures were performed in six cases and were successful in excluding the aneurysm. Ninety patients are alive currently. Twelve have died of co-morbid conditions. Six have died of aneurysmal disease, either from rupture or the result of treatment attempts. Fifteen early endoleaks (within 30 days) have been detected with three persisting. Four have sealed without further intervention, six after the secondary procedure and two patients have died. Conversion to open aneurysmal repair has been performed in five cases: three early and two late. Two of the early group but none of the late intervention group died. No graft infections have been detected to date. With increasing experience criteria for patient selection for endoluminal grafting and the type of graft to be inserted, have been developed. These criteria, lessons learnt and technical points of importance are discussed.

Duration of antimicrobial prophylaxis in vascular surgery

BACKGROUND This randomized clinical trial compares the incidence of wound infection after vascular surgery in patients who received prophylaxis using the same antibiotic as either a single-dose or a multiple-dose regimen (until the lines/drain tubes were removed, but not for more than 5 days). METHODS Each of the 302 patients who entered the study received ticarcillin 3.0 g/clavulanate 0.1 g (Timentin) intravenously immediately after the induction of anesthesia. Patients randomized to the multiple-dose group received an average of 14.3 doses (range 9 to 20). RESULTS The incidence of wound infections was 18% (28 of 153) for patients in the single-dose group and 10% (15 of 149) for patients in the multiple-dose group (P = 0.04; relative risk estimate = 2.00, 95% confidence interval = -1.02 to 3.92). CONCLUSIONS A multiple-dose antibiotic regimen, rather than single-dose therapy, provides optimal prophylaxis against wound infection for patients undergoing vascular surgery.

Vein to artery grafts. An experimental study of reinnervation of the graft wall.

Iliolumbar vein to iliac artery grafts were placed in 21 rats by microsurgical techniques. Graft innervation was examined at five time intervals between 1 and 32 weeks after surgery. Nerve fibers were demonstrated microscopically by formaldehyde-induced fluorescence of catecholamines. The morphology and degree of graft innervation were assessed, semiquantitatively, relative to the contralateral iliac artery (control) within each animal. Nerves were seen in the graft region as early as 2 weeks, but it was not until 4 weeks that they were present along its length (5 mm). The formation of a nerve plexus in the adventitia surrounding the graft was evident at 8 weeks. By 16 weeks the degree of innervation in the graft had increased to a level that was greater than the control iliac artery in three of four animals examined. Grafts at 32 weeks were also hyperinnervated. However, the morphology of this innervation was different from the control arteries; nerve fibers were finer, not varicosed, and were located at a greater distance from the outer layer of smooth muscle cells. The origin of the nerves appeared to be collateral sprouts from nerves supplying the adjacent iliac vein and also from invading vasa vasorum. The host iliac artery nerve plexus did not contribute to graft innervation.

Endovascular Conversion Procedure for Failed Primary Endovascular Aortic Stent-Grafts

Initial failure of successful deployment of endovascular aortic stent-grafts can be due to a variety of factors and frequently requires surgical intervention. We describe an endovascular technique for salvaging initially failed tubular aortic and bifurcated aortoiliac stent-grafts with reference to three cases.