Adamastor Humberto Pereira

Abdominal Aortic Aneurysm Treatment: Preliminary Results with the Talent Stent-Graft System

PURPOSE To evaluate the treatment of abdominal aortic aneurysm (AAA) with use of the endoluminal Talent stent-graft (TSG). PATIENTS AND METHODS In 10 men, AAA treatment was attempted with use of the TSG. All patients presented significant surgical risk, with chronic obstructive pulmonary disease and coronary arteriopathy. The mean age was 65.5 years (range, 57-82 years). The mean proximal neck diameter was 25.8 mm (range, 21.6-34 mm). Five of the TSGs were straight tubes and five were bifurcated systems. The main body of the TSG is made of a polyester graft material mounted on a self-expandable nitinol frame. The bifurcated system uses polytetrafluoroethylene (PTFE) material for the legs and extensions mounted on a self-expandable nitinol frame. The bifurcated grafts used a 22 to 27-F introducer and the extensions, a 18-F introducer through a surgical cutdown technique. RESULTS The TSG system was successfully implanted in nine patients and failed in one because of dislodgment after deployment, which required conversion to surgery. Four leaks occurred initially. One was sealed off with balloon dilation at the end of the procedure, one leak was treated with an additional extension, another leak disappeared spontaneously in 30 days, and the other leak required embolization 4 weeks after discharge. Seven patients were discharged on the third day after the procedure, and two patients were discharged at 1 and 2 weeks, respectively. Blood transfusion was necessary in three patients because of hematoma at the incision site in two patients, which required surgical revision for hemostasis, and because of transoperative bleeding in one patient. Follow-up time ranged from 2 to 15 months. The only death occurred 5 days postoperatively as a consequence of ischemic colitis and multisystem organ failure in the only patient who required surgery. CONCLUSION Treatment of AAA with the TSG system is effective for aneurysm exclusion. This device seems to provide a good alternative to surgery in patients who are otherwise considered to be at high risk for complications after direct surgical repair, but it is not without risk of complications.

Modelos animais de aneurisma de aorta

Experimental animal models have been used in vascular surgery for decades. The development of new interventional techniques in the endovascular treatment of aneurysms requires the creation of good experimental models to test these devices and study their impact on disease progression. The aim of this article was to review arterial aneurysm models currently available. Several distinct models have been described but none of them satisfies all the requirements of an ideal aneurysm model. Large animal models are appropriate for training, study of alterations in physiological parameters during and after device delivery, and integration of this device in the vessel wall. Significant disadvantages include difficulty in handling, high costs, difficult maintenance, and government regulations, hindering the availability of several animal species. Small animal models, such as rabbits and mice, despite being inexpensive and easily available, are not appropriate for studies of endovascular techniques because of their small-diameter vessels. To date, none of the models described could mimic all features of human aneurysms. In this review, we describe the available models and discuss their advantages and limitations.

Atualização sobre endopróteses vasculares (stents): dos estudos experimentais à prática clínica

The treatment of peripheral vascular diseases is one of the most rapidly expanding fields of medicine today. The number of peripheral interventions increased and innovative endovascular techniques are close to the results of traditional vascular surgeries. Although balloon angioplasty alone offers good immediate results, implantation of stents has been proposed to improve the procedural success and extend its application to more patients with peripheral vascular disease. However, stenting is controversial. Use of stents has good results in aortoiliac vessels, but its use in femoropopliteal vessels is still in dispute. Moreover, the rapid development of endovascular stents for peripheral applications and their choice have been a complicated task for endovascular surgeons. Many factors influence choice of stent, therefore, knowledge of available stents is mandatory. Appropriate selection depends on adequate preprocedural evaluation of the lesion, choice of primary vs. selective stent placement, and location and characteristics of the lesion. In this article the history of stent development is reviewed, from studies with experimental models to clinical practice, and its application in the treatment of peripheral vascular diseases is discussed.

Ruptura dos vasa vasorum e hematoma intramural da aorta: um paradigma em mudança

Rupture of vasa varorum has been recognized as one cause of intramural hematoma of the aorta for 90 years. This brief revision presents systematically, the physiology of these vessels and its role in the physiopathology of the alterations in the aortic wall secondary to hypertension, arteriosclerosis and in Acute Aortic Syndrome. The hypothesis is that rupture of vasa vasorum is a secondary phenomenon and not one causal factor in the physiopathology of intramural hematoma.

Self-expandable nitinol stent placement in homocysteinemic porcine aorta

PURPOSE To compare aortic intimal thickening of normal and hyperhomocysteinemic pigs (induced with a methionine-rich diet) following placement of a self-expanding nitinol stent. METHODS Eighteen Macau pigs were used. They were older than eight weeks in age and had an average weight of 30 kg. Pigs were randomly divided into two groups. The first, Group C (control), was fed a regular diet, and the second group, Group M, was fed a methionine-rich diet for 30 days to induce hyperhomocysteinemia. The self-expandable nitinol stents were 25mm in length and 8 mm in diameter after expansion. Blood samples were collected to measure total cholesterol, triglycerides, HDL and homocysteine concentrations. All animals were subjected to angiography. Thirty days after the procedure, the animals were sacrificed, and the abdominal aorta was removed for histological and digital morphometry analysis. RESULTS Under microscopic evaluation, the intima was significantly thicker in Group C than in Group M. When groups were compared by digital morphometric analysis, intimal thickening of the vessel wall was higher in Group C than in Group M. There was no significant change in total cholesterol, triglycerides or HDL concentrations in either group. In group C the levels of plasma homocysteine ranged from 14,40 to 16,73μmol/l; in Group M, plasma homocysteine levels ranged from 17.47 to 59.80 μmol/l after 30 days of a methionine-rich diet. CONCLUSION Compared to normal pigs, less intimal hyperplasia was observed in the abdominal aortas of hyperhomocysteinemic pigs thirty days after the insertion of a self-expandable nitinol stent.

Modelo experimental de aneurisma sacular de artéria ilíaca comum com pericárdio bovino em suínos

Objective: To develop an experimental model of saccular pseudoaneurysm of the common iliac artery with bovine pericardium in pigs. Method: The animals used were two 30-kg female pigs from the Landrace specimen. The animals were submitted to general anesthesia and laparotomy with extraperitoneal access to infrarenal aorta and the iliac arteries. After systemic heparin and clamping, the iliac artery was opened and the pericardium sutured to the vessel wall. All animals were confined for 3 weeks and were sacrificed after performing an arteriography to verify the patency of the aneurysm. Result: All animals survived the procedure and the aneurysms were patent. No rupture was detected. Conclusion: This is a feasible pig model of iliac artery aneurysm with potential for further studies to develop new endovascular prostheses.

Efeitos a curto prazo de "stents" não recobertos e recobertos com politetrafluoroetileno em aorta de suínos: um modelo experimental

PURPOSE: To report an experimental study evaluating, through digital morphometry, the intimal thickening of the arterial wall after the implant of auto-expandable stainless steel stents covered or not with polytetrafluoroethylene (PTFE) in the pig aorta. METHODS: In three groups of pigs a 12 F sheath was inserted in distal abdominal aorta. Group I animals (n=5) served as control. Group II animals (n=10) received an auto-expandable uncovered metallic stent. On group III animals (n=10) an auto-expandable stent covered with PTFE was inserted. After four weeks the animals were killed, the specimens were harvested and the intimal thickening was quantified by morphometric analysis. RESULTS: In the comparison among groups I, II and III referring to intimal, medial area and intimal index, it was not observed statistically significant variation. Differences were identified among groups referring to luminal proximal (p=0,036) and distal areas (p=0,044). Through multiple comparison tests for Kruskal-Wallis it was identified a difference between groups I and II. However, when these variables were controlled by weigh factor (luminal area/weigh relation), this difference was not observed anymore. CONCLUSION: In this short term study, the PTFE covering is not associated to further intimal thickening besides that promoted by the metallic mesh in large arteries and in high flow conditions.

Aortomonoiliac Stent-Grafts for Abdominal Aortic Aneurysm Repair: Association with Iliofemoral Crossover Grafts

Purpose: To analyze the outcome of endovascular exclusion of abdominal aortic aneurysm (AAA) using aortomonoiliac stent-grafts. Methods: Fifty-seven consecutive patients (49 men; median age 70, range 56–89) with AAA >5 cm were treated in a 6-year period with the conical ELLA stent-graft. Forty-two (73.9%) patients were classified ASA (American Society of Anesthesiologists) IV and 6 as ASA V. In the majority of cases, the implantation procedure featured device delivery through the external iliac artery, transrenal placement of a bare stent in selected cases, and an iliofemoral crossover graft through a prevesical tunnel. Results: Successful deployment was achieved in 56 (98.2%) patients. Mean time to discharge was 8.7 days (range 2–125). Two patients died in the 30-day period. Nine endoleaks occurred in 8 (14%) patients; 4 required further intervention. Mean follow-up was 35.3 months (range 1–66), during which 5 patients died from unrelated causes. No late endoleak, graft occlusion, device twisting/migration, or aneurysm rupture was observed. No correlation between type I endoleaks and unfavorable proximal neck or iliac artery anatomical characteristics could be found. Primary technical and clinical success rates were 86.0% and 94.7%, respectively. Conclusions: In this approach, the crossover graft remains in a retropubic space and consequently does not have all the disadvantages of a subcutaneously placed prosthesis. The results achieved in this group of high-risk patients support recommendation of this technique as a simple and safe alternative to bifurcated systems.

Morphometric analysis of intimal thickening secondary to stent placement in pig carotid arteries

OBJECTIVE To evaluate intimal thickening secondary to stent placement or to insertion of the delivery system without stent placement in pig carotid arteries. METHODS Stents were placed in the right common carotid arteries of 7 pigs, and 7 other control pigs underwent only insertion of the delivery system without stent placement. Uninjured contralateral common carotid arteries of the two groups were also used as controls. Samples of arterial tissue, obtained from the area adjacent to the distal segment of the stent four weeks after placement, underwent morphometric analysis. Morphometric data were compared with findings for arterial samples from injured arteries of the control group and uninjured contralateral arteries of the two groups. The unpaired Mann-Whitney U test and the Wilcoxon t test for nonparametric samples were used for statistical analysis. RESULTS Greater intimal thickening was found in the group in which stents were placed (p=0.008). Changes in luminal area and media layer were not significantly different between the two groups. The comparison of contralateral carotid arteries of the two groups revealed significant changes in intimal and luminal areas. No statistically significant changes were found in medial layer area. CONCLUSIONS All arteries that underwent stent placement showed intimal thickening without changes in the tunica media at four weeks. Dissection and insertion of the delivery system without stent placement was associated with a lesser degree of intimal thickening.

Anatomia microcirúrgica da artéria carótida externa: um estudo estereoscópico

CONTEXTO: O conhecimento das estruturas anatomicas da arteria carotida externa por meio do estudo estereoscopico pode determinar melhores resultados em microcirurgias da arteria carotida externa. OBJETIVO: Descrever as estruturas da arteria carotida externa sob a visao estereoscopica, identificando seus multiplos aspectos. METODOS: Doze regioes cervicais foram dissecadas, utilizando-se microscopico cirurgico com 3 a 40x de aumento. As disseccoes anatomicas foram documentadas utilizando-se a tecnica para obtencao de imagens tridimensionais (3D), objetivando a producao de impressoes estereoscopicas. RESULTADOS: O uso da tecnica estereoscopica possibilitou a abordagem da circulacao arterial extracraniana, sendo realizados estudos cirurgicos do tipo combinado fossa posterior e fossa infratemporal, tornando as microcirurgias e os procedimentos neurocirurgicos vasculares mais precisos. CONCLUSAO: O uso das imagens obtidas pela tecnica estereoscopica produziu um resultado mais assertivo em relacao ao estudo da anatomia para a microcirurgia e procedimentos neurocirurgicos, facilitando melhor aprendizado previamente a realizacao de procedimentos complexos em neurocirurgia.